Research on Early Hydration of Cement with Thermal Activated Coal Gangue

摘要

On the basis of the Ca (OH)_2 content in paste, the early hydration rate of cement with thermal activated coal gangue was studied. The paste composition and microstructure were analyzed by thermogravimetry-differential thermal analysis (TG-DTA), XRD, scanning electronic microscopy (SEM) and pore structure analysis. Results demonstrated that the thermal activation of coal gangue accelerated the early hydration of cement clinker obviously, and improved the activation of coal gangue itself. At the early stage of hydration, the amount of Ca (OH)_2 in cement with thermal activated coal gangue is higher than that of pure cement. The amount of Ca(OH)_2 in the cement paste was depended on the competition between precipitation of clinker and absorption of thermal activated coal gangue which also resulted in the difference of the change of Ca (OH)_2 amount and its relationship with the hydrating acceleration between pure cement and cement with thermal activated coal gangue. Results also showed that the cement with the coal gangue burnt at 700℃ has the highest hydration rate, higher mechanical strength, more gel pores and the lowest total porosity of the seven samples. The dominant hydrating product phases of the cement are C-S-H gel, Ca (OH)_2 and ettringite.