Pozzolana Activities and the Effects of Thermal Activated Coal-gangue on Cement Hydration

摘要

Chemical compositions, mineral compositions and the mechanism of activation of Coal-gangue were analyzed as well as their active compositions and contents after the activation. Hydration heat and hydrate compositions of the activated coal-gangue-calcium oxide system were studied as well as the degree of hydration and interface microstructures of hydrates of the activated coal-gangue-cement system. Results proved that pozzolana activities of the coal-gangue activated by calcinations at low temperature were derived from amorphous SiO_2 and activated Al_2O_3. With stimulation of the gypsum, activated coal-gangue could take place a secondary hydrating reaction. And from the reaction of the activated coal-gangue and the Ca (OH)_2, such hydrates as ettringite, calcium silicate hydrate, calcium aluminate that were useful to enhance the strength of cement paste were produced. In the paper, the relationship between the content of Ca(OH)_2 in the coal-gangue-cement system and the curing age was confirmed. It was proved that unhydrated particles in the coal-gangue-cement system were more than those in the neat cement paste of the same age, and unhydrated particles existed even at the late stage of the hydration. It was verified that activated the coal-gangue could decrease the content of Ca (OH)_2 in hydrates, inhibit growth and gathering of the calcium oxide crystal, and could improve the structure of hardened cement paste.