Institute of Fundamental Technological Research

This paper introduces a first-time investigation into the impact of power ultrasound (PUS)-assisted preparation on the physicochemical and mechanical properties of cement-granulated blast furnace slag (GBFS) composite pastes. Pastes containing deposited GFBS with varying particle size fractions, partially replacing Portland cement, were prepared using PUS (ultrasonic horn tip, 20 kHz, 700 W) in pulse mode in a vertical jacketed glass sonoreactor with closed-circuit cooling. Cement paste incorporating 20 wt.% GBFS as mass substitution with varying particle size fractions was characterized by several physicochemical techniques at different curing ages. Exploring the cement and GBFS interaction induced by PUS, the compressive and flexural strength, the elastic modulus and indentation hardness, the heat of hardening, the mineral composition of hydration products, and the specific surface area BET were evaluated for a curing time of up to 28 days. The grain size distribution of GFBS and the reaction mixture's pH were measured. Both mechanical properties, heat of hydration and nanoporosity exhibited strong sensitivity to PUS treatment. Sonofragmentation of GBFS particles (especially the 125–250 μm fraction) increased with increasing sonication time, resulting in a relative increase of fraction <63 μm and a decrease of fraction >125 μm by 275 % and 60 %, respectively. Using the obtained SEM-EDS data, a simplified mechanism is proposed to explain the effects induced by PUS treatment.

Power ultrasound treatment, Portland cement, Granulated blast furnace slag, Early strength development, C-S-H/C-A-S-H, Seeding effect

Exposed aggregate concrete (EAC) pavement is a commonly employed technology in Europe for the construction of highways. The technical challenges associated with pavement construction include achieving both a comfortable ride and the desired skid resistance, while ensuring the long-term concrete durability. Maintaining uniformity of concrete mix, precise dosing of retarding agents, optimal selection of brushing time, and ensuring adequate curing conditions are identified as critical factors for achieving the designed ride performance. This study is focused on determining the appropriate time for the brushing operation, conducted to expose aggregate grains at the surface of the pavement. Laboratory tests were performed on concrete mixes designed to replicate job mixes for the upper layer of a two-layer concrete pavement. Measurements of the mass of evaporated water from the cement paste, isothermal calorimetry tests, and modified Vicat tests were employed to predict the appropriate brushing time. The texture depth was determined using a laser profiler as a function of brushing time. Compressive strength, the rate of chloride ion migration, and scaling resistance were determined through tests conducted on specimens cut from exposed aggregate slabs. Results revealed the suitability of the developed test method for determining the appropriate time for brushing EAC pavements.

cement setting, exposed aggregate concrete, macrotexture, pavement durability, surface retarder, texturing technology

The wide use of multi-component cement of highly reduced Portland clinker factor is largely impeded by detrimental changes in the rheological properties of concrete mixes, a substantial reduction in the early rate of cement hardening, and sometimes the insufficient strength of mature concrete. Therefore, major changes are needed in traditional concrete-production technologies if low-clinker cement is to gain wider acceptance. This review’s goal is to summarize the impacts of using non-ionizing radiation methods to improve the dispersion of concrete mix constituents, cement setting, and early hardening. The potential impacts of such interactions on the permeability and strength of concrete are also highlighted and investigated. Their intriguing potential for delivering additional energy to cementitious mixtures is analyzed for batch water, solid non-clinker constituents of cement (mainly supplementary cementitious materials), and their mixtures with aggregates. The advantages of adopting these non-traditional methods are found to be highly alluring to the greener preparation techniques used in the construction materials sector.

concrete mixing technology,early-age properties,low-clinker multi-component cement,magnetized water,microwave treatment,non-clinker constituents,ultrasound treatment

The article presents the diagnostic results on surface-hardened industrial concrete floors. Selected examples of floors showcased premature damage to surface layers, characterized by intense dusting, delamination, and local spalling, while the structural system remained unaffected. Quantitative petrographic analysis of concrete was applied to core specimens from the floors, involving the examination of digital images from a polarizing optical microscope and a scanning electron microscope. The hardening compound and powdered specimens of the cement matrix were characterized using differential thermal analysis and X-ray diffraction. A multiple microindentation method was employed to assess local variations in mechanical properties. Concrete cross-section analysis revealed areas with a non-uniform distribution of air voids, identified regions exhibiting increased porosity, highlighted areas of cracking in the concrete, indicated local variability in the phase composition of cement hydration products, and pointed out the presence of carbonated areas. The causes of the damage were discussed based on these findings,. The crucial role of quantitative petrographic analysis in diagnosing premature surface damage to industrial floors was demonstrated.

concrete, delamination, quantitative microscopy, porosity, industrial floors, dusting, surface hardening

Przedstawiono wyniki oceny diagnostycznej posadzki przemysłowej przy wykorzystaniu metodyki ilościowej oceny mikrostruktury betonu. Objawy uszkodzeń obejmowały pylenie powierzchniowe i delaminację warstwy utwardzonej. Przeprowadzono analizę petrograficzną składu betonu w próbkach-odwiertach. Zaobserwowano nadmierne napowietrzenie betonu, gromadzenie się porów powietrznych i występowanie ukierunkowanych spękań, miejscową zmienność składu fazowego produktów hydratacji cementu, w tym występowanie obszarów o intensywnej karbonatyzacji, co wpływało na przedwczesne uszkodzenia powierzchniowe.
Diagnostic assessment of industrial floor using the methodology of quantitative evaluation of concrete microstructure is presented. Symptoms of damage included surface dusting and delamination of the top layer. A petrographic analysis of the concrete composition in core specimens was carried out. Excessive air content, accumulation of air voids and the occurrence of oriented cracks, local variability of the phase composition of cement hydration products, including the occurrence of carbonated areas were observed and associated with the premature surface damage.

delaminacja, mikroskopia ilościowa, porowatość, posadzki betonowe, utwardzenie powierzchniowe, delamination, quantitative microscopy, porosity, concrete floors, surface hardening

Supersulfated cement (SSC) is a traditional low-carbon cement, but its slow hydration and strength development has limited its practical applications. Nano silica (NS) was used to activate the hydration of SSC by taking advantage of its ability to regulate silicate and aluminate reactions. The mechanical performance of various mixes was determined, as a function of sulfation degree and NS addition, as pore structure, phase assemblage, hydration degree, and microstructure. Results showed that NS improves the hydration degree of slag, densifies the microstructure, and significantly increases both early- and late-age compressive strength. The enhancement was attributed to its effects on the hydration of slag in SSC: delaying ettringite formation, but promoting C-(A)-S-H precipitation, reducing microporosity. This study reveals the critical role of the regulation of hydration kinetics of silicate and aluminate in controlling the performance of SSC as NS does.

Supersulfated cement, Nano silica, Gypsum content, Mechanical property, Microstructure

Expressway and highway pavements are exposed to intensive impacts of exploitation, including heavy vehicle traffic and environmental factors such as temperature and moisture along with the aggression of de-icing agents. Proper selection of mineral aggregates and design of the concrete mixture composition are important for the durability of the concrete pavement. Experimental tests were conducted on concrete under simulated service exposure conditions with external exposure to a 3% sodium chloride solution. The subject of the research was the expansion and elastic properties of air-entrained concrete made with siliceous aggregates from rocks containing moderate amounts of reactive minerals. The category of reactivity of coarse aggregates was uncertain, and in the fine aggregate was moderately reactive quartz sand. Under simulated service exposure conditions on road pavements, the significant expansion of concrete specimens and a significant decrease in the resonance elastic modulus up to 12.5% were observed. The tendency of concrete to expand was related to the presence of reaction products of reactive silica in the aggregate grains with sodium and potassium hydroxides in the cement paste [ASR], confirmed by microscopic observations. Replacement of Portland cement with CEM II/A-V 42.5 N cement and CEM II/B-S 42.5 N cement significantly reduced concrete expansion and improved the stability of elastic properties. In two of the nine concrete mixtures, the selected content of siliceous fly ash and granulated blast furnace slag, 18% and 30%, respectively, turned out to be sufficient to counteract the deleterious effects of the ASR under conditions of external contact with sodium chloride solution. A practical method for predicting the durability of concrete in the conditions in which the reactivity category of the aggregate from local natural resources is uncertain was established.

air-entrained concrete, cements with mineral additives, aggregate corrosion, alkali-silica reaction, simulated service exposure conditions, durability of paving concrete, external influence of sodium chloride

A review of concrete durability at several sections of the new built expressways in Poland is presented. Two-layers jointed plain concrete pavements were constructed using a slip-form technology. For freeze-thaw and deicing salts durability of concrete the specified air void properties, including the spacing factor and the microvoids content, was evaluated on core specimens drilled from the constructed pavements. The observed system of fine air voids indicates optimal features for increased frost and scaling resistance without a significant negative impact on strength. The correlation was established between the microvoid content in the hardened concrete and the data of the Super Air Metre on fresh concrete mix was established. Concrete durability in high moisture environment, combined with fatigue traffic load and external supply of alkaline deicing salt solutions, was considered using newly developed principles of nonreactive aggregate selection. The aggregate selection based on petrographic analysis and the assessment of expansive behaviour of concrete was fully confirmed using the performance tests with external supply of sodium chloride. The suitability of the established methodology for durability acceptance testing for exploration of alternative materials for paving is discussed.

air voids, durability, jointed plain concrete pavement, materials selection, performance test

Potential use of marginal fine aggregate in concrete is hindered by prescriptive quality requirements for concrete constituents. Experimental tests were performed on eleven mixtures of coarse and fine aggregates of variable susceptibility to alkali silica reaction (ASR). The miniature concrete prism test was applied for evaluation of ASR-induced expansion and associated changes of elastic properties were evaluated using the resonance modulus testing. Substitution of nonreactive sand with sands of moderate reactivity resulted in a relative increase in concrete expansion by 19–112% and substantial reduction of its elastic properties during the exposure to accelerated ASR environment. The Kolmogorov-Avrami-Mehl-Johnson model, modified to incorporate separately the effects of moderate reactivity of coarse and fine aggregate fractions, successfully described the kinetics of ASR-induced expansion. Beneficial effects of blastfurnace slag used for partial replacement of Portland clinker in blended cements were captured for aggregate combinations.

Aggregate mixture reactivity, Alkali-silica reaction, Fine aggregate, Kinetic model, Miniature concrete prism test, Slag-blended cement

The combination of MCNP6 and the FISPACT codes was used to predict inventories of radioisotopes produced by neutron exposure of a sample in a research reactor. The detailed MCNP6 model of the Budapest Research Reactor and the specific irradiation geometry of the NAA channel was established, while realistic material cards were specified based on concentrations measured by PGAA and NAA, considering the precursor elements of all significant radioisotopes. The energy- and spatial distributions of the neutron field calculated by MCNP6 were transferred to FISPACT, and the resulting activities were validated against those measured using neutron-irradiated small and bulky targets. This approach is general enough to handle different target materials, shapes, and irradiation conditions. A general agreement within 10% has been achieved. Moreover, the method can also be made applicable to predict the activation properties of the near-vessel concrete of existing nuclear installations or assist in the optimal construction of new nuclear power plant units.

MCNP6,Monte Carlo simulations,FISPACT,Isotope inventory,Radioisotope production,Neutron activation analysis,Mineral aggregate,Radiation shielding concrete

The long term durability of concrete pavements in wet-freeze climate is influenced by deicing salts used for winter maintenance of roads. Alkaline deicers could also be an external source of alkalis therefore their role in respect to development of deleterious alkali-silica reaction (ASR) should be considered. The performance of mineral aggregate mixtures in concrete was studied using RILEM test procedure ‘60°C concrete test with external alkali supply’. Air entrained concrete specimens were exposed to cyclic temperature changes, wetting-drying and NaCl solution immersion. Tests revealed the development of concrete expansion in time and associated changes of its elastic modulus for 31 mixtures of fine and coarse aggregate and Portland and fly ash or slag blended cements. The expansive behavior of air entrained concrete was strongly influenced by the presence of micro- and cryptocrystalline silica in aggregates. A replacement of nonreactive limestone sand by moderately reactive quartz sand resulted in a substantial enhancement of concrete expansion by a factor of three. Observed reduction of elastic modulus was correlated with more abundant presence of alkali-silica reaction products in concrete. Effects of cement type (CEM I, CEM II/A-V and CEM II/B-S) on the ASR performance of concrete with crushed coarse aggregate and quartz sand are discussed.

Air entrained concrete,alkali-silica reaction,external alkalis,NaCl solution,performance test

Current insulation materials applied in construction engineering and the building industry are generally petrochemical-based polymers and recycled thermal insulation materials. The environmental effects of these materials’ production processes aresubstantial, despite their high thermal insulation performance. Consequently, the researchers conclude that it is essential to develop and produce insulating materials with superior thermal properties, minimal environmental impact, and a reasonable cost. The study concentrated on the application of insulation materials derived from biomass in the development of thermal insulation. The purpose of this review is to investigate and develop the possibilities of using biomass wastes as renewable and eco-friendly thermal insulation materials for construction engineering and the building industry. The thermal conductivity of those materials was measured using the hot plate and hot box methods, two of the most widely used hot processing methods. With a relatively low thermal conductivity (< 0.100 W·m−1·K−1), this review provides critical scientific insight into potential building insulation materials derived from biodegradable and abundant resources. It was observed that these materials are appealing for use in building and construction because they have a number of potential advantages from technical, economic, environmental, and green credentials perspectives. The collection of information enables some conclusions regarding the different biomass waste–derived insulation materials that have already been investigated and identifies gaps in the literature. Finally, the scope of commercialization pathways and future research directions to validate the proposed material alternatives’ claim for commercial-scale applications has been identified in this review

Thermal conductivity,Building insulation materials,Biomass valorization,Hot plate method,Hot box method

This article examines the problem of the service life of reinforced concrete structures intended for nuclear power plants and radiation waste storage bunkers when exposed to radiation. This research focused on assessing the corrosion resistance of steel bars under conditions of simultaneous exposure to gamma radiation and various environmental conditions affecting the rate of carbonation. Electrochemical measurements of steel bars were carried out on samples in three environmental conditions: in a laboratory–dry; enclosed in a can at RH = 50%; and enclosed in a can at RH = 100%. The durability of the passivation layer of steel on non-irradiated and irradiated specimens after 8 months of exposure to gamma radiation was compared. A lower degradation effect of gamma radiation was visible in fully water-saturated specimens

corrosion of steel, relative humidity variability, carbonation condition, EIS, polarization curve

For possible application of gamma radiation in processing of fresh concrete, like surface processing at precast plants or 3D printing, it is essential to evaluate effects of irradiation on the early hardening of cementitious binders. The influence of gamma irradiation with the dose rate of 4.6 kGy/h on the early strength, pore size distribution and qualitative phase composition of mortar was investigated. The range of investigation comprises the effects selected micro- and nano-additions to Portland cement mortar used to control the kinetic of setting and early hardening of cement. Results show that gamma irradiation of hardening mortar results in the early strength increase of about 56–100%, in reduction of capillary porosity and pore size refinement. The gamma-irradiation sensitivity of early strength of cement mortar is equivalent to increased temperature wet curing. A correlation of heat evolution characteristics of hardening mortar and the temperature-equivalent of gamma irradiation is discussed.

boron minerals, early hardening, gamma irradiation, pore size distribution, strength, temperature equivalent

Concrete mix design for radiation shielding is mainly based on selection of aggregate materials of specified elemental composition. Serpentinite aggregate could be a desirable component of concrete for mixed-radiation attenuation and for high temperatures, however its durability performance needs further attention. The objective of the study is to reveal the influence of serpentinite aggregate on the microstructure and transport properties of baryte-serpentinite concrete. Mix design was developed for low-heat Portland cement and slag cement by using a combination of serpentinite aggregate and baryte aggregate. The compressive strength, chloride migration coefficient, carbonation resistance were experimentally investigated. The durability tests were compared with open porosity, mercury intrusion porosimetry measurement and examination of thin section of concrete by optical microscope. The results revealed increased porosity of contact zone of serpentinite aggregate with cement matrix. Open and capillary porosity of concrete was found to increase with increase of serpentinite aggregate content. Consequently, an increase of the chloride migration coefficient up to 2.5 times, the rate of carbonation up to 4 times were observed.

baryte, serpentinite, carbonation, chloride ion permeability, durability, microstructure, mix design, interfacial transition zone, porosity, radiation shielding concrete

A viable prediction of service life of reinforced concrete structures exposed to irradiation environment is necessary to support a license extension for currently operating nuclear power plants as well as to support concrete mix optimization for new builds. An experimental study was carried out to evaluate the corrosion performance of mild steel reinforcing bars under gamma irradiation at environmental conditions favoring accelerated carbonation. in elevated temperature. The electrochemical impedance spectroscopy and potentiodynamic electrochemical tests were performed to assess the corrosion rates on the rebar surfaces. Effects of irradiation were also examined in regard to capillary pore size distribution by mercury intrusion porosimetry and mesopore distribution based on nitrogen desorption data. Companion tests were performed to determine the compressive and flexural strength of mortar exposed to gamma irradiation. Relative effects of gamma irradiation are reported for mortar specimens containing fly ash or limestone powder used for partial replacement of Portland cement up to 40% by mass. Gamma irradiation dose up to 2 MGy was found to affect the properties of passive layer of steel in comparison to non-irradiated specimens. A decrease of corrosive potential and passivation potential was found. An increase of corrosion current density by an order of magnitude due to gamma irradiation was observed. Parameters of polarization curves of steel indicated unstable passive layer on steel reinforcement in irradiated mortars.

