Resilient and permanent deformation behaviors of construction and demolition wastes in unbound pavement base and subbase applications

Abstract The reuse of construction and demolition wastes (C&D wastes) as unbound granular materials (UGMs) to construct pavement base and subbase courses is of great potential, while the cyclic behaviors of unbound C&D wastes under traffic loadings still lack the support of test data. To investigate the traffic-induced resilient and permanent deformation behaviors as well as the shear and particle breakage properties of the unbound recycled concrete aggregate (RCA) & recycled clay masonry (RCM) blends, a series of consolidated drained, resilient deformation and permanent deformation tests by a large-scale dynamic triaxial apparatus were performed. The RCM content in two blends made by different mixed methods was emphasized, and the factors of gradation, confining pressure and cyclic deviatoric stress amplitude were also taken into consideration. Test results show that RCM content makes great influences on the particle breakage, resilient modulus, permanent axial strain and shakedown behavior of unbound RCA & RCM blends, and the influences show obvious differences between the two mixed methods. The peak triaxial strength, particle breakage level and resilient modulus of blends 1 (B1) are generally larger than those of blends 2 (B2), and the influence of confining pressure and cyclic deviatoric stress amplitude on resilient modulus are related to the mixed method but unrelated to RCM content. The popular modified K-θ model is employed to predict Mr of B1 and B2, and the reference ranges of the regression coefficients with respect to RCM content are obtained. Based on the results, it is evaluated that when RCM content is below a certain extent (e.g. 30%), B1 perform better (and the best at around RCM content of 10%) as pavement base and subbase courses in regard to shear strength, resilient modulus and permanent strain. However, as the RCM content continues to increase, B2 may be better than B1 considering the overall performance of cyclic properties.