Time-dependent drying shrinkage model for concrete with coarse and fine recycled aggregate

This study aims to develop a drying shrinkage model for recycled aggregate concrete (RAC) using both fine and coarse recycled aggregate (termed FRA and CRA, respectively). An experiment was conducted to measure the drying shrinkage of RAC with varying replacement ratios of CRA (0%, 50%, and 100%) and two types of FRAs (0%, 50%, and 100%). Test results show that: (1) both FRA and CRA have significant influence on the development of drying shrinkage, (2) the influence of FRA on the development of drying shrinkage decreases with increasing content of CRA, and (3) the influence of FRA on the final drying shrinkage is almost independent of the CRA. For example, the use of 100% FRA results in an increase of 23%-41% for concrete with 0% CRA. Similarly, 100% FRA results in 29%-38% increase for concrete with 100% CRA. Based on the results, a new model with two influence factors is proposed accounting for the influence of recycled aggregate on the development of drying shrinkage and on the final value of drying shrinkage of RAC; the expression was validated using a database of RAC shrinkage test data.