gamma irradiation, steel corrosion, supplementary cementitious materials, modification, electrochemical impedance spectroscopy, corrosion potential, Barrett-Joyner-Halenda porosity

Prediction of carbonation progress in concrete exposed to ionizing radiation is important for the durability assessment of nuclear power plants, eventually needed for operational license extension. The objective of this work is to reveal the influence of gamma irradiation on the carbonation development and resulting microstructural features of cement mortar. The composition of mortar was varied by using mineral additions. Canned specimens at elevated CO2 concentration environment were exposed to gamma irradiation up to the absorbed dose of 1.6 MGy in the vicinity of spent nuclear fuel rods in pool of research reactor. Micromechanical properties of carbonation reaction products were determined using nanoindentation tests. The carbonation depth was found to increase with increasing absorbed γ dose. The size of calcite crystals was about three times greater in irradiated specimens. Gamma irradiation improved the micromechanical properties of carbonation products. Effects of mineral additives on the characteristics of irradiated mortar are discussed.

calcite, carbonation, cement mortar, gamma irradiation, microstructure, mineral additions, nanoindentation

Diagnostic tests were carried out on specimens drilled from a section of jointed, unreinforced highway pavement after 15 years of service. The section of highway was exposed to heavy road traffic, environmental actions of wet-freeze climate zone and associated winter maintenance including application of deicing salt. Premature pavement damage was manifested by visible cracking, mostly along transverse joints and in slab corners. Tests performed on core specimens included petrographic analysis of concrete and its components, using optical and scanning electron microscopy, also evaluation of elastic and transport properties, expansion potential, cracks and air void system. Numerous cracks in the grains of coarse quartzite aggregate were found. Reactive forms of quartz in quartzite aggregate - microcrystalline and cryptocrystalline quartz - were abundant. The gel-like products in cracks in quartzite grains and in surrounding cement paste were identified as alkali-silica reaction products. Expansion of specimens exposed to an alkali-silica reaction-promoting environment indicated the potential for further development of such reaction. Substantial cracking and reduction of modulus of elasticity was correlated with the presence of reactive quartz in quartzite aggregate. The role of additional destructive factors, such as the impact of heavy vehicles traffic and freeze-thaw aggression was indicated by greater cracks in the slow traffic lane compared than in the emergency lane, associated with local marginal air entrainment of concrete.

alkali-silica reaction, concrete, cracking, durability, highway pavement

Premature damage to the concrete pavement of a trunk road section after 15 years of its service life was noticed. The damage manifested itself in cracking along transverse joints and in the corners of slabs. Diagnostic investigations, covering a petrographic analysis of concrete and mineral aggregates by means of optical and scanning microscopy, an evaluation of the elastic properties, the degree of cracking and air-void parameters and an identification of the alkali-silica reaction products, were carried out on core samples. Multiple cracks in coarse quartzite aggregate particles and in cement matrix were found. A significant presence of microcrystalline and cryptocrystalline quartz in quartzite particles was detected. Typical alkali-silica reaction products were unambiguously identified. The considerable cracking and the substantial decrease in the modulus of elasticity were correlated with the presence of reactive quartz in the quartzite aggregate and the alkali-silica reaction was found to be the main cause of the damage. Additional damaging factors, such as heavy traffic loads and frost aggression, are discussed.

concrete, road pavement, pavement evaluation, aggregate, quartzite, alkali-silica reaction, cracks, service life

Artykuł przedstawia badania wpływu stosowania cementów z dodatkami mineralnymi CEM II/A-V 42,5 R, CEM II/B-S 42,5 N i CEM III/A 42,5 N na dystrybucję porów w mieszance betonowej przeznaczonej na górną warstwę nawierzchni betonowej zaprojektowanej na agresję środowiska XF4. Przeanalizowano zmiany charakterystyki porów w betonie od wykonania do wbudowania. Próbki pobrano bezpośrednio po wykonaniu mieszanki, po godzinie bezruchu i po wysokoenergetycznym mieszaniu po godzinie bezruchu. Określono charakterystykę porów, właściwości mieszanki betonowej oraz właściwości mechaniczne stwardniałego betonu. Przeanalizowano tendencje zmian całkowitej zawartości powietrza oraz zawartości mikroporów w betonie, wynikające z zastosowania cementu z dodatkami mineralnymi. Uzyskane wyniki świadczą o kompatybilności układu domieszek napowietrzającej i uplastyczniającej z użytymi rodzajami cementu.

The concrete microstructure was successfully reconstructed using the complementarity of X-ray and neutron computed tomography (CT). Neither tomogram alone was found to be suitable to properly describe the microstructure of concrete under this study. However, by merging the information revealed by the two modalities, and using image segmentation, noise reduction, and image registration techniques we reconstruct the concrete microstructure. Void, aggregate, and cement paste phases are successfully captured down to the images' spatial resolution, even though the aggregate consists of multiple minerals. The coarse-aggregate volume fraction of the reconstructed microstructure was similar to that of the mixing proportions. Furthermore, image-based finite element analysis is performed to demonstrate the effects of microstructure on stress concentration and strain localization.

concrete microstructure, X-ray tomography, neutron tomography, image segmentation, complementarity field, image-based analysis

High-fluidity and self-compacting concrete (SCC) mixes were developed using special aggregates for radiation-shielding concrete. The special aggregates comprised heavyweight and hydrous aggregates (crushed magnetite, crushed serpentine, and their mixtures), which were selected to provide an enhanced attenuation of gamma and neutron radiation, respectively. For the mixed concrete design with a bulk density of up to 3570 kg/m^3, two cement types were used: Portland cement CEM I and slag cement CEM III/A. The basic properties of the fresh self-compacting concrete were evaluated and the lateral formwork pressure exerted by the freshly mixed self-compacting concrete was measured and analyzed. An original test setup was developed for the determination of the lateral pressure on the square column formwork with pressure measurements carried out using six strain gauge pressure transducers, which was adequate for heavyweight concrete mixture testing. Self-compacting concrete mixtures containing a magnetite aggregate or blends of serpentine and magnetite aggregates with a slump flow of at least 550 mm were developed. The lateral pressure on the formwork was directly proportional to the density of the self-compacting heavyweight concrete mixes. The maximum values of the lateral pressure recorded in the test at a casting speed of 1.5 m/h did not exceed 27 kPa and 55% of hydrostatic pressure. Concrete mixtures with basalt, magnetite, and magnetite/serpentine blended aggregates were found to develop sufficient shear strength for proper stability during casting.

Portland cement, consistency, formwork pressure, fresh mix, magnetite aggregate, mix design, radiation-shielding concrete, self-compacting concrete, serpentine aggregate, slag cement

The design of concrete for radiation shielding structures is principally based on the selection of materials of adequate elemental composition and mix proportioning to achieve the long-term durability in nuclear environment. Concrete elements may become radioactive through exposure to neutron radiation from the nuclear reactor. A selection of constituent materials of greatly reduced content of long-lived residual radioisotopes would reduce the volume of low-level waste during plant decommissioning. The objective of this investigation is an assessment of trace elements with a large activation cross section in concrete constituents and simultaneous evaluation of susceptibility of concrete to detrimental alkali-silica reaction. Two isotopes 60Co and 152Eu were chosen as the dominant long-lived residual radioisotopes and evaluated using neutron activation analysis. The influence of selected mineral aggregates on the expansion due to alkali-silica reaction was tested. The content of 60Co and 152Eu activated by neutron radiation in fine and coarse aggregates, as well as in four types of Portland cement, is presented and discussed in respect to the chemical composition and rock origin. Conflicting results were obtained for quartzite coarse aggregate and siliceous river sand that, despite a low content, 60Co and 152Eu exhibited a high susceptibility to alkali-silica reaction in Portland cement concrete. The obtained results facilitate a multicriteria selection of constituents for radiation-shielding concrete.

alkali-silica reaction, concrete durability, low-level radioactive waste, neutron activation analysis, radiation shielding concrete, trace elements

The kinetics of heat transfer in hardening concrete is a key issue in engineering practice for erecting massive concrete structures. Prediction of the temperature fields in early age concrete should allow for proper control of the construction process to minimize temperature gradients and the peak temperatures, which is of particular importance for concrete durability. The paper presents a method of identification of the thermophysical parameters of early age concrete such as the thermal conductivity, the specific heat, and the heat generated by cement hydration in time. Proper numerical models of transient heat conduction problems were formulated by means of finite-element method, including two types of heat losses. The developed experimental–numerical approach included the transient temperature measurements in an isolated tube device and an in-house implementation of an evolutionary algorithm to solve the parameter identification task. Parametric Bezier curves were proposed to model heat source function, which allowed for identifying such function as a smooth curve utilizing a small number of parameters. Numerical identification tasks were solved for experimental data acquired on hardening concrete mixes differing in the type of cement and type of mineral aggregate, demonstrating the effectiveness of the proposed method (the mean-squared error less than 1 °C). The proposed approach allows for the identification of thermophysical parameters of early age concrete even for mixtures containing non-standard components while omitting drawbacks typical for classical optimization methods.

early age concrete, evolutionary algorithm, inverse solution, heat transfer problem, mass concrete, thermal properties

The article describes an experimental study of the properties of concrete designed for the construction of the bottom layer of two-layered road pavement with the exposed aggregate surface. Two types of materials were studied: industrially-produced concrete placed on a highway trial section using slip form technology and concrete produced in a laboratory setting, containing CEM II/A-V and CEM II/A-S Portland cement. The tested mixes contained granite or limestone coarse aggregate. The following basic performance properties were studied: compressive strength and split tensile strength, air void characteristics, freeze-thaw resistance, water absorption rate and chloride penetration. The mechanical properties and freeze-thaw resistance results obtained on the laboratory specimens were similar to those obtained on the cores drilled from the pavement. Despite the observed changes in the air void system parameters, mineral admixtures to Portland cements did not reduce the freeze-thaw resistance of concrete. The compressive strength was higher by up to 19% and sorptivity decreased by up to 22% in concrete containing cement with mineral admixtures.

air-entrained concrete, air void characteristics, CEM I, CEM II/A-S, CEM II/A-V, durability, freeze-thaw resistance, road pavement, sorptivity

The effects of gamma irradiation on concrete properties during early hardening were studied towards radioactive waste storage or accelerated processing at precast plants. Concrete mixtures containing different mineral aggregates (baryte, magnetite, amphibolite) were investigated. During initial 16 hours of hardening the mixes were irradiated using 60Co gamma source at the rate of 3.5 kGy/h. The mechanical properties and microstructural features of irradiated early-age concrete were tested: the secant elastic modulus, the compressive strength, the porosity and pore size distribution. XRD and SEM analysis were also performed. The results indicate both the stiffening and pore refinement in concrete due to early gamma irradiation. Effects of early irradiation on microstructural features of cement matrix were found in the subsurface layer up to the depth of 2 mm. The influence of different mineral aggregates in concrete on the radiation-induced changes of early age properties is discussed.

Durability of concrete designed for radiation shielding structures is an important issue in nuclear power plant safety. An investigation of the permeability of concrete containing heavyweight aggregates and water-bearing aggregates was performed with respect to gaseous and liquid media. Mix design was developed using Portland and slag cement, crushed magnetite and serpentine aggregate. The use of slag cement in concrete containing magnetite and serpentine aggregates resulted in the substantial improvement of the compressive strength in comparison with Portland cement concrete. The application of slag cement was found to reduce the chloride ingress, regardless of the special aggregate use. The coefficient of chloride migration was within the range 5 ÷ 8 × 10^−12 m^2/s and 17 ÷ 25 × 10^−12 m^2/s for slag cement concrete and Portland cement concrete, respectively. At the same time, the carbonation depth was increased twice for slag cement concrete in comparison to Portland cement concrete. However, the maximum carbonation depth after one year of exposure to 1% CO2 was only 14 mm for slag cement concrete, and 7 mm for reference concrete. The total pore volume evaluated using mercury intrusion porosimetry was influenced by the type of special aggregate used. It was shown that concrete with various contents of magnetite aggregate and slag cement achieved the smallest total pore volume. While serpentine coarse aggregate caused an increase in total pore volume in comparison to concrete with magnetite aggregate.

chloride permeability, carbonation, slag cement, radiation shielding concrete, microstructure, MIP, mix design, Portland cement, magnetite

Zgodnie z definicją podaną w MEPDG 2020, równość nawierzchni odzwierciedla profil nawierzchni w śladach kół. W artykule przestawiono przegląd materiałowych i technologicznych czynników wpływających na równość nawierzchni drogowej z betonu cementowego, dyblowanej i kotwionej, przeznaczonej do kategorii ruchu KR5-KR7. Omówiono specyfikę metody ślizgowej, która jest procesem ekstruzji betonu, pozwalającym na monolityczne ułożenie warstwy przy jednym przejeździe układarki. Omówiono właściwości reologiczne mieszanki betonowej oraz jej praktyczne cechy techniczne, mające decydujące znaczenie przy formowaniu powierzchni jezdni.Utrzymanie stałego profilu nawierzchni w projektowanym 30-letnim okresie eksploatacji jest możliwe dzięki wysokiej odporności betonu na silne oddziaływania mechaniczne, termiczne i agresję środowiska.
According to the definition given in MEPDG 2020, the evenness of pavement reflects the surface profile in the wheel tracks. A review of material and technological factors influencing the evenness of the road pavement made of cement concrete, doweled and anchored, designed for traffic category KR5-KR7 is presented. The specificity of the slip-form method, which is a process of concrete extrusion, allowing for monolithic paving at one pass of the paver is discussed. Rheological properties of the concrete mixture and its practical technical features, which are decisive for the formation of roadway surface, are discussed. Maintaining a constant surface profile over the designed 30-year service life is possible due to the high resistance of concrete to strong mechanical, thermal and environmental influences.

beton cementowy, IRI, MEPDG, metoda ślizgowa, nawierzchnia drogowa, projektowanie składu, równość, trwałość, właściwosci reologiczne / cement concrete, IRI, MEPDG, sliding method, road pavement, composition design, evenness, durability, rheological properties

The procedure of numerical identification of thermophysical properties of concrete during its hardening is presented. Heat of cement hydration, thermal conductivity and specific heat are determined for purpose of modelling temperature evolution in massive concrete elements. The developed method is based on point temperature measurements in a cylindrical mould and the numerical solution of the inverse heat transfer problem by means of direct search optimization algorithm. The determined thermal characteristics of concrete are not constant and depend on the maturity of concrete. The procedure was verified on set of concrete mixes designed with Portland cement CEM I 42.5R and Portland-slag cement CEM II/B-S 32.5 N. Calcareous fly ash was also used for partial replacement of cement in the mixtures. The obtained results have been compared with experimentally measured temperature in concrete and a fair agreement has been found.

Results of measurements of the specific heat and the thermal conductivity of concrete with blended special aggregate for neutron and gamma radiation shielding are presented. Experimental tests were performed on concrete with heavyweight aggregate (magnetite, barite), hydrogen-bearing aggregate (serpentine) and amphibolite aggregate. The thermal properties of concrete were determined using a nonstationary method. The highest specific heat was found for concrete with serpentine aggregate. Simple models for predicting the specific heat and the thermal conductivity on the basis of concrete mix design were evaluated to include the blends of heavyweight and hydrogen-bearing aggregates. The thermal conductivity of concrete was found to be linearly dependent on the concrete density in the range from 2200 to 3500 kg/m3. Its increase due to water saturation of concrete was not dependent on the open porosity of concrete. It was found that the specific heat can be fairly well predicted using the rule of mixtures formula. The thermal conductivity of concrete can be approximately predicted using a parallel model in the case of water-saturated concrete. The thermal conductivity prediction for dry concrete is also discussed.

blended aggregate, concrete mix design, density, non-stationary method, open porosity, thermal properties, thermal conductivity, specific heat, radiation shielding

Fly ashes from coal combustion in circulating fluidized bed boilers in three power plants were tested as a potential additive to cement binder in concrete. The phase composition and microstructure of cement pastes containing fluidized bed fly ash was studied. The fractions of cement substitution with fluidized bed fly ash were 20% and 30% by weight. X-ray diffraction (XRD) tests and thermal analyses (derivative thermogravimetry (DTG), differential thermal analysis (DTA) and thermogravimetry (TG)) were performed on ash specimens and on hardened cement paste specimens matured in water for up to 400 days. Quantitative evaluation of the phase composition as a function of fluidized bed fly ash content revealed significant changes in portlandite content and only moderate changes in the content of ettringite.

clean coal combustion, fluidized bed fly ash, microstructure, phase composition, portlandite, unburned carbon

Gadolinium oxide (Gd2O3) is a potentially effective mineral additive that improves neutron shielding properties of cement based composites. The paper presents the influence of Gd2O3 and ulexite (a boron compound) on Portland cement hydration evaluated by isothermal calorimetry measurements and strength. The progress of hydration was investigated on mortar specimens at water to cement ratio w/c = 0.5 and sand/cement ratio 0.75. The addition of Gd2O3 generates a slight retardation of cement hydration, however it accelerates aluminate activity at the same time. The hydration of cement was completely hindered for mortars containing a substantial content of ulexite. The strength test results show that addition of Gd2O3 to Portland cement mortar mix caused a decrease of early age (3 days) flexural and compressive strength. The optimum content of Gd2O3 in respect to the long term compressive strength and the hydration kinetics was 5% in relation to the mass of cement. Good long term strength was also obtained for specimens with 3% of ulexite.

