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This paper describes research on the synergistic effect of nano–SiO2 (NS) and spent fluid catalytic cracking catalyst (FCCCw) in cement pastes’ pozzolanicity. Binary and ternary blended cement pastes containing 0.02% of NS and 5–20% of FCCCw were investigated. Hydration at early age followed using semi-adiabatic calorimetry. The macroscale properties were assessed by measuring density, ultrasonic pulse velocity and compressive strength. The microstructures were analysed by scanning electron microscopy, X-ray diffraction and thermogravimetric analysis. The results are consistent among the different techniques and materials’ levels and show that a small NS content promotes a marked synergistic enhancement of the pozzolanic reaction.

The aim of work is to determine the lowest and effective amount of nano SiO2 (NS) for cementitious paste and identify the complex impact of NS and chemical admixtures on cement hydration and physical-mechanical properties. In order to achieve the aim, cementitious specimens with different types and amounts of NS were formed. Further, after the selection of NS and its amount, specimens were formed with various superplasticizers. The work analysis the following properties of cementitious mixtures and hardened cement stone: flow diameter, exothermal temperature, density, ultrasound pulse velocity, compressive strength, microstructure and mineralogical composition. It was determined that the greatest strength of cementitious specimens was obtained when 0.02 wt.% of NS was used, and, compared to control specimens, it increased by ∼15%. Additionally, the greatest increment in strength was observed for specimens with melamine-based superplasticizer. Compared to control specimens, the strength increased up to 23% and the obtained density and ultrasound pulse velocity were the greatest. XRD analysis showed that all specimens had analogue crystal hydrates formed but their amounts are different. SEM analysis showed that structure of the specimens with NS is denser.

The article analysis the application possibility of plastic waste and their impact on the properties of expanded clay concrete. Two plastic waste are selected from SC “Plasta” (A and B types). A type waste has slimy and dense structure, B is more porous and has rough surface. Whereas the average size of waste is up to 1 cm and the bulk density is similar to that of expanded clay, these waste have replaced a part of expanded clay with the fraction of 4/8 (0%, 5%, 10%, 20%) in expanded clay concrete mixtures. Amounts of cement, fine aggregate (sand), 8/16 fraction expanded clay, water and superplasticizer in expanded clay concrete mixtures are constant. Properties of expanded clay concrete are determined and analysed as follows: density and slump of the mixture, density of the dried expanded clay concrete specimens, capillary rate, water absorption and compressive strength. Additionally, microstructure research is conducted. It is determined that using more waste (20%), by 4% denser and by 50% stronger expanded clay concrete may be obtained compared to the control specimens. To obtain expanded clay concrete with optimal properties, it is suggested to use 5% of A type waste instead of calculated amount of 4/8 fraction expanded clay. Then, the density of expanded clay concrete increases by 5% and it is equal to 1260 kg/m3, and compressive strength is by approximately 70% greater than the one of the control specimens and it is equal to 17 MPa. Moreover, the capillary rate and water absorption decrease. When up to 10% of A type waste are used, mixture slump increases and workability improves, therefore, the obtained specimens are easy to form. Microstructure analysis shows that there is sufficient adhesion between aggregates, waste and cement stone. The microstructure of cement stone under different loadings of waste is different. The densest structure has specimens with 5% of A type waste. The same minerals, i.e. portlandite, ettringite, calcite and calcium hydro silicates are determined in specimens from all batches. After conducting statistical analysis of the obtained compressive strength results, mathematical second degree polynomial dependence is concluded. It allows prediction of expanded clay concrete’s compressive strength depending on the amount of waste. Determination coefficient of the equation is equal to 0.845. It can be seen from the obtained equation that the compressive strength of expanded clay concrete increases under a certain amount of waste and then, it decreases.

The influence of technogenic waste (burned and unburned mullite wool) on the properties of cement concrete as well as the influence of unburned mullite wool on the properties of ceramics are analysed in the paper. For the purpose of research, the part of sand in a cement concrete (2%, 4%, 6%, 8%, 10%) was replaced by a mullite wool waste. When 10% of the burned mullite wool waste was used the compressive strength of concrete increased by 7.7% after 7 days, and by 3.2% after 28 days. When 8% of the unburned mullite wool waste was used the compressive strength of concrete decreased by 3.4% after 7 days, and by 12.2% after 28 days. The ceramic samples were made from 4 different formation mixtures, in which the amount of unburned mullite wool waste was 0%, 5%, 10% and 15% (the amounts of quartz sand were replaced with waste). The samples were burned at the temperatures of 1050 °C and 1080 °C, keeping them at these temperatures for 4 h. The experimental results showed that the application of mullite wool waste in the manufacture of ceramic products is beneficial because of its positive impact on ceramic properties and the possibility to avoid overloading landfill sites. At the optimum burning temperature of 1080 °C, the significantly higher frost resistance, compressive strength and lower water absorption of ceramics is obtained., The authors gratefully acknowledge the help of the VGTU Civil Engineering Centre in providing the laboratory equipment, which was used in the present investigation.

