Instytut Podstawowych Problemów Techniki

Streszczenie:

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.

Słowa kluczowe:

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

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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.

Słowa kluczowe:

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

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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

Słowa kluczowe:

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

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During the wintertime, concrete pavements experience harsh exposure conditions due to the presence of both the freezing–thawing and wetting–drying cycles. Airport concrete pavements are commonly de-iced using chloride-free organic salts such as potassium formate or potassium acetate. However, these materials contain alkali ions which can have harmful effects on both the cement matrix and the aggregate. Specifically, there is an increased risk of occurrence of the alkali–silica reaction (ASR). The goal of this research was to estimate the influence of potassium formate on the potential of causing alkali–silica reaction in aggregates with different categories of reactivity (R0, R1, R2). The accelerated mortar bar test and its modification (which involves replacing sodium hydroxide solution with a potassium formate solution) were used. Detailed SEM-EDS examinations were performed to confirm the presence of alkali–silica reaction and to analyze the influence of potassium formate on the microstructure of mortar.

Słowa kluczowe:

alkali–silica reaction,potassium formate,de-icing agent,reactive aggregate

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Streszczenie:

Alkali-silica reaction (ASR) is a phenomenon that causes irreversible damage to concrete structures. Since 1940, research has continued to investigate the possibility of eliminating these negative effects. The lack of availability of non-reactive aggregates requires the use of reactive aggregates, characterized by satisfactory physical and mechanical properties, with the introduction of innovative solutions to mitigate the effects of ASR expansion. Recently, fibre-reinforcement has shown to be a promising approach, even if the type and the volume of fibres used to reduce, or eliminate, the deleterious effects of expansion are not well established. For this reason, Miniature Concrete Prism Tests (MCPT) were performed on 4 series of expansive concrete prisms without any fibres and with 0.5% in volume of polypropylene fibres, steel fibres, and recycled carbon fibres, respectively. In addition, 4 series of non-expansive mortar prisms, with and without fibres, were tested in bending. As a result, by using recycled carbon fibres a moderate expansion can be observed after 56 days, in contrast to the high expansion of un-reinforced concrete. The same positive effect cannot be observed in concrete reinforced with steel or polypropylene fibres. This is due to the absence of the deflection hardening capacity of the fibre-reinforcement, as confirmed by both mechanical tests on non-expansive mortars, and by the analysis of microstructure on the post-mortem specimens.

Słowa kluczowe:

Mortar, Concrete, Bending tests, Miniature Concrete Prism Tests (MCPT), Expansion Microstructure

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Streszczenie:

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.

Słowa kluczowe:

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

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Streszczenie:

Sand used as fine aggregate in concrete may, under unfavorable environmental conditions, cause alkali-silica reaction and the consequent deterioration of durability and functional properties of concrete. The aim of this work is to compare alkali-silica reactivity of 18 natural sands of various origin. The potential reactivity of sands was tested according to the procedures PB/1/18 and PB/3/18 established in the Technical Guidelines issued by the General Directorate for National Roads and Motorways. Mineral composition of aggregate was analyzed in order to identify reactive minerals. Mortar bar expansion tests and microscopic analyses of the products of alkali-silica reaction were performed. The research indicated that 6 (33%) out of 18 tested aggregates should be classified as “moderately reactive” and 12 (67%) aggregates should be classified as “non-reactive”. It was demonstrated that the origin of sand affects its susceptibility to alkali-silica reaction.

Słowa kluczowe:

alkali-silica gel, expansion, fine aggregate, reactive minerals, sand

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In recent years, the construction industry has developed an ecological direction, which aims to use natural materials. These materials can be both vegetable and animal origin. Building structures made of such semi-finised products are usualy light, non-destructive for environment, and in many cases made of recycled materials. Such an eco-building model often does not require energy inputs for production. It contributes to the development of energy-saving investments which meet the current technical requirements. These materials can perform an insolating function, like sheep's wool or cellulose, as well as construction or finishing function made of products like plywood, fibrous materials with an external gypsum or wooden panel or clay plaster with straw. Such products are perceived as healthy and cheap, and in many cases available locally. These solutions can have a significant impact in modern construction due to the increase in the prices of traditional construction products and energy savings during construction and investment use. The article aims to provide basic information about selected materials of natural origin and compare them in terms of hygrothermal research.

