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/SiO2ratios 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/SiO2ratio of 1.13 is relatively poor.