gadolinium oxide, boron compounds, isothermal calorimetry, bending strength, compressive strength, mortar, neutron radiation, radiation shielding, radioactive waste

The paper presents the results of the study of the influence of the addition of retarding superplasticising admixture based on triisobutyl phosphate and modified phosphonates on the amount of heat generated by hardening shielding concrete. A four-point measurement of the heat generated during the hardening of concrete with an admixture dose of 0, 0.5, 1.0 and 2.0% by weight of the cement was made and the concurrent measurement of the heat released by the hardening cement paste was measured with an isothermal calorimeter. Based on the results from the calorimeter, the effect of the admixture on the temperature field in the hardening concrete mass elements was simulated for different aggregates. The results indicate that the admixture clearly lowers the temperature gradient in hardening mass concrete. In the simulations, the most clear effect was achieved in the case of concrete with barite aggregate, where the gradient value was reduced from 10°C/m to 8°C/m for an admixture content equal to 2.0%.

temperature gradient, heat release, shielding concrete, mass concrete, fresh concrete, phosphorus compounds

The suitability of the sequential air pressure method (SAM) to evaluate the quality of air entrainment in concrete mix to support prediction of durability of hardened concrete was studied. The experiments included both laboratory-produced mixes and on-site trials on mixes delivered for highway pavement construction. The fresh air content and the air void distribution was tested using the SAM apparatus. The air content and the air void characteristics in hardened concrete was tested using the microscopic analysis on polished sections. Standard fresh mix properties were also tested and the compressive strength and salt-scaling resistance of concrete was determined. Effects of type and proportion of admixtures, type of crushed aggregate, timing of SAM measurements and the method of mix consolidation were analyzed. The relationship between the SAM number and the air void characteristics in hardened concrete was critically evaluated. The relationship between SAM number and the content of microvoids (A300) is found for the laboratory mixes and confirmed with few field test results. The criterion of SAM number ≤ 0.4 is proposed for the target microvoids content A300 ≥ 1.5% and the enhanced salt scaling resistance of concrete.

air entrainment, air void distribution, concrete durability, fresh concrete, frost-salt scaling, microvoids content, mix design, sequential pressure method, spacing factor, test methods

The paper presents the results of investigations into the reactivity of domestic aggregates produced from selected sedimentary rocks, carried out using the new testing methods, consistent with the RILEM and ASTM methods, implemented by GDDKiA (Polish General Directorate for National Roads and Motorways) documents. The range of the investigations covered coarse crushed aggregates produced from limestone, dolomite, sandstone and greywacke rocks, potentially suitable for making strong and durable concrete. No reactive forms of quartz were found in the mineralogical composition of the limestone aggregates and the dolomite aggregates. Micro- and cryptocrystalline quartz occurred in the particles of the greywacke aggregates and the sandstone aggregates. On the basis of the expansion of mortar and concrete specimens the aggregates produced from the sedimentary rocks were classified into the reactivity categories: R0, R1 and R2. A sodium-potassium-calcium silicate gel, whose composition (consistent with that reported in the literature) was characteristic of the alkali-silica reaction products, was found. The investigations resulted in a consistent assessment of the reactivity of the aggregates.
W pracy przedstawiono wyniki badań reaktywności krajowych kruszyw z wybranych, litych skał osadowych przy wykorzystaniu nowych metod badawczych wdrożonych w dokumentach technicznych Generalnej Dyrekcji Dróg Krajowych i Autostrad (GDDKiA), zgodnych z metodami RILEM i ASTM. Zakres badań obejmował kruszywa grube łamane o potencjalnej przydatności do wykonania wytrzymałego i trwałego betonu, wyprodukowane ze skał wapienia, dolomitu, piaskowca i szarogłazu. W składzie mineralnym kruszyw z wapieni i dolomitu nie stwierdzono obecności reaktywnych form kwarcu; w ziarnach kruszywa z szarogłazów i piaskowca występował kwarc mikro- i kryptokrystaliczny. Na podstawie wydłużenia próbek określono następujące kategorie reaktywności wybranych krajowych kruszyw ze skał osadowych: R0, R1 i R2. Zaobserwowano występowanie żelu krzemianu sodowo-potasowo-wapniowego o składzie charakterystycznym dla produktów reakcji alkalia-kruszywo, zgodnym z danymi literaturowymi. Uzyskano spójną ocenę reaktywności kruszyw.

alkali-aggregate reaction, cement, concrete, dolomite aggregate, expansion, greywacke, limestone, quartz, reactive minerals, sandstone / beton, cement, kruszywo dolomitowe, kruszywo wapienne, kwarc, minerały reaktywne, piaskowiec, reakcja alkalia-kruszywo, szarogłaz, wydłużenie

The paper presents investigations into the reactivity of aggregates from igneous rock, carried out in accordance with the procedures contained in the GDDKiA General Technical Specification "Concrete pavements". The aim of the investigations was evaluation of the suitability of the aggregates for road structures and pavements built using cement based concrete technology. Aggregates produced from extrusive rocks (basalt, melaphyre and porphyry) and from intrusive rocks (granite and gabbro) were analysed. The mineral composition of the aggregates was evaluated with regard to their reactive SiO2 content. Expansion tests on mortar bar and concrete prism specimens with analysed aggregates and a microscopic analysis of the alkali-aggregate reaction products were carried out. A considerable amount of reactive minerals: chalcedony, tridymite and microcrystalline quartz and volcanic glass were found in the grains of the porphyry and melaphyre aggregates. On the basis of the conducted investigations the two aggregates made of igneous rocks (melaphyre and porphyry) were classified into category R1 (moderately reactive). The basalt aggregate, the granite aggregate and the gabbro aggregate were assigned to category R0 (non-reactive).
W artykule przedstawiono badania reaktywności kruszyw ze skał magmowych przeprowadzone zgodnie z procedurami ujętymi w instrukcjach GDDKiA OST "Nawierzchnie betonowe" w celu oceny ich przydatności do stosowania w technologii betonu cementowego na drogowe konstrukcje inżynierskie i nawierzchnie. Analizie poddano kruszywa ze skał wylewnych: bazalt, melafir i porfir oraz ze skał głębinowych: granit i gabro. Przeprowadzono ocenę składu mineralnego kruszyw z uwagi na zawartość reaktywnych minerałów krzemionkowych. Przeprowadzono badania wydłużenia próbek zapraw i betonów z kruszywami oraz analizę mikroskopową produktów reakcji alkalia-kruszywo. Stwierdzono występowanie znacznej ilości reaktywnych minerałów w ziarnach kruszywa z porfiru i melafiru: chalcedonu i trydymitu oraz kwarcu mikrokrystalicznego i szkliwa wulkanicznego. Na podstawie przeprowadzonych badań dwa kruszywa ze skał magmowych (melafir oraz porfir) zaklasyfikowano do kategorii R1 - umiarkowanie reaktywne. Kruszywo bazaltowe, granit oraz gabro przypisano kategorii R0 - niereaktywne.

aggregate, alkali reactivity, alkali silica gel, cristobalite, igneous rocks, microcrystalline quartz, reactive minerals / alkaliczny żel krzemionkowy, kruszywo, krystobalit, mikrokrystaliczny kwarc, minerały reaktywne, reaktywność alkaliczna, skały wulkaniczne

Przemysł cementowy uznaje, że problem reaktywności to problem jakości kruszywa. Producenci kruszyw mineralnych uważają, że reaktywność jest problemem jakości cementu. A Komisja Europejska uważa, że najważniejszy jest wolny handel. Tak w skrócie można scharakteryzować stan normalizacji betonu i jego składników według Europejskiego Komitetu Normalizacyjnego CEN w zakresie bardzo istotnym dla zarządców i użytkowników obiektów betonowych, zwłaszcza nawierzchni kluczowych autostrad i mostów, projektowanych co najmniej na 50-100 lat użytkowania.

kruszywo, reaktywność kruszywa, beton, pęcznienie betonu, komitet techniczny RILEM

reaktywność kruszywa, obiekt betonowy, reakcja alkalia-krzemionka

Przestawiono analizę zagadnień projektowania składu betonu nawierzchniowego z kruszywem odkrytym, przeznaczonego na nawierzchnie drogowe o kategorii ruchu KR5-KR7. Omówiono wyniki badań betonu wykonanego w laboratorium w sposób imitujący wykonanie warstwy z kruszywem odkrytym. Wyznaczono wytrzymałość betonu, charakterystykę porów, szybkość absorpcji powierzchniowej wody i mrozoodporność powierzchniową w obecności roztworu chlorku sodu. Wyniki badań przeanalizowano w odniesieniu do zróżnicowania rodzaju cementu (CEM I, CEM III/A) i rodzaju pielęgnacji. Stwierdzono znaczący wzrost złuszczeń powierzchniowych i szybkości penetracji wody skorelowany z niedostatkiem pielęgnacji.

beton napowietrzony, charakterystyka porów, mrozoodporność, nawierzchnia drogowa dwuwarstwowa, pielęgnacja, przepuszczalność, warstwa z kruszywem odkrytym

Enhanced neutron radiation shielding capacity of protective structures can be achieved using cement-based composites with boron-containing aggregates. Experimental tests were performed to evaluate the effect of boron aggregates (colemanite, ulexite, borax, boron carbide) and nanosilica on the setting time and hydration heat of cement in mortars using isothermal calorimetry. Boron leaching test from mineral aggregates were performed in water and saturated Ca(OH)2 solution. Cement setting retardation effects were found qualitatively correlated with boron leaching from mineral aggregates. A linear dependence of compressive strength of borated mortars and heat released after 72 h of cement hydration was found. A maximum content of boron compounds in mortar, allowing for a systematical control of setting time, was evaluated

Boron minerals, Cement setting, Colemanite, Early strength, Heat of hydration, Isothermal calorimetry, Leaching, Nanosilica, Neutron shielding, Retardation, Ulexite

Long-term exposure of concrete to nuclear reactor environments may enhance the ageing phenomena. An investigation concerning a possible deleterious alkali-silica reaction (ASR) in concrete containing high-density aggregates is presented in this paper. The scope of this investigation was limited to heavy aggregates that could be used for the construction of the first Polish nuclear power plant (NPP). Five different high-density aggregates were selected and tested: three barites, magnetite, and hematite. Mineralogical analysis was conducted using thin section microscopic observation in transmitted light. The accelerated mortar beam test and the long-time concrete prism test were applied to estimate the susceptibility of heavy aggregates to ASR. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were conducted on aggregates and mortars. The quartz size in aggregate grains was evaluated using image analysis. Application of the accelerated mortar beam method confirmed the observations of thin sections and XRD analysis of high-density aggregates. The microcrystalline quartz in hematite aggregate and cristobalite in one of barite aggregate triggered an ASR. The composition of ASR gel was confirmed by microscopic analysis. The long-term concrete test permitted the selection of innocuous high-density aggregates from among the other aggregates available, which showed practically no reactivity.

alkali-silica reaction, heavyweight concrete, high-density aggregate, quartz size, radiation shielding, reactive minerals

The effect of the composition of industrial concrete designed for radiation shielding structures on the air permeability and the diffusion of moisture was studied. The mix design for heavyweight concrete of bulk density 3168–3317 kg/m3 was developed using barite and magnetite aggregate and cements blended with fly ash and blastfurnace slag. Structural elements, like columns of a height of 4 m and massive blocks made of mixtures with different cements were manufactured using ready mixed concrete pumped into the formwork. Core specimens were taken from the elements at different locations. The air permeability index was tested using Autoclam device. Evaluation of the quality of concrete on the basis of API results varied from “very good” to “good”. The moisture distribution inside concrete specimens was equilibrated to RH = 60 ± 5%. Observation of RH changes allowed to determine the moisture diffusion coefficient. Significant differences of the permeability and moisture diffusion coefficient depending on the location of the core specimens drilling and mix design of concrete were found. The D coefficient provided a good reflection of the different quality of heavyweight concrete in structural elements.

Air permeability, Autoclam, Barite, Blended cement, Cracking, Heavyweight aggregate, Magnetite, Moisture diffusion, Radiation shielding concrete, Relative humidity

This paper features the development of a probabilistic model linking freeze–thaw (F-T) performance of concrete mixtures to their composition. A sensitivity analysis was performed on several concrete mixture parameters to identify the factors that have strong correlations with F-T resistance of concrete. The F-T performance level was defined as a discrete measure of the frost resistance of concrete. Finally, a new model to predict F-T damage incorporating the variability in concrete mix parameters (as selected from sensitivity analysis) was developed. This model was developed using only those data sets that contained the results of the relative dynamic modulus of elasticity (RDME) testing performed according to ASTM and AASHTO specifications. Concrete mixtures containing only ordinary portland cement (OPC) as the sole binder (i.e., mixtures that did not contain any supplementary cementitious materials) were considered. The reliability of the model was demonstrated using several examples of concrete mixtures of various compositions. Accordingly, this model provides the opportunity to optimize the concrete mix proportion for the required performance level of concrete under F-T exposure condition.

Freeze–thaw, Durability, Concrete, Pavement, Sensitivity analysis, Probabilistic design

The permeation properties of concrete are strongly influenced by the degree of saturation of capillary pores. Test results of the Autoclam air permeability index (API) of radiation shielding concrete are presented. Concrete specimens were made with CEM I and CEM III/A cements and special aggregates for radiation shielding: crushed barite, magnetite, serpentine and amphibolite. Two procedures of accelerated drying with simultaneous measurement of moisture distribution in the specimens were proposed. The specimens were tested at different RH levels from a fully saturated state to an oven dried state. The linear relationship between the API and RH was obtained. Effects of heavyweight and hydrogen-bearing aggregates on air permeability index were revealed.

Autoclam air permeability, Relative humidity, Heavyweight aggregate, Barite, Magnetite, Serpentine, Radiation shielding concrete, Slag cement

Modelling studies in laboratory of the effect of curing on the mechanical properties and durability of the concrete pavement with exposed aggregate are presented. Air-entrained concrete was designed as the top layer of a motorway pavement with the use of two types of cements: CEM I and CEM III/A. The w/c increase (from 0.34 to 0.37) and change of cement type (CEM I 42.5N and CEM III/A 42.5 N) in properly air-entrained concrete did not influence significantly the internal frost resistance F200 - a decrease of the compressive strength after 200 freeze-thaw cycles was in the range from 4 to 12%. The lowest reduction of strength was observed for concrete with CEM I, w/c=0.34 and proper air entrainment. The properly air-entrained concrete layer with exposed aggregate, which was cured with a curing agent with closure capacity > 85%, was characterized by a very good resistance to surface scaling - the mass of scales m56 was equal to 0.10-0.12 kg/m2, irrespective of the type of cement and w/c ratio. However, there was a significant increase in the water absorption rate, surface scaling and chloride permeability, which caused with inadequate curing

air entrained concrete, curing, durability, exposed aggregate pavement, frost resistance, road pavement, permeability, scaling resistance

In this paper, the evolutionary computation procedures for identifying thermophysical properties in hardening massive concrete structures are presented. The heat of cement hydration, thermal conductivity and specific heat are determined for the purpose of modeling temperature evolution in massive concrete elements. Knowledge about temperature fields is very important due to their link with undesirable thermal stresses that can cause a weakening of structures because of thermal cracking. The proposed method is based on point temperature measurements in a cylindrical mould and the numerical solution of the inverse heat transfer problem by means of the finite element method and evolutionary computation

thermal properties of concrete, inverse heat transfer problem, early age concrete, evolutionary algorithm, FEM

Considering the long-time durability of concrete in road infrastructure it is important to control the threat of expansive reaction between sodium and potassium hydroxides in the pore solution and the reactive minerals present in the aggregate. Petrographic analysis is the basis for the qualification of aggregates to appropriate classes of reactivity according to ASTM C1778 and RILEM recommendations. This paper presents the results of petrographic analyses of thin sections made from twenty different domestic aggregates. The tested crushed aggregates were obtained from bedrock and glacial deposits. The evaluation of the mineral composition of aggregates included identification of deleterious components and determination of the content of reactive forms of silica. This enabled preliminary classification of aggregate in one of the three classes of reactivity according to RILEM. Obtained results provide an initial assessment of potential reactivity of aggregates and can assist in making decisions to undertake further accelerated or long-term laboratory testing or to modify the concrete mix design.

aggregate, alkali-aggregate reaction (AAR), petrographic analysis, reactive minerals, thin sections

Przedstawiono wyniki analizy petrograficznej 20 kruszyw łamanych z rożnych regionów Polski, przeprowadzonej na cienkich szlifach analizowanych pod mikroskopem w świetle przechodzącym. Próbki kruszyw grubych frakcji do 16 mm pochodziły ze skał litych oraz ze złóż polodowcowych z zakładów produkcji kruszyw, łamanych stosowanych do betonu. Ocenę składu mineralnego kruszyw, mającą na celu rozpoznanie składników szkodliwych, przeprowadzono z uwagi na zawartość reaktywnych minerałów krzemionkowych, m.in. opalu, krystobalitu, trydymitu, chalcedonu, wielkość kryształów (skryto- i mikrokrystaliczny kwarc) oraz kwarcu w stanie naprężeń. Zastosowanie metody petrograficznej na cienkich szlifach pozwoliło na wstępną kwalifikację do kategorii potencjalnie reaktywnej lub reaktywnej. Uzyskane wyniki badań stanowią wstępną informację o przydatności kruszyw jako składników betonu bądź o skierowaniu ich do dalszych szczegółowych badań lub ich odrzucenia

analiza petrograficzna, kruszywo, minerały reaktywne, reakcja alkaliczna kruszywa (AAR)

W artykule opisano podstawowe wyniki uzyskane w trakcie realizacji projektu badawczego „Trwałość i skuteczność betonowych osłon przed promieniowaniem jonizującym w obiektach energetyki jądrowej” [1]. Przedstawiono też wytyczne techniczne i kryteria oceny betonu osłonowego. Uzyskane wyniki mogą stanowić podstawę dalszych prac przy projektowaniu obiektów elektrowni jądrowych, składowisk materiałów radioaktywnych i innych miejsc powstawania, stosowania lub przechowywania materiałów wytwarzających promieniowanie jonizujące. Artykuł obejmuje zagadnienia związane z wymaganą skutecznością betonowych konstrukcji osłonowych przez zapewnienie bezpieczeństwa personelu i otoczenia przed oddziaływaniem promieniowania jonizującego. Rozpatrzono również trwałość osłon betonowych, tzn. zachowanie właściwości mechanicznych i nieprzepuszczalności w okresie przewidzianej eksploatacji pod wpływem przewidywanych oddziaływań zewnętrznych i procesów starzenia, a także przy podwyższonej temperaturze i promieniowaniu jonizującym. Artykuł nie obejmuje zagadnień integralności osłon pod obciążeniami wyjątkowymi, spowodowanymi awarią reaktora, uderzeniem samolotu, działaniami terrorystycznymi itp.