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Hemp-lime bio-composite (hempcrete) is a new building material consisting of two main constituents: hemp shiv and lime-based binder. Hemp shiv is a woody core of Cannabis Sativa plant obtained in decortication process and chopped into particles. Lime-based binder is a mix of binders with highest content of hydrated lime (other ingredients often present in a mix are: natural hydraulic lime, pozzolans, cement and others). Its natural origin, ability to crate healthy indoor environment, good thermal properties and especially high ecological values (including low carbon emission in the entire life-cycle) makes it an sustainable alternative to commonly used materials in construction industry. Due to its mechanical properties hempcrete is not a load-bearing material. It is used as a filling material for single-layer walls with a structural frame and as an insulation material for existing walls, floors and roofs. Construction techniques include forming monolithic walls by compacting the mix in a formwork, spraying, bricklaying from precast blocks and prefabrication of entire wall elements. In this paper the results of mechanical and hygrothermal properties of the developed hemp-lime composites will be presented. The results will be used to obtain the hygrothermal characteristics of the building partitions applying numerical simulation methods.

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The present paper reports on an innovative and simple route for the preparation of new hybrid materials based on TiO2 and carbonaceous supports with relatively high biochar content prepared via controlled laboratory batch pyrolysis system. Pine tar was used as a precursor for secondary char (confirmed by TGA) serving as a coating and “connecting material” between commercially available Degussa P25 TiO2 and biomass derived porous carbon support (biochar) produced from softwood or Lignin. The prepared hybrid materials were characterized by a series of physico-chemical characterization techniques such as XRD, XPS, TGA, UV–vis, XRF, SEM, COD and BET analysis. The results confirmed that the method used is viable and can be used to embed TiO2 in the structure of biochar. In aqueous phase phenol degradation, the TiO2/(secondary char-coated biochar) hybrid materials proved photocatalitically active, and especially the TiO2/secondary char-coated SWP700) showed better photocatalytic performance than the commercial TiO2 counterpart.

Słowa kluczowe:

Biochar,Lignin,Pyrolysis,Secondary char,Water detoxification

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Streszczenie:

We present a facile and green approach to produce crystalline TiO2 nanoparticles on a surface of different carbonaceous materials derived from lignocellulosic biomass such as STARBON-800® obtained by carbonization at 800 °C and biochar-SWP700 (Soft Wood Pellets (SWP) obtained by pyrolysis at 700 °C) via novel low-temperature ultrasound-promoted green methodology coupled with citric acid as a cross-linking agent. In comparison to other methods, the developed method has several significant benefits such as simplicity, great ability to get crystalline TiO2 particles (elimination of high-temperature treatment (material calcination at >300 °C) needed in the conventional sol-gel method, which is extremely important in transforming amorphous TiO2 into a photoactive crystalline phase) elimination of risky chemicals and oxidizing agent, and also ability to change some parameters (e. g. ultrasound intensity). Prepared materials were characterized by XRD, DR UV−vis, N2 physisorption, HR-XPS, XRF, HR-TEM, FT-IR and subsequently tested for their photocatalytic activities both in photocatalytic phenol degradation (in water) and oxidation of methanol (in air) under UV and visible light irradiation.

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Molybdenum trioxide-supported palladium catalyst Pd/MoO3(SPD) is prepared by the sonophotodeposition procedure (SPD). This method combining sonication with ultraviolet irradiation is used at room temperature and atmospheric pressure and does not require the use of chemical reducing agent. For comparison, the Pd/MoO3 catalysts are also prepared by the ultrasound irradiation and traditional impregnation - H2 reduction methods. The Pd/MoO3 catalysts are characterized by X-ray diffraction (XRD), electron microscopy (SEM, TEM, HRTEM), energy dispersive (EDS, STEM) analysis and X-ray photoelectron spectroscopy (XPS). The SPD treatment improves the platelets-like morphology of the MoO3 oxide grains making more difficult formation of hydrogen bronzes HXMoO3 (x > 0.9) studied by microcalorimetric method. The “in situ” reduction of precursor ions during the SPD treatment generates much better dispersed Pd-nanoclusters than other preparation methods. It results in much higher activity of Pd/MoO3(SPD) catalyst for the cinnamaldehyde hydrogenation than its MoO3-supported counterparts and Pd/SiO2, a reference catalyst.

