热活化再生水泥砂浆的二氧化碳养护

A method for carbon dioxide curing of mortar produced with thermally activated recycled cement was proposed to improve the resource utilization for waste concrete and reduce the overall carbon dioxide emission during concrete preparation. The waste cement paste containing 0% to 30% silica fume was thermally activated at 800 ℃ to obtain reactivated cementitious materials with different calcium-to-silica ratios. The mortar with low alkalinity was prepared by gradient carbon dioxide curing. The compressive strength,phase assemblage,and microstructure of mortars were analyzed. The results show that the mineral composition of the reactivated cementitious materials obtained by mixing 0% and 10% silica fume is tricalcium silicate (C₃S),β-dicalcium silicate (β-C₂S),and α′-C₂S,and a large amount of calcite and vaterite is formed after carbon dioxide curing. However,the mineral composition is mainly α′-C₂S and monocalcium silicate (CS)after adding 20% and 30% silica fume,and the carbonation products are mainly calcite and aragonite after carbon dioxide curing. The compressive strength of the mortar samples after carbon dioxide curing is higher than 45 MPa,and the compressive strength of the mortar samples produced with reactivated cementitious materials containing 20% silica fume achieves 64. 7 MPa. The pH of the mortar specimens is reduced to 9. 4,which can effectively mitigate the performance degradation of fiber reinforced polymer in highly alkaline environments.