Properties of concrete containing recycled construction and demolition wastes as coarse aggregates

Abstract

The incorporation of mixed construction and demolition (C&D) wastes as a substitute to natural aggregates (NA) has many economic and environmental benefits. In this paper, the results of an investigation on the effect of recycled coarse aggregate (RCA) obtained from C&D wastes on mechanical and durability properties of concretes are presented and compared with concrete containing NA. Compressive, tensile, and flexural strengths are measured as part of mechanical properties and drying shrinkage, chloride ion permeability, water absorption, and sorptivity are measured as part of durability properties. The recycled aggregate concretes contain 25 and 50% RCA as replacement of NA. All samples are tested after 7, 28, 56, and 91 days of wet curing. The results show that the compressive strength of recycled aggregate concretes decreased with increase in RCA contents, however it improved with longer curing. Similar results are also observed in flexural and tensile strength of recycled aggregate concretes. The drying shrinkage of recycled aggregate concretes also increases with increase in RCA contents and time to drying exposure until 56 days. However, the rate becomes constant after 56 days of drying. The recycled aggregate concretes also exhibit poor sorptivity, water absorption, and chloride ion permeability compared to concrete containing NA. The result of poor durability performance of recycled aggregate concretes is relative to high porosity of constituents and interconnectivity of the pore system in the concrete. Correlations between different durability properties and compressive strength of recycles aggregate concretes are also established in this study.