Institute of Fundamental Technological Research

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

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

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

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

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

The assessment of the aggregate suitability for concrete pavements applies mainly to coarse aggregate. However, even fine aggregate can significantly affect the long-term durability of concrete when it is susceptible to alkali-silica reaction (ASR). The sustainable use of available fine aggregates for the production of concrete, while reducing the effects of ASR, requires special preventive measures. The paper proposed different procedures to determine the chemical composition of aggregate and the related ASR risk. The study covers various properties of natural fine aggregates from glacial deposits. The experiments included determination of chemical composition by prompt gamma activation analysis (PGAA), quantitative mineralogical characterisation on thin sections using digital image procedure (DIP) and expansion measurements in mortar bar test (MBT). The strong correlation of sand origin and its susceptibility to ASR was observed. Content of micro- and cryptocrystalline quartz in siliceous sand was found to have a crucial effect on its performance in AMBT.

fine aggregate, alkali-silica reaction, mineral composition, prompt gamma activation analysis, digital image procedure, glacial deposit

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

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

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

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

Możliwość wystąpienia reakcji alkalicznej wodorotlenków sodu i potasu (Alkali Silica Reaction, ASR) w betonowych osłonach reaktorów wymaga szczególnej ostrożności przy doborze składników betonów do realizacji programu energii jądrowej w Polsce. Uszkodzenia osłon reaktorów w USA i w Belgii wskazują kierunki niezbędnych badań, [1-3]. W badaniach przedstawionych w artykule zastosowano kruszywa o dużej gęstości (osłabianie promieniowania gamma): magnetytowe, barytowe oraz hematytowe oraz kruszywo o wysokiej zawartości wody związanej (absorpcja promieniowania neutronowego) – kruszywo serpentynitowe. Przeprowadzono badania mikroskopowe kruszyw na cienkich szlifach w celu identyfikacji potencjalnie szkodliwych minerałów z uwagi na zagrożenie ASR, oraz przyspieszone i długotrwałe badania w celu określenia potencjalnej reaktywności alkalicznej tych kruszyw. Wyniki badań wykluczyły możliwość stosowania kruszywa hematytowego do betonów osłonowych. Wyniki badań odnośnie do wykorzystania dostępnych kruszyw specjalnych tworzą podstawy projektowania bezpiecznych osłon w warunkach krajowych

reakcja krzemionki z wodorotlenkami sodu i potasu (ASR), ekspansja, beton osłonowy, kruszywo specjalne

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

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

Concretes for the shields against ionizing radiation should be executed with particular care to satisfy all requirements, not only effective attenuation of different radiation but also sufficient durability. In the paper fundamental problems are presented that are related with designing of such protective concretes in order to avoid alkali-aggregate reaction. The results of preliminary investigations are presented that indicate how to select barite aggregate and to define composition of concrete mix. Present knowledge in that area of materials engineering should be completed before initiation of construction of nuclear power stations at industrial scale in Poland.

Alkali Aggregate Reaction (AAR), heavy aggregate, ionizing radiation

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 purpose of this research was to determine the carbonation depths in concrete containing calcareous fly ash. Eleven concrete mixes with the same water-binder ratio w/b and with different amounts of calcareous fly ash have been prepared in laboratory. In the test series I the mixes were produced with five blended cements containing different amounts of the following supplementary cementitious materials: calcareous fly ash, siliceous fly ash and granulated blast furnace slag. The second test series was produced with calcareous fly ash replacing 30% of the cement by weight. The maximum depth of carbonation in concrete was determined using the phenolphthalein method. The progress of the carbonation front was established by analysing polished thin sections of concrete under a polarizing microscope in transmitted light. The most resistant to carbonation was the concrete containing, beside clinker, 14.3% of calcareous fly ash as a cementitious material. The specimens of concrete containing different amounts of calcareous fly ash were compared and no significant variations were found both in the rate and depth of carbonation. On the other hand, the rate of advancement of carbonation front was higher in concrete containing calcareous fly ash as compared to the reference concrete without admixtures.

blended cements, calcareous fly ash, carbonation, particle size separation of fly ash

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

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 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.

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

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.

In the present study the potential of alkali-silica reaction (ASR) in fine fraction of aggregate was analyzed. The investigation was focused on mineral composition of siliceous sand and its influence on ASR. Three siliceous sands from different origin and localization in Poland were tested. Petrographic analysis on thin sections was conducted. The automatic image analysis was used to estimate the content of reactive minerals (micro- and crypto-crystalline quartz). The XRD measurements were performed. Alkali-silica reactivity of fine aggregate was tested by mortar-bar test according to ASTM C1260 Standard. Petrographic analysis showed that all tested siliceous sands contained reactive form of quartz, micro- and cryptocrystalline. Mortar-bar tests according to ASTM C1260 indicated that one from the selected sands exceeded expansion over the limit and was considered as reactive. The content of reactive minerals in sands estimated by automatic image analysis corresponded to ASTM C1260 results. The higher content of reactive form of quartz in siliceous sand, the larger expansion of mortar-bar test.

Siliceous sand, Alkali-Silica Reaction (ASR), digital image analysis, micro- and cryptocrystalline quartz, expansion

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

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

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

The addition of natural fibers residue in cement based materials can be a sustainable technological alternative for traditional dispersed reinforcement, and can improve the performance of brittle matrix materials. The presence of a wool reinforcement can increase the fracture toughness and, at the same time, can reduce the environmental impact of cementitious mortars. The beneficial effects are similarly to those observed in presence of vegetal fibers (e.g., hemp), which have been largely investigated in the literature. However, there are some limits in the use of wool fibers due to their chemical compatibility with the cement matrix, as they can dissolve in alkaline environments. In the present paper, to investigate the compatibility between wool fibers and cementitious mortars, laboratory prototypes have been taken into consideration. Three series of wool-reinforced mortar beams have been cast and cured in water (20°C) or in dry conditions (temp. 20 °C, 50% R.H.) for some days. Portland-limestone cement CEM II has been used, whereas the content of fibers has been limited to about 1% in volume to maintain the workability of the mortars. To investigate the chemical compatibility, and the subsequent effects on the mechanical performances, prototypes have been tested in three point bending. After the mechanical test, the mortars microstructure was evaluated through SEM images and by thin section in transmitted light, in order to individuate a possible relationship between the dissolution of wool and curing conditions. The microstructure observation revealed the capability of wool fibers to bridge the cracks, and to reduce the brittleness of plain mortars. The differences in the mortars microstructure due to alternative curing conditions were also observed and described in the paper. Accordingly, wool could be effectively used to reduce the plastic shrinkage of cementbased composites, like the industrially manufactured polypropylene fibers.

Wool fibers, Plain cement-based mortar, Fiber-reinforced mortar, Polypropylene fibers, Three point bending tests, SEM analyses

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

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

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 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

In the paper the barite aggregate has been analyzed as a potential source of ASR in heavy concrete. Special attention was paid to BaSO4 and minor mineral components in aggregates and their influence on ASR development in tested mortars

heavy aggregate, Alkali Silica Reaction (ASR), ionizing radiation

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

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

kruszywa łamane, reakcja AAR, analiza petrograficzna