Study of physical-mechanical properties of concretes based on recycled aggregates

The use of hybrid alkaline cements is effective for materials of general construction and special purpose, namely in the production of concrete mixtures and concretes based on them with an increased risk of structural loosening due to an increased content of organic residues and combustion products. Materials based on them are able to withstand the significant impact of swelling-shrinking deformations caused by the presence of combustion products and organic residues. This makes it possible to predict the effectiveness of their introduction to control the processes of concrete structure formation based on recycled aggregates. It is shown that the use of recycled aggregate in the composition of a concrete mixture based on alkaline cements makes it possible to obtain concrete mixtures of different mobility and concretes based on them, which according to their physical and mechanical properties meet the requirements for concrete for general construction purposes. Thus, recipes for concrete with an average density of 2200...2420 were developed kg/m3 and compressive strength at the age of 28 days at the level of 15.1...39.8 MPa at mobility of concrete mixture P2. The strength at the initial and middle terms of hardening (2 days and 7 days) also corresponds to the generally accepted indicators of the set strength of concrete of different classes. At the same time, the water-cement ratio of the studied concretes is characterized by sufficiently high indicators and varies at the level of 0.5...0.8, which is often unacceptable according to regulatory documents for concretes for general construction purposes, potentially creating problems with the long-term properties and durability of such concretes. Solving the mentioned problems is possible due to the selection of the composition of concrete mixtures by modifying them with additives of different origin and functionality.