Compounding effect and an expanded theoretical model for recycled coarse and fine aggregate concretes under uniaxial loading

This paper aimed to experimentally investigate how the influence of fine recycled aggregate (FRA) replacement ratio (r(F), varies from 0% to 100%) on the compressive stress-strain behavior of recycled aggregate concrete (RAC) varies with the coarse recycled aggregate (CRA) replacement ratio (r(C), varies from 0% to 100%), i.e., the compounding effect between FRA and CRA. The influence of recycled aggregate (RA) on the development of dilation ratio (epsilon(h)/epsilon(v), the ratio of transverse to longitudinal strain) was also investigated. Two series of tests were conducted to confirm the compounding effect in RAC. Test results showed that the FRA and CRA had a considerable compounding effect on the compressive strength (f(c)), deformability (epsilon(u)/epsilon(0), the ratio of ultimate strain to strain at the maximum stress) and dilation ratio (epsilon(h)/epsilon(v)), while this effect was insignificant on the strain at the maximum stress (epsilon(0)). Based on the crack band theory by Bazant (1984) and two-phase composite material theory, an expanded theoretical model was proposed to predict the stress-strain relationship of RAC. The model was then benchmarked against totally 81 groups of specimens with a wide range of concrete strengths and treatment methods of FRA and CRA.