Mechanical strength and durability properties of concrete containing treated recycled concrete aggregates under different curing conditions

This paper examines the mechanical and durability properties of concrete incorporated with treated recycled concrete aggregate (RCA) under different curing conditions. Three different curing regimes were applied, namely, continuous normal water curing (NW), initial water curing for 28 days before exposure to an open air environment (OA), and initial water curing for 28 days before exposure to seawater (SW). Two concrete mixes were produced by replacing 60% of the coarse aggregate using treated and untreated RCA with one control specimen (100% natural coarse aggregate) to examine the mechanical strength (compressive and flexural strength) and durability (water absorption, oxygen permeability, and also porosity) properties of the concrete. Meanwhile, the microstructure of these mixes was studied via scanning electron microscopy (SEM). The inclusion of untreated RCA generally reduces the mechanical strength and durability of the concrete regardless of the curing conditions. The compressive strength of the concrete containing untreated RCA is more detrimental in SW than in the other two curing conditions. Moreover, the concrete with RCA have poor intrinsic air permeability and porosity because their intrinsic porosity and effect are more significant when the curing is performed in OA than in the other curing conditions. Incorporating the treated RCA helps limit the reduction in the mechanical strength and durability of the concrete particularly under a prolonged curing period.