Дослідження модифікації зерен рециркульованого заповнювача алюмосилікатними покриттями

This study investigates the possibility of improving the efficiency of using recycled coarse aggregate obtained from waste concrete structures by modifying its surface with aluminosilicate coatings based on alkaline binders. Modern approaches to improving the properties of recycled aggregates are considered, among which the formation of a mineral coating on the grain surface is identified as the most promising. Particular attention is paid to the use of an alkaline aluminosilicate binder system Na₂O–Al₂O₃ –SiO₂–H₂O, which, thanks to its high adhesive properties, strengthens the aggregate’s surface layer, seals microcracks, and binds cement dust and residues of old cement paste. As a result, a new high-quality interface zone is formed between the cement matrix and the aggregate (ITZ zone), which contributes to improved concrete performance. A comparative assessment of the quality of recycled aggregate obtained by various crushing methods was conducted. It was found that commercial recycled crushed stone exhibits the lowest strength and crack resistance values, which justifies its further modification. The influence of process and formulation factors on the performance of an aluminosilicate coating was investigated. The duration of mixing the filler with the binder, the coating curing temperature, the type of metakaolin, and the number of water molecules in the binder were varied. It was established that the optimal conditions are mixing for 5 minutes and heat treatment at 100 °C for 2 hours. The best results in terms of reducing water absorption were achieved with a water content of n=12; however, from a technological standpoint, the most rational composition is n=15, which provides a balance between processability and performance characteristics. The results obtained confirmed the fundamental possibility of improving the properties of recycled aggregate through the use of aluminosilicate coatings with directed synthesis of hydrates of the mixed system Na₂O–CaO–SiO₂–Al₂O₃–H₂O. The proposed approach contributes to improving the durability and strength of concrete with recycled aggregate and represents a promising direction for the development of resource-efficient technologies in construction