Influence of thermally activated coal gangue powder on the structure of the interfacial transition zone in concrete

Coal gangue is a kind of solid waste produced in the coal mining and preparation. Abundant SiO2 and Al2O3 are contained in coal gangue, which has potential cementitious activity. Therefore, the preparation of cementitious materials from coal gangue powder has broad application prospects. The effect and mechanism of the cementitious activity of thermally activated coal gangue powder on the pore structure, microscopic morphology, and mineral composition of the interfacial transition zone in concrete were studied. The results showed that the flexural and compressive strengths of concrete prepared with cement replaced by 15 wt% thermally activated coal gangue powder at 800 degrees C were 0.39% and 5.94% lower than those of pure cement concrete and 7.47% and 20.17% higher than those of raw coal gangue powder concrete. Mainly because abundant active Al2O3 and SiO2 released by thermally activated coal gangue powder at 800 degrees C reacted with the cement hydration product calcium hydroxide, calcium silicate hydrate gel was produced, and then the pores in the interfacial transition zone were filled and transformed into smaller pores, resulting in the pore structure and microscopic morphology of the interface transition zone being optimized, and the bond between the matrix and aggregate becoming closer.

Automated summary

The application of thermally activated coal gangue powder in cement can optimize the pore structure and microscopic morphology of concrete, and improve its flexural and compressive strengths. The active Al2O3 and SiO2 in coal gangue can react with the hydration product of cement, leading to the formation of calcium silicate hydrate gel, which fills and transforms the pores in the interfacial transition zone, and strengthens the bond between the matrix and aggregate.