The influence of blended cements containing calcareous fly ash (W) on the strength and permeability of air entrained concrete was studied. Moderately active calcareous fly ash of CaO content of 26% and loss on ignition of 2%, obtained from lignite fired power station in Poland, was selected. Ternary cement compositions including siliceous fly ash (V) and ground granulated blast furnace slag (S) were also studied. Air void analysis in hardened concrete was used to evaluate the effectiveness of air entraining process. Pore size distribution was characterized by mercury intrusion porosimetry (MIP). The presence of calcareous fly ash in cement resulted in a moderate increase in the compressive strength of concrete and an increase of the category of resistance to chloride ion migration. Test results revealed a linear relationship between the capillary porosity measured by MIP and the chloride migration coefficient (Dnssm). The permeability was lower for increased clinker replacement level which was due to formation of smaller diameters of the capillary pores.

Air entrained concrete, Air void characteristics, Calcareous fly ash, Chloride ion migration, Multicomponent cements, Pore size distribution, Strength

The objective of this paper is to examine the possible use of new blended cements containing calcareous fly ash in structural concrete, potentially adequate for structural elements of nuclear power plants. The investigation included five new cements made with different contents of non-clinker constituents: calcareous fly ash, siliceous fly ash, ground granulated blastfurnace slag, and a reference cement—ordinary Portland cement. The influence of innovative cements on the resistance of concrete to chloride and carbonation exposure was studied. Additionally, an evaluation of the microstructure was performed using optical microscopy on concrete thin sections. Test results revealed a substantial improvement of the resistance to chloride ion penetration into concrete containing blended cements. The resistance was higher for increased clinker replacement levels and increased with curing time. However, concrete made with blended cements exhibited higher depth of carbonation than the Portland cement concrete, except the Portland-fly ash cement with 14.3% of calcareous fly ash. The thin sections analysis confirmed the values of the carbonation depth obtained from the phenolphthalein test. Test results indicate the possible range of application for new cements containing calcareous fly ash.

blended cements, calcareous fly ash, chloride migration, carbonation, durability, nuclear shielding concrete, thin sections

Alkali-silica reaction (ASR) is considered as a potential aging-related degradation phenomenon that might impair the durability of concrete in nuclear containments. The objective of this paper is the application of digital analysis of microscopic images to identify the content and size of quartz grains in heavy mineral aggregates. The range of investigation covered magnetite and hematite aggregates, known as good absorbers of gamma radiation. Image acquisition was performed using thin sections observed in transmitted cross-polarized light with λ plate. Image processing, consisting of identification of ferrum oxide and epoxy resin, and the subsequent application of a set of filtering operations resulted in an adequate image reduction allowing the grain size analysis. Quartz grains were classified according to their mean diameter so as to identify the reactive range. Accelerated mortar bar tests were performed to evaluate the ASR potential of the aggregates. The SiO2 content in the heavyweight aggregates determined using the image analysis of thin sections was similar to XRF test result. The content of reactive quartz hematite was 2.7%, suggesting that it would be prone to ASR. The expansion test, according to ASTM C1260, confirmed the prediction obtained using the digital image analysis.

alkali-silica reaction, grain size, heavyweight aggregate, image analysis, radiation shielding concrete, reactive aggregate, quartz

The results of studies of concretes from the special cements, destined to the production of shields against the radiation. The study included Portland cement, Portland fly ash cement, and cements with different content of granulated blastfurnace slag. The application of special cements decreased the possibility of ASR occurrence. CEM I 42.5N LH/SR3/NA and CEM III/A 42.5N LH/HSR/NA usage in heavy concrete of gravity in the range of 3200-3600 kg/m3, the compressive strength was in the range of 45-62 MPa and 62-81 MPa after 28 and 90 days, respectively. The comparison of the effect of CEM III/A 42,5N LH/HSR/NA usage instead of CEM I 42,5N LH/SR3/NA for heavy concrete production the systematic decrease of the rate of water absorption, decrease of coeffi cient of chloride ions diffusion, but increased the carbonation rate, was shown.

special cements, concrete shields

We present a review of freeze-thaw durability requirements laid down in both European standards and in the national specifications in relation to concrete for road structures. The principles of material selection for concrete mix are presented. We discuss local variations in the severity of the winter season and the extent of frost action in the components of road structures. The characteristic parameters of the test procedure for direct assessment of the resistance of concrete to internal damage are analysed, with particular attention paid to the specimen cooling rate. The temperature distribution in specimens was determined in standard freeze-thaw resistance tests carried out at two accredited laboratories. We discuss the criteria used in indirect assessment of freeze-thaw durability of air-entrained concrete on the basis of air void characteristics. Based on the determined temperature distribution in concrete specimens we postulate an improvement of the standard test procedure to clearly specify the cooling rate. It would be beneficial to distinguish frost impact zones depending on the severity of action of frost and de-icing salts on concrete in road structures.

air void characteristics, concrete, cooling rate, durability, internal frost resistance, mix design, performance specification, test methods

Przedstawiono wyniki badań podciągania kapilarnego (PK), porowatości dostępnej dla wody (E) oraz współczynnika migracji jonów chlorkowych w stanie nieustalonym (Dnssm). Zakres badań obejmował betony z kruszywem magnetytowym, barytowym, serpentynitowym oraz kruszywem referencyjnym w postaci grysu amfibolitowego, które wcześniej poddane zostały selektywnemu kruszeniu i przesiewaniu, tak by zapewnić jednakowe krzywe uziarnienia/stosy okruchowe. Prze analizowano wpływ mikrostruktury porów wyznaczonej za pomocą porozymetrii rtęciowej z odpornością na wnikanie jonów i cieczy w matrycę cementową. Z badań wynika, że betony z kruszywami specjalnymi osiągają wskaźniki przepuszczalności porównywalne lub nieco gorsze niż próbki referencyjne. Nie zaobserwowano systematycznego wpływu porowatości kapilarnej na wyniki badań przepuszczalności.

podciąganie kapilarne, migracja jonów chlorkowych, kruszywo magnetytowe, kruszywo barytowe, kruszywo serpentynitowe, porowatość

W artykule przedstawiono wyniki badań parametrów termicznych procesu twardnienia mieszanek betonowych, z których dwie wykonano z wykorzystaniem kruszyw stosowanych w produkcji betonów osłonowych (kruszywo magnetytowe oraz serpentynitowe), a trzecią, referencyjną, z wykorzystaniem kruszywa amfibolitowego. Na podstawie analizy dokonanych pomiarów temperatury wyznaczono parametry procesu twardnienia betonu (m.in. maksymalny przyrost temperatury, maksymalny gradient i in.). Jednocześnie rozwiązując numerycznie tzw. zagadnie-nie odwrotne wyznaczono parametry cieplne betonu w trakcie pierwszych 72 godzin twardnienia. Tą samą metodą wyznaczono również wartości funkcji źródła ciepła, a następnie na jej podstawie oszacowano ilość ciepła wydzieloną w procesie hydratacji cementu. Uzyskano dobrą jakościową zgodność postaci funkcji źródła ciepła oraz wykresów zmian temperatury w mieszankach. W toku analiz uzyskanych wyników wyraźnie zaznaczył się wpływ zróżnicowania parametrów cieplnych zastosowanych kruszyw. W przypadku mieszanki z kruszywem serpentynitowym dały się także zauważyć istotne różnice w przebiegu przyrostu temperatury (opóźnienie) w stosunku do pozostałych mieszanek

młody beton, beton osłonowy, ciepło hydratacji, ciepło właściwe, współczynnik przewodzenia ciepła

Celem Projektu ASR-RID jest opracowanie wytycznych technicznych projektowania betonów o dużej trwałości, ze szczególnym uwzględnieniem zabezpieczenia przed wystąpieniem uszkodzeń spowodowanych reakcją AAR, tj. między NaOH i KOH, a reaktywnymi minerałami w kruszywie. Przedmiotem badań są kruszywa ze złóż w rożnych regionach Polski. Reaktywność alkaliczna kruszyw jest oznaczana i oceniana przy wykorzystaniu komplementarnych metod, stosowanych w systemach oceny reaktywności kruszyw w wiodących technologicznie krajach. Projekt zakłada opra-cowanie kryteriów oceny reaktywności kruszyw, z możliwością wykorzystania w systemie kontroli produkcji i ich do-staw na potrzeby wytwarzania betonów drogowych. Ocena reaktywności zostanie zweryfikowana na podstawie eks-pansji betonu w warunkach eksploatacyjnych.

reakcja alkalia-kruszywo, beton, trwałość, nawierzchnie drogowe, mosty,, metoda petrograficzna, przyspieszona metoda badania ekspansji, testy funkcjonalne

The use of recycled aggregates in concrete is on the rise, driven by economic and environmental concerns. However, most of the existing models to predict the value of elastic modulus of concrete were developed for virgin aggregates and, as a result, they may often be inaccurate when applied to concrete made with recycled aggregate. In this study, the M5′ model tree algorithm was used to predict the elastic modulus of recycled aggregate concrete. The main advantages of the model tree algorithms are: (a) they output relatively simple mathematical models (formulas) and (b) are more convenient to develop and employ compared with other soft computing methods. To develop the model tree presented in this paper, over 450 data records were collected from internationally published literature. Error measures were used to compare the performance of the M5′ algorithm output to the output from other existing models. The results showed that the model developed using the M5′ algorithm has accuracy over 80 percent, which is well above the accuracy the other models.

M5′ model tree, Modulus of elasticity, Recycled aggregate, Concrete

The aim of the study was to generate rules for the prediction of the chloride resistance of concrete modified with high calcium fly ash using machine learning methods. The rapid chloride permeability test, according to the Nordtest Method Build 492, was used for determining the chloride ions’ penetration in concrete containing high calcium fly ash (HCFA) for partial replacement of Portland cement. The results of the performed tests were used as the training set to generate rules describing the relation between material composition and the chloride resistance. Multiple methods for rule generation were applied and compared. The rules generated by algorithm J48 from the Weka workbench provided the means for adequate classification of plain concretes and concretes modified with high calcium fly ash as materials of good, acceptable or unacceptable resistance to chloride penetration.

chloride penetration, concrete, durability, high calcium fly ash, machine learning

Konsorcjum„Atomshield” realizuje projekt badań stosowanych, dotyczących trwałości i skuteczności betonowych osłon przed promieniowaniem w elektrowniach jądrowych. Wpracy przedstawiono genezę problematyki oraz wybrane rezultaty przeprowadzonych badań. Kryteria oceny długotrwałej funkcjonalności betonu, adekwatne do wysokiej niezawodności reaktorów generacji III+, obejmują m.in. nieprzepuszczalność betonu wobec mediów ciekłych i gazowych, wskaźniki ryzyka wystąpienia wewnętrznych zjawisk ekspansywnych i wczesnych spękań betonu. Omówiono wdrożenie opracowanej technologii betonu z kruszywem magnetytowym do budowy masywnych bunkrów akceleratorów wysokoenergetycznych.

beton osłonowy, elektrownia jądrowa, projektowanie betonu, trwałość

In the paper the qualitative and quantitative methods of concrete air entrainment were presented, not only these which are in standards but also beyond them. From the last ones the foam index, foam stability and the method applying buoyancy rule of particles migration were described and their drawbacks as well as good points are given. Detailed discussion is devoted to microscopic method of pore structure determination and the drawback of standard lack is underlined. Also the Danish, German and Canadian standards are discussed, the last one especially in the case of road construction.

air entrainment, air voids, distribution, image analysis, microscopy, microstructure, test method

The recent mechanistic-empirical pavement design guide (MEPDG) put more emphasis on the effects of thermal curling stresses on rigid pavement analysis and design. Mix design of concrete has significant influence on its thermal properties such as thermal conductivity, coefficient of thermal expansion, and specific heat. Aggregate type and content significantly alter the thermal properties of concrete incorporating them. The moisture state of the concrete increases its specific heat and thermal conductivity. A review of the effect of temperature of fresh concrete on early age properties is also presented. The performance of rigid pavements exposed to seasonal and daily fluctuations in temperature is discussed. Airfield concrete pavements which are subjected to jet engine exhausts experience heat cycles micro-cracking, coarsening of microstructure and loss of compressive and flexural strength. These effects are mostly the result of the dehydration and decomposition of paste matrix in concrete. Heat cycles result in concrete deterioration similar in appearance to freezing and thawing deterioration.

coefficient of thermal expansion, temperature gradient, thermal conductivity, thermal properties, concrete pavement

As a measure to avoid thermally induced cracking in massive concrete, mineral admixtures are often added as a substitute for a certain portion of cement. This paper presents the results of testing in course of which the temperature was measured during hardening of concrete mixtures produced with addition of calcareous fly ash obtained from the Power Station in Bełchatów, Poland. The investigation covered 76 concrete mixtures produced with three different aggregates and diverse binder content. In the experimental part of the research, the thermal parameters of hardening concrete were determined with a specially developed method in which the mixture was placed in a one-dimensional mould which allowed for unrestrained flow of heat in one direction. The results of testing were used to assess the influence of the respective ingredients, in particular calcareous fly ash, on the rate of rise of the fresh concrete temperature, on the time of occurrence of the maximum temperature and on the temperature gradients. Finally, a formula for calculating the specific heat of hydration depending on the mixture composition was proposed.

high calcium fly ash, fresh concrete temperature, heat of hydration, massive concrete, multicomponent cement, temperature gradient

The paper presents the investigation of concrete resistance to penetration by liquid and gaseous environmental media. Calcareous fly ash obtained from Bełchatów Power Station was used as concrete additive. In the mix design a certain portion of binder (15% and 30%) was substituted with calcareous fly ash assuming the efficiency factors of 0.7 or 1.0. The tested parameters included the air permeability coefficient measured with Torrent method, the depth of water penetration under pressure and the coefficient of chloride ions migration measured with the rapid chloride migration test. It was established that the addition of calcareous fly ash resulted in the desired reduction of the value of a chloride migration coefficient while the effect on the permeability of water and air was similar to the effect it had on the compressive strength of concrete.

air permeability, calcareous fly ash, chloride migration, compressive strength, fly ash processing, Torrent method, water permeability

The investigation of concrete microstructure and phase composition was performed on concrete specimens produced with and without calcareous fly ash obtained from Bełchatów Power Station. The used calcareous fly ash (designated “W”) was either unprocessed or ground to assumed specific surface and added to concrete mix to substitute 30% of the binder by weight. The following testing methods were used in this research: scanning electron microscopy, differential thermal analysis (DTA) and multiple microindentation. The characteristic features of the investigated microstructures are discussed and the effect of calcareous fly ash on the content of non-evaporable water and portlandite in cement matrix is analysed. The results of microindentation and compressive strength testing were used as the basis for evaluation of the efficiency of calcareous fly ash added to concrete mix.

calcareous fly ash, microindentation, microstructure, non-evaporable water, phase composition, portlandite, strength

The paper presents results of the investigation of the air void characteristics and the resistance to cyclic freezing and thawing of air-entrained concrete containing calcareous fly ash. The frost resistance was tested also under the presence of de-icing salts to check the resistance to frost-salt scaling and without de-icing salts. The range of investigation included air entrained concrete mixes with the specified water-binder ratio of w/b=0.45 with addition of calcareous fly ash or made using blended cements with calcareous fly ash (W), and also siliceous fly ash (V) and ground granulated blast-furnace slag (S). The coarse aggregates used were crushed granodiorite and crushed limestone. The air-void system parameters were determined by microscopic image analysis and the effect of addition of calcareous fly ash was assessed. The effect of concrete age and presence of fly ash W on the strength and freeze-thaw resistance was also studied. The tests have shown that the use of calcareous fly ash as one of the main constituents of blended cements does not affect the frost salt scaling resistance nor the resistance to internal frost damage provided that the air void system is adequate.

air-void system parameters, blended cements, calcareous fly ash, freeze-thaw resistance, scaling resistance

Przedstawiono wyniki badań wytrzymałości na ściskanie, odporności na wnikanie chlorków oraz odporności na powierzchniowe łuszczenie w obecności soli odladzających betonów napowietrzonych z popiołem lotnym wapiennym (W). Próbki betonu dojrzewały w odmiennych warunkach wilgotnościowych. Zakres badań obejmował betony napowietrzone o współczynniku w/c=0,45 wykonane z cementów portlandzkich wieloskładnikowych z dodatkiem popiołu W oraz z dodatkami popiołu lotnego krzemionkowego V i mielonego granulowanego żużla wielkopiecowego S. Próbki dojrzewały przez 28 i 90 dni, z czego połowa w wodzie, natomiast druga połowa po 3 dniowej pielęgnacji w powietrzu w wilgotności RH=40%. Charakterystyka porów powietrznych w stwardniałym betonie została oznaczona metodą mikroskopowej analizy obrazu. Z badań wynika, że przy zbliżonych parametrach charakterystyki porów powietrznych zmiana warunków pielęgnacji próbek obniża w znaczący sposób trwałość betonu. Największy wpływ zmiennych warunków i czasów dojrzewania zaobserwowano w odniesieniu do odporności betonu na agresję mrozu i środków odladzających.

charakterystyka porów, napowietrzenie, penetracja chlorków, popiól lotny wapienny, powierzchniowe złuszczenie

The objective of this investigation was to develop rules for automatic assessment of concrete quality by using selected artificial intelligence methods based on machine learning. The range of tested materials included concrete containing nonstandard waste material—the solid residue from coal combustion in circulating fluidized bed combustion boilers (CFBC ash) used as an additive. Performed experimental tests on the surface scaling resistance provided data for learning and verification of rules discovered by machine learning techniques. It has been found that machine learning is a tool that can be applied to classify concrete durability. The rules generated by computer programs AQ21 and WEKA by using the J48 algorithm provided a means for adequate categorization of plain concrete and concrete modified with CFBC fly ash as materials resistant or not resistant to the surface scaling.

