Effect of elevated temperature on the mechanical properties of high-volume GGBS concrete

Abstract

The aim of this study was to investigate the mechanical properties of fire-damaged concrete containing a high volume of ground granulated blastfurnace slag (GGBS). Concrete specimens were cooled by water spraying, as is usual for extinguishing a real fire. In this research, GGBS was used at 0%, 50%, 60% and 70% replacement by weight of cement. The high-volume GGBS concrete specimens were subjected to seven different elevated temperatures from 20°C to 700°C. After being water-cooled to room temperature, the compressive strength, splitting tensile strength and modulus of elasticity of the concrete specimens were determined. Additionally, the loss in mass of fire-damaged concrete was also assessed. The test results show that the effect of temperature on mass loss of concrete with a high volume of GGBS was less than 10% for temperatures below 700°C. After being exposed to elevated temperatures, the relative compressive strength of high-volume GGBS concrete decreased more significantly than that of ordinary Portland cement concrete. The splitting tensile strength reduced significantly with increasing heating temperature. After being exposed to 300°C, the relative splitting tensile strengths of water-cooled concretes with 0%, 50%, 60% and 70% GGBS were 41·3%, 46·1%, 36·0% and 31·8% respectively. The modulus of elasticity of concrete was significantly reduced for heating temperatures up to 300°C, and the reduction was more obvious for concrete containing higher volumes of GGBS. The effect of temperature on the splitting tensile strength and the modulus of elasticity of water-cooled concrete with high-volume GGBS was more pronounced than the effect on compressive strength.