Test research on hydration process of cement-iron tailings powder composite cementitious materials

Abstract

Cement-based composite cementitious materials (CCMs) were prepared using mechanically ground iron tailings powder (ITP) to partially replace cement. The hydration heat, non-evaporable water (n-EW) content, Ca(OH)2 (CH) content, ITP reaction degree, and mortar compressive strength were tested to understand the hydration of the CCMs. The test results show that the addition of ITP postpones the emergence of the hydration exothermic peak and reduces the hydration cumulative heat release and exothermic rate. Moreover, the n-EW and CH content of the CCM paste at the specified age are lower than those of the cement paste, and the reaction degree of ITP increases with aging. However, it does not exceed 40% at 90d age. Compared with the cement mortar, the composite mortar compressive strength decreases to different degrees, and the rate of decrease declines with age. Early-age high-temperature curing is beneficial to the early hydration of the CCMs. However, it has a lesser or a negative influence on the middle and late hydration. This study shows that the supplementary cementitious effect of mechanically ground ITP changes the hydration process of cement-based cementitious materials, which in turn affects their performance. The result of each test correlates well, laying a reliable foundation for revealing the hydration mechanism of cement-ITP CCMs.