Experimental investigation of the performance of ground granulated blast furnace slag blended recycled aggregate concrete exposed to elevated temperatures

Abstract

This study focused on investigating the residual mechanical properties of ground granulated blast furnace slag blended recycled aggregate concrete (GGBS-RAC) after exposure to elevated temperatures. The residual compressive strength, splitting tensile strength, elastic modulus, and stress strain behavior of the GGBS-RAC were evaluated through laboratory experimental tests. The experimental phase includes material characterization for ground granulated blast furnace slag (GGBS) and recycled concrete aggregates (RCA) to determine their physical characteristic and chemical composition. GGBS was used to partially replace cement at four levels of 0 %, 20 %, 40 %, and 60 % while the water to binder ratio was fixed at 0.5. The targeted mechanical strength properties of GGBS blended RAC were analysed at both room temperature (about 25 ℃) and after exposure to elevated temperatures of 200, 400, 600, and 800 ℃. Scanning electron microscope (SEM) analyses were conducted to study the degradation mechanism of GGBS blended recycled aggregate concrete at room temperature and after exposure to elevated temperatures. The resistance to deterioration of residual mechanical strength in GGBS-RAC was found to be significantly enhanced compared to recycled aggregate concrete without GGBS, and better residual strength performance of RAC was observed at 40 % GGBS content. The microstructure images revealed that micro/macro cracks formation, as well as the decomposition of hydrated products in recycled aggregate concrete at high temperatures, are the main reasons for the reduction of mechanical strength properties after exposure to elevated temperatures.