Słowa kluczowe:

Palladium,Molybdenum trioxide,Sonophotodeposition,Cinnamaldehyde,Hydrogen bronze

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The present review paper highlights recent progress in the processing of potential municipal solid waste (MSW) derived fuels. These wastes come from the sieved fraction (∅ < 40 mm), which, after sorting, can differ in biodegradable fraction content ranging from 5–60%. The fuels obtained from these wastes possess volumetric energy densities in the range of 15.6–26.8 MJL−1 and are composed mainly of methanol, ethanol, butanol, and carboxylic acids. Although these waste streams are a cheap and abundant source (and decrease the fraction going to landfills), syngas produced from MSW contains various impurities such as organic compounds, nitrogen oxides, sulfur, and chlorine components. These limit its use for advanced electricity generation especially for heat and power generation units based on high temperature fuel cells such as solid oxide fuel cells (SOFC) or molten carbonate fuel cells (MCFC). In this paper, we review recent research developments in the continuous MSW processing for syngas production specifically concentrating on dry reforming and the catalytic sorbent effects on effluent and process efficiency. A particular emphasis is placed on waste derived biofuels, which are currently a primary candidate for a sustainable biofuel of tomorrow, catalysts/catalytic sorbents with decreased amounts of noble metals, their long term activity, and poison resistance, and novel nano-sorbent materials. In this review, future prospects for waste to fuels or chemicals and the needed research to further process technologies are discussed.

Słowa kluczowe:

Ni catalyst,MSW,gasification,dry reforming,HCl removal

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A series of new inorganic-organic hybrid materials based on TiO2 and new biochar-based supports (biochar obtained by pyrolysis of Miscanthus Straw Pellets (MSP) and Soft Wood Pellets (SWP) at 550 and 700 oC) were successfully prepared using ultrasound-assisted
methodology. The resulting composites were characterized by a wide range physicochemical techniques and investigated in water and gas phase photocatalytic test reaction. Our best composite (TiO2/SWP700) achieved phenol degradation of 64.1% (under UV light) and 33.6% (under visible light). In addition, it also showed an extraordinarily high activity (~90%) in selective oxidation of methanol to methyl formate in flow gas phase, high selectivity to
methyl formate (~80 %) and high yield of methyl formate (~88 %) after 240 minutes of illumination. It can be noticed that when TiO2 is supported on biochar, presented a superior photocatalytic ability and could be recycled at least 5 times in both photocatalytic runs tests with reproducible high photocatalytic efficiency.

Słowa kluczowe:

Biochar,TiO2,Synthesis of composite photocatalysts,Sonication for composite preparation,Phenol degradation,Methanol oxidation

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This review comprises the preparation, properties and heterogeneous photocatalytic applications of TiO2 immobilized on carbon materials derived from earth-abundant, renewable and biodegradable agricultural residues and sea food waste resources. The overview provides key scientific insights into widely used TiO2 supported on carbonaceous materials emanating from biopolymeric materials such as lignin, cellulose, cellulose acetate, bacterial cellulose, bamboo, wood, starch, chitosan and agricultural residues (biochar, charcoal, activated carbon and their magnetic forms, coal fly ash) or seafood wastes namely eggshell, clamshell and fish scales; materials that serve as a support/template for TiO2. Heightened awareness and future inspirational developments for the valorisation of various forms of carbonaceous functional materials is the main objective. This appraisal abridges various strategies available to upgrade renewable carbon-based feedstock via the generation of sustainable TiO2/carbon functional materials and provides remarks on their future prospects. Hopefully, this will stimulate the development of efficient and novel composite photocatalysts and engender the necessary knowledge base for further advancements in greener photocatalytic technologies.