Machine learning, Automatic classification rules, Database, Concrete durability, Scaling resistance, Circulated fluidized bed combustion fly ash (CFBC fly ash)

The objective of this investigation was to develop rules for automatic categorization of concrete quality using selected artificial intelligence methods based on machine learning. The range of tested materials included concrete containing a new waste material - solid residue from coal combustion in fluidized bed boilers (CFBC fly ash) used as additive. The rapid chloride permeability test - Nordtest Method BUILD 492 method was used for determining chloride ions penetration in concrete. Performed experimental tests on obtained chloride migration provided data for learning and testing of rules discovered by machine learning techniques. It has been found that machine learning is a tool which can be applied to determine concrete durability. The rules generated by computer programs AQ21 and WEKA using J48 algorithm provided means for adequate categorization of plain concrete and concrete modified with CFBC fly ash as materials of good and acceptable resistance to chloride penetration.

concrete durability, chloride ions migration, circulated fluidized bed combustion fly ash (cfbc fly ash), machine learning, classification rules, database

Concrete manhole covers of underground cable networks, placed into pavements of roadways and footways, are often subjected to premature damage posing a threat to traffic safety. That is why the investigation was undertaken to increase the durability of precast concrete covers. New concrete mixtures for precast elements as well as the structure of elements (the type of a chassis, the number and arrangement of reinforcement bars) were designed. Experimental research into the load bearing capacity of concrete elements manufactured in multiple precast plants according to the assumed mix design was carried out. The impact of the type of cement, chemical admixtures and fibre reinforcement on the load capacity of precast concrete elements was assessed. The high effectiveness of fibre reinforcement enhancing the load bearing capacity of concrete covers was found.

concrete, concrete precast elements, fibre-concrete, load capacity, manhole covers

The paper presents the procedure of determining the thermophysical properties of concrete: heat of hardening, thermal conductivity and specific heat, which is based on point temperature measurements in a cylindrical mold and the numerical solution of the inverse heat transfer problem. The procedure was tested on concrete materials made with high-calcium fly ashes. The obtained results show good agreement with the real values of individual parameters and can be used to determine the temperature field in the object of any complex shape.

calcerous fly ash, heat equation, inverse problem, massive concrete, thermal gradient

Od kilku lat jednym z najważniejszych problemów do rozwiązania, na które oczekuje przemysł mineralnych materiałów wiążących, jest znaczące ograniczenie emisji do atmosfery dwutlenku węgla. Służące temu celowi działania obejmują między innymi zarówno działania polegające na zastąpieniu cementów bazujących na klinkierze portlandzkim innymi rodzajami spoiw mineralnych o zbliżonych właściwościach użytkowych, jak też ograniczanie zawartości klinkieru portlandzkiego w cementach powszechnego użytku i zastępowanie go innymi składnikami aktywnym w układach cenent-woda. Celem artykułu jest przedstawienie obydwu rodzajów działań podejmowanych w okresie ostatnich dwóch lat, a zwłaszcza zaprezentowanie szeroko reklamowanej i nagradzanej technologii, której produktem finalnym są magnezjowe materiały wiążące nowej generacji.

Spoiwo magnezjowe, redukcje emisji dwutlenku węgla, cementy wieloskładnikowe, skład ziarnowy cementu

Celem przeprowadzonych badań była ocena przepuszczalności betonu zawierającego popiół lotny wapienny pochodzący ze spalania węgla brunatnego, w stanie surowym i po dodatkowym domieleniu. W badaniach skoncentrowano się na określeniu wpływu ilości popiołu jako dodatku do betonu na wnikanie mediów agresywnych. Określono podstawowe właściwości mieszanki betonowej oraz wytrzymałość na ściskanie. Oznaczono współczynnik migracji jonów chlorkowych przy nieustalonym ich przepływie, głębokość penetracji wody pod ciśnieniem oraz współczynnik gazoprzepuszczalności betonu. Mikrostrukturę badanych betonów przeanalizowano na cienkich płytkach w mikroskopie polaryzacyjnym do światła przechodzącego. Stwierdzono, że zastąpienie cementu przez dodatek popiołów lotnych wapiennych do betonu w ilości 15% lub 30% przy w / s =0,55 powoduje poprawę ich wodo- i gazoszczelności, z tą jednak różnicą, że do zmniejszenia gazoprzepuszczalności betonu odpowiedniejsze jest stosowanie popiołów domielonych. Niższe wartości współczynnika migracji jonów chlorkowych otrzymano w betonach zawierających popiół lotny wapienny, wzrost w / s zwiększył przenikalność jonów chlorkowych. Analiza obrazów na cienkich szlifach betonowych wykazała, że w miarę wzrostu zawartości popiołu w betonie wzrasta również ilość niespalonych cząstek węgla w matrycy, których wielkość jest zależna od czasu mielenia popiołu

gazoprzepuszczalność, migracja chlorków, mikrostruktura, popiół lotny wapienny, wodoprzepuszczalność

W artykule podjęto temat jakości betonu w kontekście powstawania spękań. Omówiono sytuacje sporne dotyczące interpretacji wyników badań kontrolnych jakości betonu. Stwierdzono, że przy projektowaniu składu betonu przeznaczonego na konstrukcje inżynierskie potrzebna jest ocena jego podatności na powstawanie rys przy rozmaitych oddziaływaniach mechanicznych i środowiskowych. Nie można bowiem ograniczać się do projektowania betonu wysokiej trwałości jedynie „między rysami”. Przydatne są tu koncepcje i metody mechaniki pękania rozwijane od ponad 30 lat w odniesieniu do betonu.

beton, jakość, mrozoodporność, spękania, właściwości mechaniczne

The objective of the presented investigation was to design the computer-aided procedure to assist the concrete component identification using microhardness testing method and the experimental verification of its efficiency by examination of concrete specimens. Two algorithms of analysis of Acoustic Emission (AE) signal evoked during microindentation were applied. AE signal processing was made by means of computer programs enabling for integrated processing of registered data. Data sets created during microindentation processes were analysed in order to distinguish indents in cement matrix, in aggregate grains and in other areas. The most efficient of the proposed selective criterions, used within a computer software based on wavelet filtering of the recorded AE signal, enabled for successive recognition of concrete components with the efficiency of 76 % within the tested population.

acoustic emission, microhardness, phase recognition, testing method, wavelet filtering

Przedstawiono wyniki pracy badawczej „Analiza wymagań i opracowanie kryteriów bezpieczeństwa użytkowania zwieńczeń studni kanalizacji kablowej wykonywanych w nawierzchniach dróg i ciągów pieszych” realizowanej w Instytucie Badawczym Dróg i Mostów we współpracy z Zakładem Doświadczalnym Budownictwa Łączności, IPPT PAN oraz Politechniką Warszawską. Przeprowadzono badania doświadczalne właściwości mechanicznych i trwałości betonu przeznaczonego do wykonania prefabrykatów. Wykonano badania nośności całych prefabrykatów, wykonanych w różnych zakładach produkcyjnych na podstawie opracowanych recept betonu. Przeanalizowano wpływ rodzaju cementu, domieszek chemicznych i zbrojenia rozproszonego na nośność prefabrykatów betonowych oraz na odporność betonu na oddziaływania klimatyczne i eksploatacyjne.

konstrukcja pokryw, nośność, skład betonu, trwałość, właściwości mechaniczne

The experimental investigation on the frost-salt scaling resistance of air-entrained concrete containing CEM II/B-S 42.5N and CEM III/A 42.5N-HSR/NA slag-blended cements was performed. The air void system in concrete was evaluated in fresh concrete using AVA and in hardened concrete using an automated image analysis procedure. The mass of scaled material was increased for an increased slag content, in spite of increased compressive strength and flexural strength, decreased water absorption and decreased depth of water penetration of concrete. Increasing slag content resulted in a decrease of the total volume of air in hardened concrete and in a corruption of the air void system exhibited by a decrease of micropores content. The increase of mass of scaled material was proportional to the increase of the spacing factor of air voids, except for CEM III/A cement concrete exhibiting accelerated scaling.

Air-entrained concrete, Air voids, Frost-salt scaling, Image analysis, Slag-blended cement

The possibility for using coal combustion by-products in concrete exposed to frost-salt aggression was investigated. The research was aimed to assess an influence addition of circulating fluidized bed combustion (CFBC) fly ash on frost-salt scaling of air-entrained concrete. For evaluation of the resistance of concrete to frost salt scaling the test called ‘‘depth sensing indentation’’ (DSI) was applied. The DSI test method was implemented on a universal testing frame using a standard Vickers indenter. Experimental tests were performed on cement paste specimens and concrete specimens designed with partial replacement of cement with coal combustion by-products. The mass of scaled material in standard frost salt scaling resistance tests on concrete was inversely proportional to the Vickers hardness of the paste containing CFBC fly ash; the best-fit arithmetic relationship is provided.

Air entrained concrete, CFBC fly ash, Frost scaling resistance, Hardened cement paste, Microhardness

Przedmiotem artykułu są prefabrykowane betonowe pokrywy studni kanalizacji kablowej, stosowane w ciągach dróg dla pieszych i pojazdów. Celem podjętej pracy było rozpoznanie stanu technicznego betonowych pokryw studni kanalizacji kablowej na podstawie obserwacji prefabrykatów zabudowanych w ciągach drogowych oraz na podstawie wyrywkowych analiz jakości betonu w pokrywach. Stwierdzono, że przeważająca część wbudowanych pokryw ma uszkodzenia i wady produkcyjne, ujawniające się już po jednym roku eksploatacji. Stwierdzono też częste przekroczenie tolerancji wymiarowych pokryw, a także ewidentne błędy instalacji pokryw i zwieńczeń w jezdni, wystających nawet do 60 mm powyżej poziomu jezdni. Na podstawie przeprowadzonych analiz jakości betonu w pokrywach stwierdzono duży rozrzut wytrzymałości betonu na ściskanie, przy czym blisko 15 % próbek wykazało wytrzymałość poniżej 25 MPa wymaganej dla najniższej klasy zwieńczeń A-15.

diagnostyka, nośność, pokrywy studni, uszkodzenia, wytrzymałość

The increased use of advanced coalburning technologies for power generation, such as circulating fluidized bed combustion (CFBC), results in new waste products. The potential for using CFBC fly ash in air-entrained concrete was investigated in order to assess the influence of CFBC fly ash on the microstructure of air voids in hardened concrete. A special specimen surface preparation technique for contrasting the image and enabling measurements of air voids size and distribution using an automated image analysis procedure was used. The microstructure of air voids was evaluated on the basis of the total air content, the spacing factor, and the specific surface of air voids. It was found that a satisfactory air void system in concrete could be produced when using CFBC fly ash for partial replacement of cement. The air-void system was characterized by a decreased specific surface of voids and an increased spacing factor

CFBC fly ash, Image analysis, Microstructure, Air-entrained concrete

The phase composition of the cement paste phase of concrete containing fly ash from circulating fluidized bed combustion (CFBC) was studied. The motivation was to broaden the knowledge concerning the microstructure and the durability of concrete containing new by-products from the power industry. Several air-entrained concrete mixes were designed with constant water to binder ratio and with substitution of a part of the cement by CFBC fly ash (20%, 30% or 40% by weight). X-ray diffraction tests and thermal analysis (DTG, DTA and TG) were performed on cement paste specimens taken from concrete either stored in water at 18◦C or subjected to aggressive freeze-thaw cyclic action. The evaluation of the phase composition as a function of CFBC fly ash content revealed significant changes inportlandite content and only slight changes in the content of ettringite. The cyclic freeze-thaw exposure did not have any significant influence on the phase composition of concrete with and without the CFBC fly ash.

air-entrained concrete, fluidized bed fly ash, freeze-thaw durability, waste management

Przeprowadzono badania doświadczalne wpływu zawartości makrowłókien syntetycznych na właściwości mechaniczne betonu stwardniałego w zakresie odpowiadającym potencjalnym zastosowaniom w płytach nośnych podłóg przemysłowych wylewanych na podłożu gruntowym. Stwierdzono jakościowe podobieństwo charakterystyki mechanicznej fibrobetonu z włóknami stalowymi i z makrowłóknami syntetycznymi, tzn. ciągliwość materiału ujawniającą się jako zdolność do przenoszenia znaczących obciążeń rozciągających po powstaniu zarysowań oraz radykalny wzrost odporności na pękanie w porównaniu z betonem bez włókien. Wytrzymałość równoważna na zginanie fibrobetonu z makrowłóknami syntetycznymi wynosiła średnio 1,30 MPa, 1,88 MPa i 2,18 MPa, odpowiednio przy zastosowaniu włókien w ilości 2, 3 i 4 kg/m3. Wskaźnik wytrzymałości równoważnej na zginanie wzrastał ze wzrostem zawartości włókien i wynosił średnio od 0,34 do 0,56. Stosowanie wysokich zawartości ≥ 4 kg/m3 makrowłókien syntetycznych w betonie wymaga odpowiednio silnego upłynnienia mieszanki przy użyciu domieszek chemicznych.

badania doświadczalne, fibrobeton, makrowłókna syntetyczne, odporność na pękanie, wytrzymałość równoważna na zginanie

Przeprowadzono badania rozmieszczenia porów powietrznych w betonie napowietrzonym, zawierającym popioły lotne ze spalania węgla kamiennego w kotłach fluidalnych. Dodatek popiołów lotnych z kotłów fluidalnych stosowano jako zamiennik części cementu CEM I w mieszance betonowej. Na podstawie badania zawartości powietrza w mieszance metodą ciśnieniową stwierdzono, że zastosowanie popiołów lotnych z kotłów fluidalnych do betonu wymaga zwiększenia ilości domieszki napowietrzającej: stwierdzony wzrost był proporcjonalny do wzrostu zawartości dodatku. Przy wykorzystaniu automatycznej analizy obrazu na próbkach stwardniałego betonu określono rozmieszczenie i rozkład wielkości porów. Przy wzrastającej zawartości dodatku popiołów lotnych z kotłów fluidalnych stwierdzono zmiany mikrostruktury porów, odzwierciedlone wzrostem wskaźnika rozmieszczenia porów powietrznych oraz spadkiem powierzchni właściwej porów.

automatyczna analizy obrazu, domieszka napowietrzająca, charakterystyka porów, mikrostruktura, popiół lotny fluidalny, powierzchnia właściwa porów, wskaźnika rozmieszczenia porów

Główne tendencje kształtujące rozwój betonu w ostatnich latach zostały przedstawione w referacie L.Czarneckiego i W.Kurdowskiego, natomiast nieco wcześniej, w latach 2003-2003, na łamach Kwartalnika „Budownictwo-Architektura-Technologie” miała miejsce dyskusja na temat przyszłości betonu. Omówione zostały m.in. zewnętrzne uwarunkowania rozwoju betonu w skali globalnej; wymieniono tu masowe zużycie surowców naturalnych i energii, znaczący udział w globalnej emisji CO2 oraz wzrost populacji ludności świata. Na podstawie tzw. uogólnionej krzywej rozwoju zilustrowano postęp jakościowy, reprezentowany wzrostem wytrzymałości na ściskanie, jak też ilościowy, mierzony wzrostem masy betonu produkowanego na świecie. Stwierdzono też, że beton przyszłości będzie materiałem „opartym na wiedzy” i zaproponowano, aby wiedzę tę rozwijać. Celem niniejszego referatu jest uzupełnienie takiego przeglądu tendencji rozwojowych o spostrzeżenia na podstawie doświadczeń i wyników działania europejskich sieci naukowych oraz niektórych projektów badawczych fundowanych przez UE.

analiza cyklu życia, oddziaływania środowiskowe, projektowanie na trwałość, reologia mieszanki, technologia betonu, zbrojenie rozproszone

