Drying shrinkage model for recycled aggregate concrete accounting for the influence of parent concrete

Abstract The drying shrinkage of recycled aggregate concrete (RAC) varies considerably owing to the extensive sources of parent concrete from which recycled aggregates are obtained. This paper proposes a theoretical drying shrinkage model for RAC considering the properties of the parent concrete, including its service time and strength. To achieve this, shrinkage tests were conducted on 60 concrete specimens over 360 days. Five types of parent concrete with different service times (1 year, 20 years, and 42 years) and water-to-cement ratios (0.30, 0.45, and 0.60) were crushed to obtain recycled coarse aggregates (RCAs) that were used to prepare the RAC specimens. Three RCA replacement ratios (0%, 50%, and 100%) and three RAC water-to-cement ratios (0.30, 0.45, and 0.60) were assessed. The results indicated that the drying shrinkage of RAC was effectively reduced by an increase in the parent concrete strengths and vice versa. A theoretical RAC shrinkage model was developed considering the influence of the residual mortar content and parent concrete strength. A benchmarking analysis using 262 shrinkage samples demonstrated that the proposed model offers improved accuracy for estimating the long-term drying shrinkage of RAC over existing methods, particularly when the parent concrete and RAC have large strength variations.