Properties of recycled coarse aggregates obtained from crushed concrete waste

Abstract

According to the Kyiv School of Economics as of January 2024, the losses from the destruction and damage of buildings and structures as a result of military actions in Ukraine amount to at least 75 billion dollars. Now contractors carrying out the liquidation of the consequences of armed aggression are required to take measures to reuse construction waste. Taking into account the presence of natural crushed stone in concrete scrap, the question arises about the possibility of using crushed concrete in new construction. During the design a concrete mixture it is necessary to know such characteristics of aggregates as grain size composition, bulk density, specific density, voids, strength.Three mixtures of concrete were designed and aseries of cube samples were made from them to determine the specified characteristics of recycledcoarse aggregate obtained from crushed concrete on local materials. At the appropriate age the samples of origin concrete were crushed using a laboratory jaw crusher.The results of sieve analyses showed that ungraded mixtures of fine and coarse fractions do not meet the requirements of national standard due to the large content of coarse fractions. At the same time, in general, the granulometric composition of only coarse fractions meets the requirements of standards in Ukraine. The obtained bulk densities and specific densities differ in different fractions with a large dispersion even within the same fraction. The strength of the aggregate decreases with a decrease in grain sizes. Thus, the main factor that has a decisive influence on the properties of RCA and concrete with their use is the presence of residual mortar. The smaller the fraction of the RCA, the higher the residual mortar content, up to individual grains that are entirely composed of it. Therefore, one of the methods of improving the properties of RCA is to reduce the content of the residual mortar.