The article examines the features of dismantled paving slabs as raw materials for the production of recycled aggregate for concrete. The effect of crushed fine fractions of secondary crushed stone screenings on the properties of fine-grained self-compacting concrete was investigated. It was experimentally shown that the use of this material as a mineral additive leads to an increase in the water demand of the self-compacting fine-grained mixture and a significant decrease in strength.

Keywords: demolition waste, vibro-pressed paving slabs, recycling, screening of secondary crushed stone, mineral additive, self-compacting fine-grained concrete, consistency of concrete mix, strength, shrinkage

The influence of secondary crushed stone on the strength and shrinkage of concrete was studied. The results showed that when granite coarse aggregate is replaced with crushed recycled concrete, the compressive strength of concrete is reduced by an average of 20% and the flexural strength by 3-10%. Concrete on recycled crushed stone has a high shrinkage. The shrinkage of concrete with a minimum consumption of recycled aggregate differs slightly from the shrinkage of concrete on granite crushed stone.

Keywords: demolition waste, concrete scrap, recycling, recycled aggregate, compressive strength, flexural strength, shrinkage

The results of research on the effectiveness of a multistage crushing of concrete scrap by the "soft" regime are given. It was found that the processing of concrete scrap by this technology can significantly improve some properties of recycled concrete aggregate, particularly crushability, water absorption, shape factor "average thickness of the grain" and porosity. The result of this treatment is the formation of a significant amount of particulate material. This material can be used as a fine filler in the technology of self-compacting concrete. It was found that self-compacting concrete based on products of crushing concrete scrap has a strength of 50 MPa after 28 days of curing in normal conditions, and more than 70 MPa after one year of storage in dry-air conditions. It was established that received concrete has a lower modulus of elasticity, which should be considered when choosing the fields of its application.

Keywords: self-compacting concrete, concrete scrap, secondary aggregates, multi-stage crushing, crushability, water absorption, elastic modulus