Evaluation of setting and hardening properties of accelerator and slag-silica fume-cements

Industrial solid waste is used as a supplementary cementitious material (SCM) to replace cement, promoting the recycling and improving resource and economic sustainability. In this study, an organic combination of SCMs was prepared, along with the preparation of composite cementitious materials (CCM) that can be tailored to the aluminum sulfate alkali-free liquid accelerators (ASALA). The findings revealed that a combination of 30% SCMs, including 10% slag, 15% silica fume, and 5% treated hardened cement powder (T-HCP), was blended with cement to form a CCM. Under the influence of the accelerator, the initial setting time of CCM is 1 min 20 s and the final setting time of CCM is 3 min. The compressive strength at 1 d, 3 d, and 28 d reaches 17.2 MPa, 29.9 MPa, and 51.6 MPa, respectively. CCM can utilize SiO2 from silica fume and CaCO3in T-HCP as the nucleus to facilitate the substantial generation of AFt and Ca(OH)2in the initial stage. It can be seen that the use of supplementary cementitious materials together with alkali-free liquid accelerators in shotcrete not only enables the utilization of solid waste but also greatly improves the performance of shotcrete.