为改善高钙粉煤灰在混凝土中的体积安定性和水化活性,本文对高钙粉煤灰进行了 CO2矿化改性,研究了不同CO2矿化反应时长下高钙粉煤灰的固碳量和游离氧化钙含量,及CO2矿化改性高钙粉煤灰对水泥砂浆水化热、力学性能和孔隙结构的影响.结果表明,经12 h CO2矿化改性处理,高钙粉煤灰固碳量可超过10％(质量分数),高钙粉煤灰中的游离氧化钙含量明显降低.随着矿化反应时间的延长,掺高钙粉煤灰的水泥浆体水化诱导期缩短,早期水化放热量明显降低.CO2矿化改性处理还能减轻高钙粉煤灰对水泥砂浆强度的负面影响,改善水泥砂浆孔隙结构,降低孔隙率和大孔含量,促进水泥的早期水化和水化硅酸钙的成核结晶.
Effect of CO2-Mineralized High-Calcium Fly Ash on Mechanical Properties and Micro-Structure of Cement Mortar
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.
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