This paper is aimed to show the impact of bitumen roofing production waste (BTw) on the properties of cement mortars in terms of mineral composition, microstructure, setting rate, physical and mechanical properties and durability (water absorption, freeze-thaw resistance). To this aim, mortar specimens were manufactured by replacing 0%, 2%, 4%, and 6% of natural sand by weight with BTw. The main results show that BTw slightly accelerates cement hydration and 4% is the best content of BTw to be valorised in mortars. In this case, compressive strength, density and ultrasound pulse velocity are comparable to the control mortar (0% BTw content) but capillary water absorption decreases and flexural strength increases. Moreover, at this dosage, the forecasted freeze-thaw resistance of mortars increases considerably (~30%).

This article presents how concrete properties would change if part of a coarse aggregate (granite crushed stone) were replaced with bitumen roofing production waste (BTw). BTw is a huge ecological problem because these wastes are generated in large quantities when replacing old bitumen-based roof tiles. Wastes are also produced during the production of bituminous roof coatings. Usually BTw are stored in landfills or it is attempted to use/dispose them in the production of asphalt concrete. There are very few works which analyse the impact of BTw on the properties of cement materials, although the impact of these wastes on the properties of cement materials could be beneficial because BTw consist of aggregate, granules, bitumen and fibers. In order to use BTw, standard concrete samples were first formed, then 5/16 granite fraction was replaced with BTw in amounts of 2%, 4% and 6% by weight The amounts of limestone Portland cement, fine aggregate (sand), water and superplasticizer in the concrete mixtures were constant. The new generation of superplasticizer based on polycarboxylates was used in mixtures. The following concrete properties were identified and analyzed: density of the mixture, flowability, density of concrete samples, water absorption, compressive strength, forecasted frost resistance, and microstructure studies were conducted as well. The results of the studies showed that BTw can be used in small amounts, i. e. up to 6%, then the density of the samples slightly decreased (by 2.4%) and water absorption increased (by 0.7%). Compressive strength, after replacing 2% granite crushed stone, decreased by 2.4%. However, gradual addition of the amount of BTw resulted in more closed pores that improved the frost resistance of the concrete. When 6% of bulk filler was replaced with BTw, closed porosity, compared to control samples, increased by 54% and forecasted frost resistance - by 26%. Microstructure analysis showed that with 6% BTw a dense cement stone structure was formed, showing the hydrates of portlandite and CSH.

The properties of the hardened concrete depend on the selected raw materials: size and amount of the particles of coarse aggregate, as well as on the ratio of other components. Particular countries use various methodologies for the selection of concrete composition to select the components of the concrete mixture. However, the properties of the concrete, selected by using any methodology for the selection of the concrete composition and hardened by following the defined conditions, must satisfy the values of certain necessary characteristics. The results of the implemented research indicate that the most optimal solution is to use the coarse aggregate of multi‐fractional or discontinuous fractional composition. The optimal composition of the concrete must be selected to ensure that the binding material is not overdosed. Yet, all components must be selected in such a way, that the required properties of the final product are retained after concrete mixture hardens. When catalyst waste materials from the reactor of the catalytic cracking (15%) are used for the lightweight concrete, the density of the expanded‐clay lightweight concrete investigated and compressive strength increases even for the higher water/cement ratio, more heat is dissipated during the hydration of the cement and this exothermic effect occurs several hours earlier. Santrauka Sukietėjusio betono savybės priklauso nuo betonui parinktų žaliavų: stambaus užpildo dalelių dydžio ir jų kiekio, taip pat nuo kitų sudedamųjų dalių santykio. Betono mišinio sudedamąsias dalis šalys parenka įvairiais betono sudėties parinkimo metodais, tačiau pagal bet kurį betono sudėties parinkimo metodą parinkto ir pagal nustatytas sąlygas sukietinto betono savybės turi tenkinti tam tikrų būtinųjų charakteristikų vertes. Darbe atliktų tyrimų rezultatai parodė, kad optimaliu naudoti daugiafrakcį arba trūkiosios frakcinės sudėties stambųjį užpildą. Betono sudėtis turi būti parinkta nepereikvojant rišamosios medžiagos, tačiau visas sudedamąsias dalis parenkant taip, kad, sukietėjus betono mišiniui, išliktų reikiamos galutinio produkto savybės. Lengviesiems betonams naudojant katalizatoriaus atlieką iš katalitinio krekingo reaktoriaus (15 %), padidėja tiriamojo keramzitbetonio tankis, gniuždomasis stipris net esant didesniam V/C santykiui, o hidratuojantis cementui, išsiskiria daugiau šilumos, ir šis egzoterminis efektas įvyksta keliomis valandomis anksčiau. First Published Online: 14 Oct 2010 Reikšminiai žodžiai: betonas, užpildai, keramzitas, struktūriniai rodikliai, katalizatorius, egzotermijos temperatūra.