Experimental study on residual properties of thermally damaged steel fiber-reinforced concrete containing copper slag as fine aggregate

This study intends to investigate the effect of copper slag (CS) on the hardened properties of thermally damaged steel fiber-reinforced concrete. Two water-to-cement ratios of 0.5 and 0.55 are considered for the concrete mixture. Different volume fractions of 0, 0.5, 1.0, and 1.5 are considered for steel fiber. Thermal cycles of 28 and 56 are considered in the experimental program. Ultrasonic pulse velocity technique is used to monitor internal damages due to the thermal cycles. Overall results show that concrete mixtures containing copper slag have considerable thermal resistance compared to the reference mixtures. However, results recommend the optimum content of 1% for steel fiber, while further addition causes lower thermal resistance of CS-modified concrete. Also, regression equations are proposed for residual compressive and tensile strengths of thermally damaged CS-modified concrete. Results show good agreement between the experimental database and the proposed regression equations.