Główne tendencje kształtujące rozwój betonu w ostatnich latach zostały przedstawione w referacie L.Czarneckiego i W.Kurdowskiego, natomiast nieco wcześniej na łamach Kwartalnika „Budownictwo-Architektura-Technologie” miała miejsce dyskusja na temat przyszłości betonu. Omówione zostały m.in. zewnętrzne uwarunkowania rozwoju betonu w skali globalnej; wymieniono tu masowe zużycie surowców naturalnych i energii, znaczący udział w globalnej emisji CO2 oraz wzrost populacji ludności świata. Na podstawie tzw. uogólnionej krzywej rozwoju zilustrowano postęp jakościowy, reprezentowany wzrostem wytrzymałości na ściskanie, jak też ilościowy, mierzony wzrostem masy betonu produkowanego na świecie. Stwierdzono też, że beton przyszłości będzie materiałem „opartym na wiedzy” i zaproponowano, aby wiedzę tę rozwijać. Celem niniejszego referatu jest uzupełnienie takiego przeglądu tendencji rozwojowych o spostrzeżenia na podstawie doświadczeń i wyników działania europejskich sieci naukowych oraz niektórych projektów badawczych fundowanych przez UE.

analiza cyklu życia, oddziaływania środowiskowe, projektowanie na trwałość, reologia mieszanki, zbrojenie rozproszone

Powstawanie rys w betonowych konstrukcjach inżynierskich może powodować obniżenie sztywności i wytrzymałości elementów, zmniejszenie szczelności betonu i niebezpieczeństwo korozji zbrojenia. W pracy przedstawiono laboratoryjny sposób diagnostyki rys w betonie metodą mikroskopową przy wykorzystaniu komputerowego analizatora obrazu. Opracowanie metody wykrywania i analizy rys obejmowało m.in. utworzenie laboratoryjnej procedury przygotowania próbek do obserwacji mikroskopowych, zdefiniowanie parametrów charakteryzujących wymiary i rozmieszczenie rys, opracowanie automatycznych algorytmów identyfikacji rys przy uwzględnieniu przekształceń morfologicznych i współczynników kształtu, wyznaczania stopnia orientacji rys oraz określania rozkładu ich szerokości. Poprawność działania metody diagnostycznej została pozytywnie zweryfikowana na próbkach betonu konstrukcyjnego poddanych cyklicznemu zamrażaniu i odmrażaniu oraz na próbkach fibrobetonu obciążanych do określonego poziomu siły ściskającej.

cyfrowa analiza obrazu, diagnostyka, metoda mikroskopowa, mikrostruktura, rysy

An automated method for crack identification and quantitative description of crack systems in concrete was developed in order to aid a service life assessment of concrete elements in structures. Flat polished specimens for crack analysis were impregnated with epoxy resin containing fluorescent dye. The examination of the crack system was performed in ultraviolet light using a stereomicroscope and an Image Pro Plus image analysis system on specimens cored out of several concrete structures. The laboratory tests were performed on cast specimens to establish correlations between water penetration and chloride diffusion and crack system parameters. The analysis of cracks in concrete cores taken from structures resulted in interesting conclusions based on the crack width distribution and crack localization with respect to steel reinforcement. The method was found very effective to support standard concrete diagnostics methods.

cracks, crack pattern, image analysis, concrete structures

Artykuł przedstawia krytyczny przegląd wymagań wytrzymałości betonu na rozciąganie przy zginaniu w nawierzchniach drogowych pod kątem technicznych możliwości ich spełnienia i sprawdzenia w nawierzchni, a także spójności z kryterium właściwej struktury porów powietrznych, niezbędnej w celu zapewnienia mrozoodporności. Liczne wyniki badań wskazują na istnienie liniowej relacji między wytrzymałością na rozciąganie przy zginaniu i wytrzymałością na ściskanie do potęgi 2/3 lub1/2. Rozrzut wyników badania wytrzymałości na rozciąganie przy zginaniu jest na ogół ok. dwa razy większy niż rozrzut wyników badania wytrzymałości na ściskanie; współczynnik zmienności sięga często 10-15%. W przypadku betonu klasy B 40 realnie osiągalna wartość fckt,fl wynosi około 4,5 MPa. Zarówno całkowita porowatość, ale także rozkład wielkości porów powietrznych mają istotny wpływ na wytrzymałość betonu. Procedury kontroli właściwości betonu powinny uwzględniać fakt, że wytrzymałość betonu i zawartość powietrza niezbędnego w celu zapewnienia mrozoodporności, są wymaganiami konfliktowymi. Jak stwierdzono, aktualne normy nie dość ściśle określają procedury pobierania elementów próbnych i przeprowadzenia badania. Jednoznaczna ocena wyników badania wytrzymałości wymaga nawiązania do współczesnych norm budowlanych i uściślenia kryteriów zgodności.

charakterystyka porów, kontrola jakości, kryteria zgodności, nawierzchnie drogowe, napowietrzenie, wytrzymałość na rozciąganie przy zginaniu

Przedstawiono porównanie wymagań normowych na skład i właściwości betonu w państwach europejskich o klimacie zbliżonym do klimatu Polski. Omówiono wymagania dotyczące napowietrzenia betonu w klasie ekspozycji XF1 – XF4.
Wykazano braki w krajowym arkuszu normalizacyjnym uzupełniającym normę EN 206-1.

agresja mrozu, beton napowietrzony, charakterystyka porów, klasa ekspozycji, wymagania normowe

W referacie przedstawiono wyniki badań betonu poddanego cyklicznym oddziaływaniom zmiennej temperatury i wilgotności wraz z zewnętrznym oddziaływaniem soli odladzającej. Warunki badania odzwierciedlają oddziaływania środowiskowe na beton w nawierzchniach dróg ekspresowych i elementach drogowych obiektów inżynierskich, określone kategorią środowiska E3. Próbki wykonano według receptur laboratoryjnych oraz pobrano na placu budowy kilku odcinków nawierzchni dróg ekspresowych w Polsce. Przeprowadzono pomiary ekspansji próbek betonu, zmiany masy i zmiany rezonansowego modułu sprężystości w funkcji czasu. W przypadku betonu nawierzchniowego pobranego na budowie, zawierającego kruszywa grube i drobne spełniające kryteria niereaktywności potwierdzono stabilność objętościową i stałość właściwości sprężystych. Wyniki badań próbek laboratoryjnych ujawniły zróżnicowaną podatność betonu na uszkodzenia wskutek ASR w warunkach zewnętrznego oddziaływania soli odladzającej, związaną z obecnością minerałów reaktywnych w kruszywach. Przeprowadzone międzylaboratoryjne badania porównawcze pod auspicjami BASt wykazały biegłość laboratorium.

Projektowanie betonu na osłony przed promieniowaniem jonizującym polega przedewszystkim na selekcji kruszyw o określonym składzie pierwiastkowym. Kruszywo serpentynitowe o dużej zawartości wody związanej chemicznie, zwłaszcza w układzie z kruszywem ciężkim (np. barytem), może być pożądanym składnikiem betonu w osłonach przed promieniowaniem mieszanym (neutronowym i gamma), narażonych również na oddziaływanie podwyższonej temperatury. Celem przeprowadzonych badań było rozpoznanie wpływu mieszaniny specjalnych kruszyw grubych o zmiennej proporcji kruszywa serpentynitowego i barytowego na wytrzymałość, mikrostrukturę i przepuszczalność betonu z cementem żużlowym. Badano wytrzymałość na ściskanie i współczynnik migracji jonów chlorkowych. Wyniki badań trwałościowych przedstawiono w kontekście wyników pomiaru porowatości otwartej, porowatości kapilarnej wraz z obserwacjami mikrostruktury na cienkich szlifach. Zaobserwowano zwiększoną porowatość warstw kontaktowych kruszywa z zaczynem cementowym. Wzrost porowatości otwartej i kapilarnej betonu okazał się skorelowany ze wzrostem współczynnika migracji jonów chlorkowych.

The exposed aggregate pavement technology for construction of concrete highways is used in European countries, including Poland, mostly for heavy trafficked strategic roads. It is mainly a two-lift slip-form technology with a special treatment of the top surface after the final smoothing operation. This is a demanding technology that leaves a little margin for mistakes. When properly done the pavement layer with exposed aggregates ensures designed skid resistance for vehicle wheels even in adverse weather conditions without excessive traffic noise. The challenge is to provide its cost-effective long term performance including both the adequate roughness and the desired smoothness of the pavement. The paper presents tools and methods for construction quality assurance specific for exposed aggregate concrete pavements. Required monitoring of the stability of concrete mix properties is discussed. The importance of concrete curing is analyzed in respect to the long term durability in wet-freeze regions with heavy use of deicing salts. Macrotexture assessment at the early stage of pavement construction is seen as the key factor for assurance of the proper skidding resistance. Local evaluation of smoothness is also a useful approach to assure the target IRI. Examples of quality assurance efforts applied on concrete highways recently constructed in Poland are presented.

air entrainment, exposed aggregate, evenness, jointed plain concrete pavement, quality assurance, macrotexture depth

Results of experimental investigations on the reactivity of crushed aggregates produced from sedimentary and igneous rocks are presented. Applied test methods, consistent with RILEM and ASTM standards are implemented in technical specifications of Polish national highway administration. The range of the investigations covered coarse aggregates produced from crushed limestone, dolomite, sandstone and greywacke rocks, as well as from basalt, melaphyre, porphyry, granite and gabbro. The aggregates were selected on the basis of their mechanical and physical properties to be adequate for making durable concrete for highway applications. The mineral composition of the aggregates was evaluated with regard to their reactive SiO2 content. A considerable amount of reactive minerals: chalcedony, tridymite and microcrystalline quartz were found in the grains of the porphyry and melaphyre aggregates. No reactive forms of quartz were found to be present in the mineralogical composition of the limestone aggregates and the dolomite aggregates. Micro- and cryptocrystalline quartz occurred in the particles of the greywacke aggregates and the sandstone aggregates. On the basis of the expansion of mortar and concrete of specimens, the coarse aggregates produced from crushed rocks were classified into three reactivity categories. A sodium-potassium-calcium silicate gel was found and its composition was consistent with that reported in the literature as characteristic of the alkali-aggregate reaction products. The tests revealed consistent assessment of the reactivity of the aggregates.

alkali silica gel, expansion tests, microcrystalline quartz, petrographic analysis, technical specifications

Stabilność właściwości mieszanki betonowej od momentu wymieszania do wbudowania wpływa na trwałość wykonanej konstrukcji. W przypadku betonu klasy projektowanego na agresję środowiska XF4 szczególnie istotna jest stabilność pęcherzyków powietrza wprowadzanych za pomocą domieszki napowietrzającej. Przedstawione badania rozważają wpływ stosowania cementów z dodatkami mineralnymi CEM II/A-V 42,5R, CEM II/B-S 42,5N i CEM III/A 42,5N na dystrybucję porów w mieszance betonowej przeznaczonej na górną warstwę nawierzchni betonowej. Przeanalizowano zmiany charakterystyki porów w betonie od wykonania do wbudowania. Próbki pobrano bezpośrednio po wykonaniu mieszanki, po godzinie bezruchu i po wysokoenergetycznym mieszaniu po godzinie bezruchu. Określono właściwości mieszanki betonowej, charakterystykę porów, właściwości mechaniczne, szybkość absorpcji wody i rezystywność betonu. Przeprowadzone badania wykazały utratę do 0,55% całkowitej zawartości powietrza w betonie po godzinie bezruchu. Wysokoenergetyczne mieszanie zwiększyło całkowitą zawartość powietrza o 1,57%, 1,02%, 0,92% odpowiednio w betonie z cementem CEM I, CEM II/A-V i CEM II/B-S. W betonie z CEM III/A zawartość powietrza zmniejszyła się o 0,69%. Wysokoenergetyczne mieszanie zwiększyło udział mikroporów - A300 w całkowitej zawartości powietrza w betonie z cementami żużlowymi przyczyniając się do zwiększenia o 8-12% tak wytrzymałości na ściskanie, jak i rozciąganie przy rozłupywaniu po 28 dniach dojrzewania. Pomiary rezystywności pozwoliły zaobserwować zwiększenie przepuszczalności próbek po dodatkowym mieszaniu. The stability of air bubbles in concrete mixture from homogenization to final embedding in pavement is necessary. The presented paper examine effect of using cements with supplementary cementitious materials, as CEM II / A-V 42.5R, CEM II / B-S 42.5N and CEM III / A 42.5N, on the air void distribution in the concrete mix intended for the upper layer of the concrete pavement. The fluctuation of air voids characteristics in concrete from homogenization to casting were analyzed. The specimens after mixing, one hours of inactivity and high-energy mixing after inactivity were taken. The concrete mix properties, air voids characteristics, mechanical properties, water absorption and hardened concrete resistivity were determined. The investigation revealed a loss up to 0,55% of total air content in concrete after one hour of inactivity. The high-energy mixing increased the total air content by 1.57%, 1.02%, 0.92% in concrete with CEM I, CEM II/A-V and CEM II/B-S respectively. The air content in CEM III/A concrete decreased by 0.69%. The high-energy mixing increased the share of micropores - A300 in the total air content in concrete with slag cements, contributing to 8-12% increase in both compressive and splitting strength after 28 days of curing. The resistivity measurements shown an increase in sample permeability after additional mixing.

During the decommissioning of nuclear power plants, a significant amount of cement based composites should be disposed as radioactive waste. The use of material with low-activation constituents could effectively reduce radioactivity of concrete. The subject of the paper is the content of trace elements with large activation cross section in concrete constituents due to their ability to be activated in radiation shielding structures. Various Portland cement specimens were subjected to elemental analysis by neutron activation analysis and prompt gamma activation analysis to assess the dominant long-lived residual radioisotopes. Concentrations of the radionuclides, such as Europium-152, Cobalt-60 and Caesium-134 were assessed. Their half-life time is 13.5, 5.27, and 2.07 years, respectively. On the basis of the obtained results, recommendations for cement selection for low-activation concrete are proposed in order to economize decommissioning cost by reducing a radioactive concrete waste.

Alkali silica reaction (ASR) is a harmful phenomenon occurring as a result of chemical interactions between sodium and potassium hydroxides in the pore solution and reactive minerals contained in the aggregate. Reactive minerals like microcrystalline, cryptocrystalline or strained quartz dissolve in the alkaline solution and form an expansive gel product. Proper selection of concrete constituents is necessary to ensure the durability of concrete structures. The proper recognition of the aggregate mineralogical composition is a very important element in the process of selection of concrete components due to the risk of ASR occurrence. This paper presents the results of detailed microscopic analysis of alkali-silica reactivity of domestic fine aggregates of various origins. Six siliceous sands from different locations in Poland and one limestone sand were tested. Detailed petrographic analysis was performed on thin sections. In all siliceous sands micro- and cryptocrystalline quartz was recognized as a reactive mineral. Digital image analysis was performed for quantitative assessment of the potential of reactivity of sands. It revealed, that siliceous river sands were the most susceptible to an alkali-silica reaction, which was confirmed by mortar bar expansion test performed according to the standard test method.

Prolonged durability of concrete structures is closely related to the minimization of the transport of liquids in cement matrix. Capillary suction is a dominant mechanism of liquid transport, especially in moderate climate, where cyclic wetting-drying and freeze-thawing cycles occur. Air-entraining of concrete is the efficient way to prevent deterioration impact from environment. However, the influence of air voids distribution on the capillary suction is not well known. The purpose of the research was to assess the water absorption properties of the air entrained concrete. The concrete mixes with the air content from 1% to 16% and similar proportion of micropores to large air voids (A300/A) were prepared. The water absorption tests were performed using ASTM C1585 procedure. The following parameters were determined: Si – initial rate of water absorption, Ss – secondary rate of water absorption, tn – time of nick point, In - water absorption for tn, I60 – initial 60 seconds of water absorption. The results were compared with the air content in concrete. Additionally the compressive strength, porosity accessible to water and concrete resistivity were measured. The linear relationships between initial and secondary rate of water absorption and the air content in concrete were found. A significant changes of rate of water absorption in concrete when the air content change more than 6% were observed.

water absorption, air-entrained concrete, nick point, concrete resistivity, porosity accessible to water

The risk of occurrence of deleterious alkali-silica reaction (ASR) in concrete should be properly minimized in major highway pavements and bridges. Real-life experiences show that even in concrete made with aggregates potentially not susceptible to ASR, it may occur under unfavourable conditions of external alkali supply at wet conditions and heavy traffic load. An experimental investigation was performed to study the susceptibility of selected Polish mineral aggregates to ASR at external alkali supply. The test method „60°C concrete test with external alkali supply” covered by draft procedure RILEM AAR-12 was implemented at IPPT PAN laboratory. Air entrained concrete specimens were exposed to cyclic temperature changes and wet-dry exposure as well as NaCl solution exposure. Several combinations of coarse crushed aggregate and fine natural aggregate were tested in concrete designed as for heavy duty highway pavement. SEM evaluation of microstructure of concrete with glacial deposit aggregate revealed visible alkali-silica gel. The effects of fine aggregate on the expansion of concrete were also revealed.

air entrained concrete, alkali-silica reaction, cyclic exposure, external alkali, highway pavement

Multicomponent cement-based composites are known as versatile structural materials for enhanced radiation shielding. The use of selected elements, like boron, cadmium, or rare earth elements, provides an increased neutron shielding capacity. Because of profusion, reasonable costs and large cross-section for neutron capture, boron containing minerals are suggested as aggregates for radiation shielding concrete. Despite many advantages, boron additives may act as cement setting retarders. Uncontrolled setting and hardening is not acceptable in radiation shielding concrete technology. In this work we present results from isothermal calorimetry measurements on cement mortars with boron-containing aggregates. Four types of boron aggregates were used in the studies: colemanite, ulexite, borax and boron carbide. Based on calorimetric curves, the beginning of setting time was determined. Additionally early mortar strength was investigated and linear relationship between the heat generated in the isothermal calorimeter and the early compressive strength has been observed. The use of isothermal calorimetry allowed us to estimate the limits for the content of boron compounds to be used cement mortar.

