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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 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%).

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.