Hydration characteristics of cement-free binder using Kambara reactor slag

A cement-free binder was manufactured by utilising slag generated from the Kambara reactor stirring process as an alkali activator. Kambara reactor slag (KRS) is a byproduct of the desulfurisation process of molten iron in steel factories and is composed of calcium oxide, silicon dioxide, carbon, iron oxide and so on in the form of compounds such as calcium hydroxide, calcium carbonate and belite (2CaO.SiO2). The calcium hydroxide in the KRS could serve as an alkali activator for ground granulated blast-furnace slag (GGBFS). The compressive strength of the GGBFS–KRS binder was about 30% that of ordinary Portland cement (OPC) at age 28 d, whereas the 28 d strength of a binder made from GGBFS, KRS and anhydrous gypsum (AG) was similar to that of OPC. The main hydration product of the GGBFS–KRS–AG binder was shown to be ettringite. Scanning electron microscope images revealed that the needle-shaped ettringite of the GGBFS–KRS–AG binder was much thicker than that of OPC. The thick needle-shaped ettringite for...