Shrinkage behavior of recycled lump/aggregate concrete containing recycled sand from weathered residual soil of granite

Abstract

The simultaneous use of demolished concrete lumps, recycled coarse aggregates (RCAs), and recycled sand (RS) from weathered residual soil of granite in concrete can significantly improve the recycling of construction and demolition waste, but the effects of the aforementioned three waste materials on the shrinkage behavior of concrete remain unknown. In this study, autogenous and total shrinkage tests were conducted on recycled lump/aggregate concrete (RLAC). The effects of the RS replacement ratio, RCAs, demolished concrete lumps, and MgO expansion agent on the autogenous and drying shrinkage were investigated comprehensively. The results showed that: (a) at the age of 188 days, the autogenous and drying shrinkage of RLAC with 50% RCAs increased with an increase in the RS replacement ratio; (b) at 188 days, the autogenous and drying shrinkage of RLAC with 50% RS decreased and increased, respectively, with the adoption of 50% RCAs; (c) the autogenous and drying shrinkage of RLAC could be decreased to a certain extent using demolished concrete lumps only or MgO expansion agent only; (d) after the use of demolished concrete lumps and MgO expansion agent, the autogenous and drying shrinkage of RLAC with 50% RCAs and 30%–70% RS at 188 days were lower and higher (12.9%–29.9% higher) than that of natural aggregate concrete, respectively. Finally, predictive models were developed to determine the autogenous and drying shrinkage of RLAC.