Salt solutions are used to ensure safe driving conditions during winter. NaCl deicer is the most often used brine in Polish climatic zone. The chemical effects of this type of chloride-based deicer in wetting and drying (WD) and temperature cycles on concrete need to be better understood. This research was focus to study the microstructure of air-entrained pavement concrete after combined chemical (10% of NaCl) and physical (WD and 60°C) exposure conditions. The adopted WD and temperature regime was designed to verify the hypothesis that regularly alternating wetting and drying cycles with external alkali supply from deicer salt will provoke the Alkali-Silica Reaction (ASR). The aggregates varied their origin and mineralogical composition. The microscopic examination was carried out on concrete specimens using SEM with EDX. The microscopic analysis has shown that main reason for concrete deterioration during cyclic chemical and physical exposure conditions was both physical influence - WD cycles and the chemical influence – ASR (primarily, the fine aggregate which lead to form of alkali-silica gel). The expansive gel was shown to be capable of destroying the test specimens. Also differences in mineralogical composition of coarse aggregates influenced on the concrete prism expansion due to ASR.

The long term performance of concrete pavements can be reduced due to improper selection of aggregates, thus prevention of damage due to alkali-silica reaction (ASR) requires a detailed examination of minerals in aggregates. The amount of reactive silica in the aggregate is an important factor governing the severity of ASR, which depends critically on the nature of the reactive aggregate. In the present study the potential for ASR in selected rocks in Poland was evaluated using petrographic methods. The tests were performed on crushed aggregates from different regions, covering a variety of rock origin and their geological structure. The optical microscopy in transparent light on thin sections was used as a principal tool to assess the mineral composition of aggregates. The content of reactive siliceous minerals was assessed. The petrographic examination concerned different forms of silica. Quartz grains were classified according to their mean diameter so as to identify the reactive range. The application of the petrographic method allowed for classification of aggregate for ASR potential using RILEM recommendation. The results of the study allow to make a quick and responsible decision to direct the aggregates to further detailed tests, reject or accept them as concrete components for concrete pavements.

alkali-silica reaction, polymineral grains, petrographic analysis

Penetration of external alkalis from deicing salts into concrete pavement can promote deleterious alkali-silica reaction (ASR) and therefore reduce its long-term performance. In severe exposure conditions (wet and heavy traffic load) the susceptibility of aggregates to ASR may be aggravated. To study this phenomenon on concrete specimens the combined cyclic exposure method was developed at VDZ Düsseldorf. Such a cyclic wet-dry-external alkali exposure was used on air entrained concrete specimens to investigate its influence on the microstructure and the permeability of concrete. Air voids characteristics, mercury intrusion porosimetry, porosity accessible to water and water absorption of concrete was tested. Concrete microstructure was observed in scanning electron microscope to reveal the specific features. The applied cyclic wetdry-external alkali exposure induced a marked decrease of total porosity of concrete and the appearance of ASR gel in cement matrix. An increase of the rate of water absorption of concrete was also found.

alkali-silica reaction, VDZ test, microstructure, permeability, water absorption

Przedmiotem referatu jest przydatność zmodyfikowanej metody ciśnieniowej do wyznaczenia charakterystyki porów w napowietrzonej mieszance betonowej w warunkach polowych na miejscu budowy nawierzchni drogowej. Metoda polegająca na stopniowym zwiększaniu ciśnienia na mieszankę, w określonej sekwencji, pozwala wyznaczyć parametr zwany liczbą SAM. Zgodnie z oczekiwaniem wynalazców metody powinna być skorelowana ze wskaźnikiem rozmieszczenia porów w betonie. Przeprowadzone badania doświadczalne obejmowały rozpoznanie w warunkach laboratoryjnych powtarzalności metody oraz pomiary napowietrzenia mieszanki na dolną i górną warstwę betonu w nawierzchni odcinków dróg ekspresowych. Na próbkach stwardniałego betonu wyznaczono wskaźnik rozmieszczenia porów zgodnie z PN-EN 480-11 i przeanalizowano zgodność charakterystyki napowietrzenia betonu stwardniałego z charakterystyką napowietrzenia mieszanki na podstawie liczby SAM. Wykonanie pomiarów w warunkach budowy dwuwarstwowej nawierzchni drogi ekspresowej nie nastręczało kłopotów technicznych. Jednakże w wielu przypadkach stwierdzono niewystarczającą korelację charakterystyki porów w mieszance i w betonie stwardniałym. Przeanalizowano czynniki wpływające na zaobserwowane niezgodności.

Exposed aggregate concrete (EAC) pavement technology is used in Poland for construction of major highways and expressways. When properly executed, it is an efficient technique to provide desired friction for skid resistance without compromising the noise limitations. Concrete mix uniformity, proper dosing of retarding agent and optimal time to brush with a mechanical broom are supposed to have a major impact on the properties of the upper pavement layer. An experimental investigation was performed on exposed aggregate concrete specimens manufactured in the laboratory in a way to simulate the industrial production of two-layer concrete slab with exposed aggregate. The texture depth was determined using a laser profiler. The compressive strength of concrete, the water absorption rate, and permeability of chloride ions through concrete were also determined. The freeze-thaw resistance and surface scaling resistance were tested and analyzed with respect to air void characteristics. Results revealed an increase in surface scaling for EAC slabs with higher w/c ratio and slabs simulating local bleeding. The most efficient method to determine indirectly the durability of EAC slabs was the set of permeability tests comprised of measurements of chloride migration and rate of water absorption. The change of macrotexture depth with increase of w/c ratio and retarding admixture type was found.

highway pavement, exposed aggregate concrete, surface retarder, durability, concrete preparation parameter, water absorption, chloride migration, surface scaling, macrotexture

Crushed granite aggregates due to good physical and mechanical properties are widely accepted for production of durable concrete. This kind of aggregates are considered as not alkali-silica reactive (ASR). However, all of them contain silica. In some of them SiO2 occurs in a strained form or the crystals are small enough to be treated as microcrystalline, so they can be prone to ASR. Various granite aggregates taken from largest exploited Polish quarries were tested. Petrographic analysis on thin sections and accelerated mortar-bar test were carried out to assess potential of the alkali-silica reactivity. The petrographic analysis revealed differences in mineral composition of the tested granites. The strained quartz and microcrystalline quartz were the main potentially deleterious mineral in analyzed granite aggregates. Also the myrmekites were particularly visible in the granitic rocks. The results of the mortar-bar tests confirmed such predictions. The mortar beams showed expansion more than 0.1% after 28 days of exposition in 1M NaOH and 80°C. The bars made with RILEM cement showed fast and large elongation. In all cases the increase in mortar beam elongation was linear. The SEM-EDS analysis confirmed the presence of the ASR gel both, in the aggregate and in the matrix.

This paper features the development of a probabilistic model linking freeze-thaw (F-T) performance of concrete mixtures to their composition. As part of the process of model development, a sensitivity analysis was performed on several concrete mixture parameters to identify these factors that have strong correlations with the F-T resistance of concrete. This sensitivity analysis was performed on 128 sets of experimental F-T test results collected from the literature. The F-T performance level was defined as a discrete measure of the frost resistance of concrete. Finally, a new model to predict the F-T damage of concrete incorporating the variability of the concrete mix parameters (as selected from sensitivity analysis) was developed. This model was developed using only these data sets which contained the results of the relative dynamic modulus of elasticity (RDME) testing performed according to the ASTM C 666 (AASHTO T 161) specifications. Furthermore, only mixtures containing ordinary portland cement (OPC) as a sole type of the binder (i.e., mixtures that did not contain any supplementary cementitious materials) were considered. Additional experimental test results were utilized to validate the model. The reliability of the model was further demonstrated using several examples 1 of concrete mixtures of various compositions. Furthermore, the effects of the number of F-T cycles, air content, paste content, and w/c ratio on the F-T performance of the concrete mixes were demonstrated using the developed model. Accordingly, this model provides the opportunity to optimize the concrete mix proportion for the required performance level of concrete under F-T exposure condition.

Freeze-thaw, durability, concrete, pavement, sensitivity analysis, probabilistic design

In the present study, the potential for the alkali–silica reaction (ASR) in radiation shielding concrete containing special aggregates is presented. The tests were performed on two kinds of aggregate: (1) high-density aggregate to absorb the gamma radiation (barite, magnetite, and hematite) and (2) mineral with high bound water content to attenuate the neutron flux (serpentinite). The optical microscopy in transparent light on thin sections, XRD and XRF method, was used to assess the mineral composition of aggregates. ASTM C1260 test method for potential alkali reactivity of aggregates was applied also to investigate the effect of different content and crystal size of silica on the expansion due to ASR. The tests revealed that all tested aggregates, such as barite, magnetite, hematite, and serpentinite, were characterized by low solubility at high pH. The XRD and XRF results have shown presence of silica in all tested aggregates, but the microscopic observations enhanced size and composition of SiO2 crystals. The aggregates were not deleterious themselves, but the different content and size of SiO2 crystals in the aggregate influenced their potential for alkali–silica reaction. The quartz in heavy kinds of rocks and in the serpentinite used for radiation shielding was just as much potentially susceptible to deleterious ASR as quartz in common rocks used in concrete technology. In the hematite, silica crystals were classified as microcrystalline, so it should be considered as potentially reactive. The expansion tests confirmed that hematite was highly reactive. Other aggregates after 14 days of testing did not exceed 0.1% elongation limit. The microstructural analysis of thin sections prepared from mortars after ASTM C1260 test confirmed expansion of aggregate grains due to ASR.

Alkali-Silica Reaction (ASR), ionizing radiation, high density aggregate

Przedstawiono wyniki badań cementów, przeznaczonych do stosowania jako spoiwo w technologii wykonawstwa betonowych osłon przed promieniowaniem jonizującym w energetyce jądrowej. Zakres badań objął cementy spełniające wymagania stawiane cementom specjalnym o niskim cieple hydratacji, odpornym na siarczany oraz o niskiej zawartości alkaliów. Badano cementy powszechnego użytku; portlandzki CEM I bez dodatku mineralnego oraz wieloskładnikowe z dodatkami mineralnymi. Wykonano cementy specjalne z normowymi dodatkami mineralnymi oraz z dodatkami nie ujętymi w normie cementowej PN EN 197-1, stosując autorskie rozwiązania, dotyczące produkcji cementów z proszkowym dodatkiem minerałów ciężkich: barytu, magnetytu i getytu. Na podstawie przeprowadzonych badań cementów wykazano specjalne właściwości tych cementów w zakresie niskiego ciepła hydratacji i odporności na siarczany, w przypadku cementu portlandzkiego oraz cementów z dodatkami mineralnymi ujętymi w normie PN-EN 197-1. Stosowanie cementów normowych do betonu zwiększa odporność na reakcję kruszywa z wodorotlenkami sodu i potasu w betonie, nawet niwelując ekspansję betonu z dodatkiem kruszywa reaktywnego. Stosowanie CEM III/A 42,5N LH/HSR/NA w miejsce CEM I 42,5N LH/SR3/NA w betonie ciężkim o gęstości 3200-3600 kg/m3 spowodowało spadek współczynnika szybkości absorpcji wody, zmniejszenie współczynnika migracji jonów chlorkowych oraz zwiększenie szybkości karbonatyzacji. Zaobserwowano znaczny wpływ zróżnicowania rodzaju kruszywa w betonie ciężkim na wytrzymałość i wskaźniki nieprzepuszczalności betonu.

Celem projektu Reaktywność alkaliczna krajowych kruszyw, ASR-RID jest opracowanie wytycznych technicznych projektowania betonów o dużej trwałości, ze szczególnym uwzględnieniem zabezpieczenia przed wystąpieniem uszkodzeń spowodowanych reakcją AAR – alkali aggregate reaction, tj. między NaOH i KOH, a reaktywnymi minerałami w kruszywie. Przedmiotem badań są kruszywa ze złóż z różnych regionów Polski. Reaktywność alkaliczna kruszyw jest oznaczana i oceniana przy wykorzystaniu komplementarnych metod, stosowanych w systemach oceny reaktywności kruszyw w wiodących technologicznie krajach. Projekt zakłada opracowanie kryteriów oceny reaktywności kruszyw, z możliwością wykorzystania w systemie kontroli produkcji i ich dostaw na potrzeby wytwarzania betonów drogowych. Opracowane receptury betonów uwzględniać będą możliwość zapobiegania AAR poprzez ograniczenie zawartości czynnych alkaliów, stosowanie cementów NA i dodatków mineralnych wprowadzanych z cementem. Ocena reaktywności będzie zweryfikowana na podstawie ekspansji betonu w warunkach eksploatacyjnych. Przyjmując kryteria oceny zakłada się uwzględnienie doświadczeń krajowych oraz rekomendacji norm ASTM i RILEM zapobiegania reakcji AAR. Projekt Reaktywność alkaliczna krajowych kruszyw, Nr RID-I/37, jest realizowany od stycznia 2016, w ramach programu Rozwój Innowacji Drogowych (RID) finansowanego przez Narodowe Centrum Badań i Rozwoju oraz Generalną Dyrekcję Dróg Krajowych i Autostrad przez konsorcjum naukowe, ASR-RID, zawiązane pomiędzy Instytutem Ceramiki i Materiałów Budowlanych oraz Instytutem Podstawowych Problemów Techniki PAN. W artykule przedstawiono wstępne wyniki badań reaktywności kruszyw przy wykorzystaniu szybkich metod oceny – metody chemicznej ASTM C 289 oraz metody pomiarów ekspansji zaprawy wg ASTM C 1260.

The use of exposed aggregate concrete (EAC) in the upper layer of two-lift pavements is spread over many European countries including Poland. However, the EAC technology is considered difficult to apply because of inevitable dependence on operator's experience to control the whole process properly. The proper timing of technological operations is critical. The investigation on the performance of EAC was performed to gain a better understanding of material and environmental factors involved. EAC slabs were manufactured in the laboratory following the procedure applied at the construction site. Air entrained concrete mix design included a variable water to cement ratio and cement type while the type and the content of aggregate was constant. The effects of curing intensity were studied. The strength properties, air void characteristics of hardened concrete, the freeze-thaw resistance and the salt-scaling resistance were tested of specimens cored from the slabs, using the European standard methods. EAC permeability was also evaluated using the methods covered by ASTM C1585 and NT Build 492. Such permeability indicators and frost durability were applied to evaluate the differences in EAC layers performance. The environmental vulnerability of EAC mixes used in the upper layer of two-lift pavements is discussed.

air entrainment, blended cement, concrete durability, curing technology, highway pavement, mix design, permeability

Nuclear reactor containments must maintain high durability since they restrict the spread of radiation and radioactive contamination to the general public, which could have significant consequences. The containment integrity and impermeability for potentially contaminated media is ensured using sophisticated structural and materials solutions including prevention of early age cracking of concrete. The results of numerical and experimental investigation on thermal behavior of early age concrete are presented. Concrete mixes were prepared with low-heat blended cements and various mineral aggregates. Special aggregates were selected for enhancing the radiation shielding capacity of concrete, including minerals of high atomic weight and of increased content of bound water. The proposed approach consisted of several stages, consisting mainly of measurements of the one-dimensional heat distribution in cylindrical concrete elements and solving the equation of one-dimensional heat transferto determine thermal properties of hardening concrete. The proposed model of temperature distribution in hardening concrete is based on the non-linear inverse heat transfer problem solution. The obtained experimental results and numerically determined material characteristics are discussed in respect to the concrete mix design.

durability, heat transfer, hardening concrete, inverse solution, temperature, thermal properties

The relationship between the internal pore characteristic and the non-steady state chloride migration coefficient (Dnssm) was investigated for concrete mixes made with blended cement containing high calcium fly ash (HCFA). Air entrained concrete mixes were made usinggranodiorite and crushed limestone as coarse aggregate. Designed surface scaling resistance was confirmed with standard test. The pore structure was determined using mercury intrusion porosimetry (MIP) and digital image analysis techniques. Phase composition of hydration products was examined using the XRD analysis. Chloride ion transportvelocity was measured using a rapid chloride migration test.The test has shown a relationship between the chloride migration coefficient and poresizecharacteristic derived from MIP tests. Effect of aggregate type on the course of relationship as shown differences curve for both type of aggregates. Increase amount of additives in blended cements caused decrease of critical and average pore size obtained by MIP method.

