In this paper, the heat-activated conditions of Neimenggu high aluminum coal gangue were studied, and then, the activated coal gangue as a supplementary cementitious material was used in concrete to investigate the application effect. The result shows that the optimal calcining temperature of high aluminum coal gangue is 800°C, the setting time of concrete was postponed, the slump was reduced and the resistance of concrete to chloride ion penetration was improved for the use of activated coal gangue. The compressive strength of concrete was enhanced when cement was replaced by 20%～30% activated coal gangue powder. Pozzolanic effect of activated coal gangue in the early age (7d) is higher and it can promote the hydration of cement with each other.
The effects of amounts of the kiln dust-activated coal gangue on the setting time and compressive strength of high-content slag cement were investigated. The performance of sulphate resistance of cement with 30 wt.% kiln dust-activated coal gangue was evaluated. The results reveal that the setting time of high-content slag cement is prolonged. Appropriate kiln dust-activated coal gangue amounts can increase the compressive strength, while too much activated coal gangue (>30 wt.%) leads to the decrease in compressive strength. Cement with 10 wt.% kiln dust-activated coal gangue exhibits a good compressive strength. The performance of sulphate resistance of Portland cement with 30 wt.% kiln dust-activated coal gangue is distinctly enhanced, while that of high-content slag cement is improved to some extent.
Through determining Ca(OH)2 content and chemically combined water content, hydration degree of cement with added-calcium thermal activated coal gangue may be analyzed. Variation of mineral composition during hydration process of system was analyzed by X-ray diffraction(XRD) method. Simultaneously, specific strength index was applied to study pozzolanic effect of activated coal gangue. The results can show high contribution of added-calcium coal gangue calcined at 1050°C for pozzolanic properties and high hydration reaction degree in this kind of activared coal gangue cement system, with fewer Ca(OH)2 content, more chemically combined water content and obviously reduced hydration product Ca(OH)2 at each age.
Microwave activated coal gangue is a complex process, which is bound up with irradiation time, fineness, composition and other factors.Coal gangue is not easily absorbed substances,so it could be get microwave energy for activation from strong wave absorbing materials. In this paper,as influence of the activation process of coal gangue by microwave irradiation time, establish the computer simulation model by ANSYS.As a reference to modify the activation process,improve and perfect the model of microwave activated coal gangue.
In this paper, the Neimenggu high alumina coal gangue was calcined at 400°C~1000°C, its micro-structure in different calcining temperature was studied using XRD and IR, and then the preferred activated condition and the PAI were investigated by testing the strength of cement mortars with activated coal gangue. The result shows that: the optimal calcining temperature of the gangue is 800°C, at this temperature the high activated SiO2 and AI2O3 can be decomposed from the gangue. The activity of the original gangue is very high, the PAI of the cement mortars with 800°C activated coal gangue can achieve to 126%, and thus can be used as high activity cement admixture. The PAI of the high alumina gangue is higher than that of coal gangue from other parts of China.
Three kinds of complex chemical activators were prepared and then introduced into calcined coal gangue cement. Physical and mechanical properties such as mortar fluidity and mortar strength and shrinkage were tested. The results can show that: excitation effects of multiple complex chemical activators may obvious, where with 8% of J1, 50% of cement replaced with activated coal gangue, compressive strength of the system at ages of 28 days can reach 40.7MPa. Compared with coal gangue cement system without exciting agent, in calcined coal gangue cement system with complex activators early shrinkage increased obviously and later shrinkage may be equivalent to that of pure cement.