Creep behaviour of concrete using recycled coarse aggregates obtained from source concrete with different strengths

Available creep models for recycled aggregate concrete (RAC) only consider the effect of residual mortar content (C_RM). This paper highlighted how the creep of RAC was also influenced by the property of the residual mortar which highly depended on the water-to-cement ratio of the source concrete (w_or/c_or) and how the increase in creep which was induced by the recycled coarse aggregate (RCA) varied with the water-to-cement ratio of the resulting concrete (w/c). Forty RAC specimens with the w_or/c_or ratios and the w/c ratios varying between 0.3 and 0.6 were prepared and tested up to 8 months. It was found that the influence of the RCA on the creep deformation of RAC was more pronounced for RAC with lower value of w/c or using RCA from source concrete with higher w_or/c_or ratio. Finally, a ‘water-to-cement ratio factor’ was introduced to the available creep model to account for these influences. Benchmarking analysis against available experimental data indicated that, the newly proposed model had better accuracy in predicting creep of RAC, especially for RAC with aggregates obtained from high-strength concrete.