Study of Preparation and Property of Alkali- activated cementitious materials Prepared by Red Mud and Slag

Abstract Alkali- activated cementitious materials is referred to as a green building material and a kind of eco-friendly cementitious material due to the low energy requirements compared to traditional cement and associated low CO₂ emissions from using common aluminosilicate wastes. Red and Slag are two kinds of aluminosilicate waste, respectively from aluminum industry and ironmaking industry. In this paper, a new alkali- activated cementitious material is prepared by red mud and slag. Respectively the raw material ratio, different activator dosage and hydration reaction time are evaluated. The results showed that when the sintering red mud and slag blend with a mass ratio of 5:5 were activated by sodium carbonate, the optimized content of sodium carbonate was 5.5%(calculated by mass of sodium oxide). Under this condition, the compressive strength of alkali- activated cementitious materials synthesized reached 54.4 MPa at 28d. The effects of TG, XRD and SEM-EDS showed that the main hydration products were amorphous substances including hydrated calcium silicate (C-S-H) and hydrated calcium alumino silicate( C-S-A-H). Higher strength material had more fine microstructures and much more activated products. The compressive strength of the product reachs the standard requirements of Portland cement P.O42.5.