Effect of ground granulated blast furnace slag on the properties of hybrid-fiber-reinforced high-strength concrete under normal and high temperatures

In this paper, the residual mechanical properties, mass loss, and cracking behavior of hybrid-fiber-reinforced high-strength concrete (HFRHSC) containing 0%, 30%, and 60% ground granulated blast furnace slag (GGBFS) in normal and high temperatures have been investigated. Chopped aramid and steel fibers at 0%, 0.5%, and 1% by volume, either individually or in different combinations, were used to reinforce the HSC. In total, 24 different mix proportions were designed. The experimental results showed that the residual compressive strength of the majority of specimens increased at 400? while this property of all of them decreased at 800?. Also, the test indicated that the use of GGBFS did not reduce flexural and compressive strength of HSC significantly, and in some mixed designs, the presence of GGBFS slightly increases the strength. Moreover, another result that can be inferred is that although the utilization of hybrid fibers in concrete increases flexural strength, it may decrease its compressive strength. In addition, the residual flexural strength of most specimens was reduced at 400?, but this property of all samples decreased at 800?. The results showed that the simultaneous presence of GGBFS and hybrid fibers can improve the flexural strength of most specimens at different temperatures.