Influence of recycled concrete aggregates on alkali-activated slag mortar exposed to elevated temperatures

Abstract In this paper, the residual compressive strength behavior and the features of the alkali-activated slag (AAS) mortar made with five different replacement ratios of recycled concrete aggregates (RCA), i.e. 0, 25, 50, 75, and 100%, were investigated after being exposed to the target temperatures of 23, 200, 400, 600, and 800 °C. For this purpose, after exposure to elevated temperatures, the compressive strength and the mass loss were determined. Petrographic image analysis and scanning electron microscopy (SEM) were also used to analyze the microstructures of the specimens. The results showed that utilizing 25% RCA in the AAS mortar improved its performance at ambient and high temperatures. In addition, stronger aggregate-paste bonding was observed between RCA and AAS paste at high temperatures in the petrographic images. Overall, using these two kinds of materials (slag and RCA) seems to have a great potential for boosting the cleaner production of sustainable, environmentally friendly green mortar.