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It has been demonstrated that sonophotodeposition can be one choice as a green method to synthesize bimetallic supported photocatalysts with enhanced performance for selective oxidations. A series of Pd–Cu supported on Titania-P90 photocatalysts were successfully prepared using this innovative method of effective synergistic combination of sonication and light. In addition, our method does not require the use of strong chemical reduction agent and it is executed in a short time, room temperature and atmospheric pressure. The prepared materials were characterized by a number of techniques such as High-Resolution Transmission Electron Microscopy (HRTEM), DR UV–vis spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and powder X-ray diffraction (XRD). Additionally, better bimetallic systems were obtained (methanol conversion >50% and selectivity to methyl formate >80%) by SonoPhotoDeposition (SPD) than in the case of the conventional photodeposition methodology. It has been discussed the possible reasons of the observed slight deactivation (8% after 2 h reaction test) of the best performing material in gas phase methanol selective photo-oxidation.

Słowa kluczowe:

Sonophotodeposition,Bimetallic,TiO2,Sonication,Methanol photo-oxidation

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In recent years, a good number of methods have become available for the preparation of an important group of photoactive materials for applications in photocatalysis and solar cells. Nevertheless, the benefits derived from preparing those materials through unconventional approaches are very attractive from the green chemistry point of view. This critical review work is focused on sonication as one of these promising new synthetic procedures that allow control over size, morphology, nanostructure and tuning of catalytic properties. Ultrasound-based procedures offer a facile, versatile synthetic tool for the preparation of light-activated materials often inaccessible through conventional methods.

Słowa kluczowe:

Photoactive materials by sonication,Photocatalysis,Ultrasounds,Solar cells,Perovskites,Quantum dots

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The aim of this work is to develop bimetallic Pd–Au/TiO2 P90 systems, which are highly active and selective for the photocatalytic oxidation of methanol to form methyl formate. Modification of commercial TiO2 P90 with Pd–Au nanoparticles was successfully achieved for the first time by means of a sonophotodeposition (SPD) method. The prepared materials were characterized by TEM, UV/Vis spectroscopy, X-ray photoelectron spectroscopy, and powder XRD. The Pd–Au bimetallic nanoparticles supported on titania exhibited remarkably enhanced catalytic activity in selective methanol oxidation to form methyl formate due to the synergism of Au and Pd particles, as well as the strong interaction between TiO2 and Pd–Au. SPD is a green methodology that can be used to prepare well-defined bimetallic surfaces on semiconductor supports with great promise for catalytic applications, in which selectivity can be tuned through adjustment of the surface composition.

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Carbonaceous N-containing materials derived from leather skin residues have been found to have unprecedented photocatalytic properties as compared to P25 Evonik, with an interesting degradation potential for contaminants in water (e.g. phenol). The carbonaceous materials were prepared by carbonization of the leather skin residues at different temperatures (180–600 °C). Different crystalline species of Cr2O3 and TiO2 were found in the materials obtained. In spite of a low surface area and phase crystallinity, a thermally treated material at 180 °C containing doped chromium oxides (eskolaite phase) provided remarkably improved activities with respect to classical titania derived materials.

Słowa kluczowe:

Leather skin residues,Photocatalysis,Chromium oxide,Phenol degradation

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The average size of the TiO2 nanoparticles was controlled at around 30 nm on Starbon 800 without using any surfactant, which is attributed to the hydrolysis and condensation (it is also proposed to be a plausible condensation with the carboxylate groups on the carbon surface) of the dissolved titanium(IV) isopropoxide into TiO2 by ultrasonic waves. As the Starbon in the composites has very good contact with the TiO2 nanoparticles (there is no Ti leaching after 240 min of photocatalysis, XRF analysis) it enhances the photo-electron conversion (better than Norit and graphene oxide carbons) of TiO2 by reducing the recombination of photo-generated electron–hole pairs. We have prepared an excellent new hybrid photocatalyst for aqueous phase phenol total mineralization.

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