Shear Transfer Strength of Concrete After Exposure to Elevated Temperature

Abstract

The most consumed construction material in the world, concrete, is largely composed of coarse aggregate. Thus, the physical and mechanical properties of aggregates play a significant role in determining the performance of concrete. Nowadays, recycled concrete aggregate (RCA) is increasingly replacing natural aggregate to reduce the pressure on natural quarries and to minimize the demolition of waste and create resource recovery. Most research studies have been conducted on the mechanical behaviour of RCA concrete made with full or partial replacement with RCA. However, the shear strength of RCA concrete at or after exposure to high temperature has not been studied extensively. Thus, more knowledge regarding the residual strength after exposure to high temperature will provide important information to assess the capacity of concrete structures after fire exposure. This thesis examines the residual shear strength of concrete made with different types of coarse aggregate after exposure to elevated temperature. In total, 48 initially un-cracked push-off specimens were prepared from six concrete mixes (round river gravel, Kingston red granite, crushed limestone, and RCA concrete with three RCA replacement ratios (30%, 70%, and 100%)). Half of the specimens were tested at ambient temperature (22±2oC) and the remainder were tested after heating to 500oC. In addition to linear potentiometer (LP) measurements for the shear slip and crack width at the middle of the specimen, digital image correlation (DIC) techniques were performed to observe the field level shear displacement. Eighty-eight cylinders were prepared to observe the compressive and splitting tensile strength on the same test regime. The shear transfer strength of concrete was found to be independent on the type of coarse aggregate for both heated and unheated specimens. RCA concrete has comparable compressive, splitting tensile and shear transfer strength compared to similar concrete made with other types of natural coarse aggregate. The reduction in residual shear transfer strength of the concrete is more severe than the reductions in compression and splitting tensile strength of the concrete. Greater load versus crack width and slip responses were recorded for heated specimens compared to their unheated counterpart specimens.