Influence of service time of recycled coarse aggregate on the mechanical properties of recycled aggregate concrete

Abstract

The mechanical properties of recycled aggregate concrete (RAC) may be affected by the service time of parent concrete used to produce the recycled coarse aggregate (RCA), which has not been experimentally investigated. Current models primarily relate RAC elastic modulus to its compressive strength. These models cannot describe the difference in the mechanisms of the influence of the incorporation of RCA on the concrete elastic modulus and that on the concrete strength. This paper first investigated how the compressive strength, static modulus of elasticity and shrinkage deformation of the RAC are influenced by the service time of the RCA (1, 18 and 40 years). The RCA was adopted as 0%, 30%, 50% and 100% replacement of the natural coarse aggregate. Based on two-phase composite material theory, the elastic modulus model was then developed for RAC which is related to the elastic modulus of the companion natural aggregate concrete by accounting for the influence of residual mortar content (CRM) to achieve a better accuracy in wider parameter ranges. The model to predict the development of the compressive strength over time was also proposed for the RAC by modifying the EC2 model. Results obtained indicated that RAC compressive strength was affected by the service time of the parent concrete, and the newly proposed models showed good accuracy in predicting RAC mechanical properties.