Correlation between different properties of recycled aggregate and recycled aggregate concrete

Abstract

The use of recycled aggregate (RA) in concrete has been increasing popularity over the last decades. Researches have been taken place in this field to develop information about strength properties of recycled aggregate concrete (RAC). In this research, three RA samples collected from different sources were used to produce different RAC mixes to investigate the correlation between RA and RAC properties. Two control mixes were made with two different water-to-cement (w/c) ratios (0.5 and 0.6). RA was placed in concrete by 0%, 50% and 100% to produce 12 different RAC mixes with the same w/c ratios used in the control mixes. During the mix deign it was focused on accurately compensating for the high-water absorption of RA to keep the effective w/c ratio constant for all concrete mixes. The main RA properties studied in this research were specific gravity, water absorption and porosity. The hardened properties investigated were the compressive strength, the flexural strength and the tensile strength. Typical relationships between RA properties and RAC characteristics were formulated. The results indicated strong correlation between RA properties and RAC characteristics. It should be highlighted that irrespective of RA source, all RAC mixes exhibit a very good workability similar to that of the normal concrete. The results also showed that adding extra quantities of water to the concrete mixes to compensate for the high-water absorption of RA will eliminate the effect of RA source on RAC properties since the strength properties of all RAC mixes were almost the same. It was concluded that the water absorption capacity of RA is the most important parameter that significantly affects RAC properties.