Hydration characteristics of intermediate-calcium based cementitious materials from red mud and coal gangue

In order to deep understand the hydration characteristics of red mud-coal gangue based intermediate-calcium cementitious materials, XRD, IR, TG-DTA and MIP techniques were used to investigate the hydration products and pore structure of the hardened pastes, which formed after a hydration process of the red mud- coal gangue based intermediate-calcium cementitious materials. The results show that the hydration products mainly are C-S-H gel, ettringite and calcium hydroxide. As the dominant products, C-S-H gel and ettringite are principally responsible for the strengthening of the intermediate-calcium cementitious materials. By hydration for 1 d to 90 d, the content of calcium hydroxide increases at the initial stage and later decreases. With the progress of hydration process, the polymerization between Si-OH bonds tends to be easier, resulting in an increasing of polymerization degree of the hydration products. The red mud-coal gangue based intermediate-calcium cementitious materials with CaO/SiO2 ratios of 0.95 and 1.04 possess good pore structure of the hardened pastes, while the pore structure of the hardened paste for the material with CaO/SiO2 ratio of 1.13 is relatively poor. © Copyright.