Study of pavement quality concrete mix incorporating beneficiated recycled concrete aggregates

The present study is an effort to investigate the influence of recycled concrete aggregates (RCAs) on the mechanical and durability properties of pavement quality concrete under different moisture states. Four moisture states, namely as received state (AD), saturated surface dry state (SSD), fully saturated state (FSD) and oven dried state (OD) of aggregates were considered in this study. RCAs manufactured upon processing of demolished concrete wastes were subjected to chemical beneficiation (using H2SO4) followed by abrasion prior to their incorporation in an experimental programme. In all, 24 mixes incorporating RCAs at different proportions of 10–50% with an interval of 10% for M-40 grade of concrete were prepared to investigate the properties of hardened concrete, such as compressive strength, flexural strength, water absorptions, chloride ion concentrations, sorptivity, abrasion, etc. Scanning electron microscopic analysis on thin samples collected from all 24 mixes was carried out in order to understand the surface morphology of concretes. The strength parameters of concrete mixes were found to be decreasing with increase in incorporation levels of RCAs in accordance with past studies. Among the mixes prepared with different moisture state of aggregates, SSD mixes were found to have better strength parameters, while those prepared using the FSD moisture state of aggregates showed the lowest values. The test results from chloride ion concentration and sorptivity indicate that mixes with RCA content up to 30% had test values within the specified limits, thus suggesting their potential use for pavement quality concrete.