Performance Evaluation of Construction and Demolition Waste Materials for Pavement Construction in Egypt

This paper focuses on the feasibility of using construction and demolition (C&D) waste materials, particularly blends of recycled concrete aggregate (RCA) with recycled clay masonry (RCM), as unbound granular materials (UGMs) for road construction in Egypt. The proportions of the RCA/RCM blends were $100/0$, $90/10$, $80/20$, $70/30$, $55/45$, $40/60$, $20/80$, and $0/100\%$ of the total aggregate mass. In addition to the index properties of the blends, the samples of RCA and RCM before and after mixing were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The initial matric suction was measured for the selected blends. Static triaxial shear and repeated load triaxial tests (RLTT) were conducted on triplicate specimens prepared according to the modified Proctor optimum moisture content and maximum dry density. Results showed that the initial matric suction increased by decreasing the RCM at a given moisture content. The RLTT results showed that as the RCM increased, the resilient modulus generally decreased. The universal resilient modulus (${\mathrm{M}}_{\mathrm{r}}$) model was modified by incorporating the content of the RCM to predict the resilient modulus for the RCA/RCM blends. The proposed model yielded accurate predictions with the $R^2$ of 0.82. Finally, the pavement performance in terms of rutting and fatigue cracking was estimated using multilayer elastic analysis along with the mechanistic-empirical pavement design guide (MEPDG) performance models and transfer functions. The predicted pavement performance of the sections with recycled materials as the subbase/base layers was better than the sections constructed with the typical virgin aggregate.