HCFA, blended cement, chloride ions migration, MIP, scaling resistance

In the present study the potential appearance of the alkali-silica reaction (ASR) in heavy aggregates was studied. ASTM C1260 Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method) was applied. In order to investigate the effect of the content of alkalies in cement on the expansions due to ASR, three levels of total and soluble alkali content of cement were studied. Three portland cements Type I with different alkali content were selected. Two ordinary portland cements, which are commonly available in the market and one special cement were tested. That cement was specially made for the purpose of the nuclear shielding concrete CEM I NA-SR-LH of low-alkali, increased sulphate resistance and low heat of hydration. For the tests according to ASTM C 1260 the high-density aggregates, known as absorbing gamma radiation were selected: barite, magnetite and hematite. The expansion test revealed that hematite was highly reactive, regardless of the type of cement. Already after four days of storage in 1 N NaOH and 80°C the mortar bar expansion exceeded the limit of 0.1%, and after next four days was more than 0.2%., which qualifies it extremely reactive aggregate. Other aggregates after 14 days of testing did not exceed 0.1% elongation limit, but the influence of the type of cement was noticed. There was a noticeable tendency for increasing the total expansion with increasing the alkali content of cement.

Alkali-Silica Reaction (ASR), high density aggregate, cement composition

The paper presents the results of investigation of the specific heat and the thermal conductivity of shielding concrete and the specific heat of selected crushed aggregates used to produce them. The results of the specific heat were obtained by two methods: a stationary method, using a calorimeter, and a non-stationary method. The obtained results were compared to the results available in the literature. In addition, in the case of measuring the specific heat, the results obtained with the two methods were compared and attempt has been made to explain the differences between them.

shielding concrete, heavy aggregates, specific heat, thermal conductivity

Construction industry demands large quantity of recycled materials for sustainable development. The use of recycled aggregate (RA) as a replacement for natural aggregate (NA) represents a sensible approach from technical, environmental, and economic points of view. Due to the substantial differences in the properties of RA and NA, predicting the performance of recycled aggregate concrete has been a concern in many design applications. In this study, M5´ model tree algorithm was used to develop a new model to predict the compressive strength of recycled aggregate concrete. Compared to other soft computing methods, the model tree algorithms offer the following advantages: (a) greater transparency with respect to development of model equations and (b) relative ease of development and implementation. To develop the model tree, 270 data sets were collected from international published literature. The results show that the developed model tree algorithm can well predict the compressive strength of recycled aggregate concrete.

M5´ model tree, modulus of elasticity, recycled aggregate, concrete

The results of microscopic analysis on thin sections of aggregates intended for nuclear shielding concrete are presented. The petrographic analysis was performed on different barite, magnetite and hematite aggregates used as the high-density aggregate to absorb gamma radiation. Both optical microscopy and accelerated expansion tests were used to recognise the potential for alkali-reactivity of the aggregates. The mineral composition of the tested aggregates was analysed on thin sections in transmitted cross-polarized light and XRD tests were additionally performed. Expansion tests of mortar bars exposed to 1 N NaOH solution at the temperature of 80°C were also performed following ASTM C1260. The high-density aggregates contained ore deposits - metallic opaque phases providing the required shielding properties. These aggregates also contained various amounts of non-metallic phases, with both innocuous non-ore minerals and deleterious, potentially reactive materials. Barite aggregates contained siderite, fluorite and hawleyite in varying amounts, apart from the barium sulphate being the principal component. Moreover, particularly reactive cristobalite and muscovite were identified in barite aggregates from certain quarries. Tests according to ASTM C1260 performed on mortars showed the expansion above the accepted criterion for non-reactive aggregate and confirmed the threat due to the presence of cristobalite in barite aggregates.

high-density aggregate, heavy concrete, alkali-silica reaction, thin section, XRD

The construction of Żarnowiec Nuclear Power Plant (NPP) facilities was discontinued in 1989, despite the high level of work advancement. Already a large part of the concrete structures was built, now submerged in water from Żarnowieckie Lake. These structures were exposed over 30 years to the environmental conditions (rain, and varying high and low temperatures) without any special maintenance treatment. The technological documentation archives are not available. Experimental testing of specimens drilled out from different concrete structure elements was performed in September 2014.
The goal of the research was the identification of the composition of concrete and its present properties, especially the recognition of the effects of long-term environmental impact. The scope of the research covered macroscopic and microscopic analysis of concrete, compressive strength test, permeability test defined as the rate of chloride ions migration and water absorption. Unfortunately, the most important parts of the concrete structure are not available for testing because they are under water level. The obtained results allowed to classify the concrete structural elements in nuclear power plants buildings as of a quite good quality.

durability, old concrete, strength, microstructure, permeability

W referacie przedstawiono wymagania na skład betonu odpornego na agresję mrozu zgodnie z PN-EN 206 oraz sposób projektowania metodą doświadczalną. Pojęcie mrozoodporności betonu nie jest absolutne, lecz względne – odnosi się do konkretnych warunków ekspozycji betonu na działanie wilgoci, szybkości i amplitudy zmian temperatury oraz intensywności stosowania środków odladzających. Dlatego omówiono lokalne zróżnicowanie agresywności klimatu w zimie i zasięg oddziaływania mrozu w konstrukcjach. Przeanalizowano charakterystyczne cechy procedur bezpośredniego oznaczania mrozoodporności, w tym możliwości modyfikacji oznaczania „stopnia mrozoodporności”. Przedstawiono też kryteria oceny mrozoodporności oznaczanej metodą pośrednią, zwłaszcza w odniesieniu do obiektów inżynierskich i nawierzchni drogowych z betonu.

charakterystyka porów, metody badań, mrozoodpornooeść wewnętrzna, projektowanie mieszanki, szybkoość ochładzania, trwałoość, wymagania funkcjonalne

The use of high calcium fly ash from brown coal combustion in Balchatow Power Plant in Poland as one of major components of common cements was studied. The strength and the permability of concrete made with blended cements CEM II and

air permeability, blended cement, calcareous fly ash, ternary cement, water penetration

A numerical and experimental investigation on thermal behavior of young concrete is presented. It haseen performed to establish the range of possible applications of concrete containing non-standard addition of reactive high calcium fly ash. The proposed model of temperature distribution in hardening concrete is based on the non-linear IH TP (inverse heat transfer problem ) solution. Changes in properties of concrete during setting and hardening are included in the model. The proposed approach consists of several stages. First the temperature measurements in a one-dimensional form are performed using real size concrete materials. Then the method of lines is used to solve the one dimensional heat equation. The results are treated as an input to IHTP for determination of thermal properties of concrete: specific heat capacity, thermal conductivity and heat of hardening. To solve IHTP the pattern search method is used, which does not require the calculation of the gradient of the objective function. In the third step the direct heat conduction problem is solved. Own, based on finite element method, software TMC (Thermal & Mechanical modeling of Concrete) is used to predict temperature field. The obtained numerical results have been compared with experimentally measured temperature in concrete and a fair agreement has been found

early age concrete, inverse problem, heat transfer, high calcium fly ash

The possibility of using the high calcium fly ash (HCFA) as type II concrete additive is not well established, especially in relation to the durability of concrete structures in aggressive environment. The paper presents results of microstructural characterization of air-entrained concrete containing high calcium fly ash from lignite combustion. Frost resistant concretes were designed with different content of fly ash use for cement replacement by 15% and 30%. Different kinds of HCFA were used: raw (unprocessed) and grinded during 10, 15 and 28 minutes. The evaluation of the microstructure was performed using SEM and optical microscopy on thin sections and plane sections. All thin sections were impregnated with epoxy containing fluorescent dye and were examined using ordinary light, crossed polarized light and UV light. The thin section evaluation involved petrographic characterization of aggregates and examination of paste quality. Automatic air-void analysis on plane sections revealed air-content, specific surface, spacing factor and the content of micropores in the hardened concrete. Significant differences in particle shape and size before and after grinding of the HCFA were revealed by SEM analysis. The results of thin section analysis of the high calcium fly ash concrete showed that its microstructure was more dense than that of the ordinary concrete. The influence of specific surface of fly ash on air void content in HCFA concrete was found.

high calcium fly ash (HCFA), air-entrained concretes, microstructural characterization

In this paper the resistance to chloride penetration into concrete containing various high-calcium fly ashes (HCFA) from brown coal combustion in power industry is examined. HCFA from Belchatow Power Plant was used as nonstandard concrete additive for partial replacement of cement in the mix. To evaluate the concrete resistance to chloride ion penetration the standard method of determination of chloride migration coefficient from non-steady-state migration test according to NT Build 492 was used. The range of investigation included fly ash grinded to specified specific surface as well unprocessed fly ash. Test results revaled a substantial improvement of the resistance to chloride penetration into concrete containing HCFA as partial replacement of Portland cement. The resistance was higher for increased replacement level and decreased water-to-cement ratio. Favourable effects of high-calcium fly ash are discussed in relation to k-factor concept

chloride penetration, high calcium fly ash, cement replacement

The investigation of the influence of solid residue from hard coal combustion in circulating fluidized bed boilers on the strength of concrete was performed. The ash samples from power plant were collected regularly during 12 months to allow evaluation of variability of ash properties. Cementitious mixes were designed at the constant workability and batched using fluidized bed ash for partial replacement of Portland cement CEM I. The compressive strength of concrete at the age beyond 28 days was found to increase due to FBC ash addition for replacement of 20% of cement. The efficiency of fluidizied bed ash as potential type II concrete additive was evaluated using Bolomey's and Feret's formulas for the compressive strength of concrete. The efficiency factors were established at the age of concrete up to 1 year

cement replacement, efficiency factor, fluidized bed fly ash, strength of concrete, type II additive

This paper presents concrete mix design as well as the results of testing of concrete during production of precast foundations for wind power turbines which are to be located in the Baltic Sea. From 2002 to 2010 approximately 120 000 m3of concrete was cast to form 210 foundation blocks. Concrete production and casting was performed in Poland and the manufactured concrete blocks were transported to wind farms in Denmarkand Sweden. Massive reinforced concrete blocks were designed to be laid at the sea bottom about 7.5-12.5 m below the water level. For concrete mix design the following exposition classes were assumed: XC4, XF4, XS3 and XM3 according to EN 206-1. Exposure to exceptionally severe environmental conditions was assumed: chemical aggression and mechanical wear by seawater, freezing and thawing in saltwater. Because of thelarge size of blocks the danger of thermally induced cracking of concrete was carefully considered and computer simulation of stress build-up was used to select the optimal solution. Concrete mix C45/55 was designed using cement CEM III/A 32.5N HSR NA (containing about 60%GGBFS), silica fume, crushed aggregates up to 32 mm and water-reducing and air-entraining additives. High durability of concrete in the aggressive environment was predicted on the basis of microscopic testing of cement hydration products and quantitative evaluation of microstructure. The challenging issue was to maintain a stable air void system in concrete during the whole production process: air void characteristic was regularly monitored in fresh concrete using AVA and in hardened concrete using computer image analysis.Heat of hydration data and monitoring of temperature during concrete hardening provided necessary proof of a non-cracked structure

durability of concrete, air void system in concrete, sustainable production, heat of hydration

Przedstawiono zagadnienia związane z jakością prefabrykowanych, betonowych pokryw studni kanalizacji kablowej, wbudowanych w nawierzchnie drogowe. Przeprowadzono badania doświadczalne właściwości mechanicznych i trwałości betonu przeznaczonego do wykonania prefabrykatów. Wykonano badania nośności całych prefabrykatów, wykonanych w różnych zakładach produkcyjnych na podstawie opracowanych recept betonu. Przeanalizowano wpływ rodzaju cementu, domieszek chemicznych i zbrojenia rozproszonego na nośność prefabrykatów betonowych oraz na odporność betonu na oddziaływania klimatyczne i eksploatacyjne. Wnioski z pracy badawczej odnoszą się do konstrukcji pokryw oraz przydatności pokryw do zastosowań w ciągach dróg dla pieszych i pojazdów.

konstrukcja pokryw, nośność, skład betonu, trwałość, właściwości mechaniczne, zbrojenie rozproszone

Przeprowadzono badania doświadczalne przepuszczalności powietrza przez beton przy zastosowaniu nieniszczącej metody Torrenta. Zaprojektowano i wykonano płyty betonowe z mieszanek o jednakowym stosie okruchowym i zróżnicowanym spoiwie poprzez zastosowanie dodatków popiołowych. Wykonane elementy próbne pielęgnowano w warunkach normowych wysokiej wilgotności, a później poddano suszeniu w warunkach laboratoryjnych. Przeprowadzono pomiary współczynnika gazoprzepuszczalności kT oraz oporu elektrycznego sondą Wennera. Ponadto, przeprowadzono normowe określenie wytrzymałości betonu na ściskanie. Jak stwierdzono, współczynnik gazoprzepuszczalności kT betonu zwiększał się o dwa rzędy wielkości wskutek wysychania elementów próbnych. Przydatność sondy Wennera do pośredniego określenia wilgotności betonu była ograniczona. Stwierdzono istotny wpływ modyfikacji popiołowych na współczynnik przepuszczalności powietrza przez beton.

beton, gazoprzepuszczalność, popiół lotny, wilgotność, wytrzymałość na ściskanie

Celem rozpoczętych badań jest ocena przepuszczalności betonu zawierającego popiół lotny wapienny pochodzący ze spalania węgla brunatnego w energetyce zawodowej, w szczególności jakościowe rozpoznanie i określenie ilościowe wpływu składnika popiołowego w cemencie lub dodatku popiołu do betonu na wnikanie mediów agresywnych. W referacie przedstawiono podstawowe koncepcje badawcze oraz wyniki określania szczelności betonu na podstawie literatury. Stwierdzono, że można oczekiwać korzystnych efektów stosowania popiołu lotnego wapiennego, ujawniających się znaczącą redukcją współczynnika dyfuzji i współczynnika migracji chlorków, a także efektów niekorzystnych polegających na zwiększeniu przepuszczalności powietrza i ewentualnie podwyższeniu szybkości karbonatyzacji.

popiół lotny wapienny, trwałość, beton

Celem projektu „Innowacyjne spoiwa cementowe i betony z wykorzystaniem popiołu lotnego wapiennego” jest opracowanie innowacyjnej i efektywnej kosztowo technologii nowych spoiw cementowych oraz betonów powstałych z wykorzystaniem popiołów lotnych wapiennych, będących efektem spalania węgla brunatnego w elektrowniach. W rozdziale przedstawiono genezę, przedmiot, cele, założenia i program projektu. Wdrożenie efektów projektu praktycznego stosowania może wygenerować następujące korzyści gospodarcze i techniczne: ograniczenie kosztów wytwarzania cementu dzięki redukcji emisji C02 w procesie produkcyjnym, możliwość użycia nowego materiału (wapniowych popiołów lotnych) w miejsce coraz trudniej dostępnych żużla wielkopiecowego i popiołu lotnego krzemionkowego, rozszerzenie bazy surowcowej dla przemysłu cementowego i betonów, możliwość wykonania nowych, dotychczas nie produkowanych w Polsce, rodzajów cementów o właściwościach istotnych z punktu widzenia krajowego rynku budowlanego oraz utrzymanie konkurencyjności przemysłu cementowego.

innowacyjne spoiwa, popiół lotny wapienny, zagospodarowanie ubocznych produktów spalania, założenia projektu

Możliwości zastosowania popiołów lotnych wapiennych jako dodatków typu II do betonów konstrukcyjnych nie są dostatecznie rozpoznane, szczególnie w zakresie zagadnień trwałości betonów zawierających takie popioły. Referat przedstawia wyniki badania stabilności porów powietrznych w mieszankach betonowych, zawierających popiół lotny wapienny oraz wyniki badania charakterystyki porów powietrznych w betonie stwardniałym. Mieszanki betonowe napowietrzne zaprojektowano zgodnie z wymaganiami wysokiej odporności betonu na agresję mrozu i środków odladzających. Część cementu portlandzkiego zastępowano popiołem lotnym wapiennym, przy założeniu współczynnika efektywności dodatku. Na wykonanych próbkach betonu przeprowadzono badania parametrów mikrostruktury porów powietrznych i sformułowano wnioski dotyczące możliwości napowietrzania mieszanek zawierających popiół lotny wapienny.

charakterystyka porów powietrznych, dodatek typu II, mrozoodporność, napowietrzanie, popiół lotny wapienny, trwałość

W artykule omówiono podstawowe pojęcia dotyczące zbrojenia strukturalnego betonu, sposoby projektowania mieszanki betonowej oraz wpływ włókien na właściwości mechaniczne i fizyczne betonu. Omówiono charakterystykę mikrostruktury zbrojenia rozproszonego. Przedstawiono także uproszczony sposób obliczania grubości fibrobetonowych podłóg na gruncie i założenia obliczeniowe elementów konstrukcyjnych metodą RILEM.

beton, odporność na pękanie, projektowania mieszanki, rozmieszczenie włókien, właściwości mechaniczne, wymiarowanie elementów konstrukcyjnych, zbrojenie rozproszone

air entrained concrete, air voids characterization, ASR performance test, concrete durability, job mixtures, materials selection

The evolutionary computation procedures in identification of thermophysical properties of hardening concrete in massive structures are presented. Heat of cement hydration, thermal conductivity and specific heat are determined for purpose of modelling temperature evolution in massive concrete elements. The knowledge of temperature fields is very important due to a link with undesired thermal stresses, which can cause a weakening of the structure because of thermal cracking. The proposed method is based on point temperature measurements in a cylindrical mould and the numerical solution of the inverse heat transfer problem by means of finite element method and evolutionary computation

heat of cement hydration, inverse heat transfer problem, early age concrete, evolutionary algorithm, finite element method, thermophysical properties of concrete

kruszywa łamane, reakcja AAR, analiza petrograficzna

beton osłonowy, elektrownia jądrowa, osłony radiologiczne, projektowanie, trwałość

reaktywność alkaliczna kruszyw, kruszywa mineralne, klasyfikacja krajowych kruszyw