Residual properties of steel slag coarse aggregate concrete after exposure to elevated temperatures

Abstract

Steel slag, waste by-product during steelmaking process, has great potential in concrete production. Over the past few decades, extensive research studies were conducted on the mechanical behaviour and chemical property of concrete made with steel slag at ambient temperature. However, relatively little effort has been put to study the behaviour of concrete with steel slag after exposure to elevated temperatures. To fill up this research gap, an experimental study was conducted in which five concrete mixes with steel slag replacing natural coarse aggregate (crushed granite) were prepared. The effect of slag replacement ratio by volume (0%, 25%, 50%, 75% and 100%) on the heating behaviour, residual compressive strength, weight loss and surface texture of concrete under curing period of 28 and 91 days, after exposure to 25℃ (ambient temperature), 400℃, 600℃, 800℃ and 1000℃ was investigated. Besides, chemical deterioration behaviour was studied using X-ray diffraction analysis. From the test results, it is evident that with steel slag partially or totally replacing crushed granite, the heat insulation ability of concrete could be enhanced. Moreover, the residual strength of concrete with slag replacement ratio of 100% after exposure to elevated temperatures ≥600℃ would be comparable to concrete with crushed granite only. Lastly, the design model by EC2 was adopted to predict the residual strength of concrete with and without slag and results demonstrated that EC2 was conservative.