CO₂ 矿化改性高钙粉煤灰对水泥砂浆力学性能和微结构的影响

To improve the volume stability and hydration activity of high-calcium fly ash (HFA), CO₂ mineralization treatment was applied in this paper. The CO₂ uptake percentage and free CaO content of HFA undergone different CO₂ mineralization duration were experimentally determined. The influence of CO₂-mineralized HFA on hydration heat, mechanical properties and pore structure of cement mortar was investigated. The results show that after 12 h of CO₂ mineralization modification treatment, the carbon sequestration of high calcium fly ash exceeds 10% (mass fraction), and the content of free calcium oxide in high calcium fly ash is significantly reduced. As the prolongation of CO₂mineralization, the hydration induction period of cement slurry mixed with HFA is shortened, and the early hydration heat release is significantly reduced. CO₂ mineralization can also mitigate the adverse impacts of HFA on mechanical strength, as well as improving the pore structure of cement mortar by reducing porosity and volume fraction of large capillary pores. Besides, CO₂-mineralized HFA provides more nucleation sites for precipitation of C-S-H, accelerating the early hydration reaction of cement paste.