Hydration characteristics and sustainability of calcium carbide slag-activated full solid waste cementitious materials under high temperature curing

Abstract

Using calcium carbide slag (CCS) to replace ordinary portland cement (OPC) as an alkali activator for the preparation of full solid waste cementitious material is a green and low carbon method. This study investigates the influence of 80 °C high-temperature curing on ground granulated blast furnace slag - steel slag based supersulfated cement (GS-SSC) incorporating 0 to 20 wt% CCS. The hydration products and microstructure of GS-SSC were analysed using various microscopic techniques, assess the compressive strength and pH value development, exploring the hydration mechanism of CCS activated GS-SSC. The results indicated that the CCS could increase the alkalinity of GS-SSC, activate the pozzolanic activity of ground granulated blast furnace slag-steel slag (GGBS-SS). Compared with the control group, the CCS promote the generation of more AFt and C-(A)-S-H gels, fill the pores and microcracks of the samples, making the microstructures denser. CCS significantly increased the compressive strength of the samples under curing at high temperatures. When 10 % CCS was incorporated, the compressive strength reached 31.2 MPa at 3 d and further increased to 33.5 MPa at 7 d. Moreover, sustainability assessment results indicate that the material exhibits favorable environmental and performance sustainability under this dosage condition. It is remarkable that a higher CCS content (>10 %) has a negative effect on the compressive strength of the samples. These results provide a new approach to promote the resourceful efficient utilization of industrial solid waste and serve as a valuable reference for designing low carbon cementitious materials based on GGBS-SS.