碳化对钢渣-水泥-CaO-MgO砂浆强度和微观结构的影响

Effect of Carbonation Curing on Mechanical Strength and Microstructure of Mortars Prepared with Steel Slag-Cement-MgO-CaO Blends

以钢渣粉为主要胶凝材料,掺入MgO,CaO和水泥等材料制备砂浆试件,经碳化养护后测试其抗压强度及微观结构,并研究碳化后砂浆试件的强度变化机理.结果表明:经碳化处理后,砂浆试件抗压强度显著提高,碳化1d后即提高3.9~6.8倍,且砂浆试件碳化时间越长,碳化程度越高,其抗压强度也越高;CaO和MgO的掺入有利于碳化后砂浆强度的提高,当掺入5%(质量分数)CaO和15%(质量分数)MgO时,碳化14d后砂浆试件抗压强度最高,可达71.6MPa;碳化过程中生成了大量碳化产物——方解石CaCO3(碳酸钙镁CaxMg1-xCO3)和文石CaCO3,碳化产物填充孔隙、改善了颗粒界面结构,使得砂浆试件孔隙率降低,抗压强度得以提高.

Steel slag powders were used as the main component of cementitious materials,and MgO,CaO and Portland cement were incorporated to prepare mortar specimens.The mortars were then exposed to CO2 curing to test the compressive strength and microstructure and investigate the mechanism of improving strength of carbonation curing.The results show that the compressive strengths of mortars increase significantly after the carbonation curing,by 3.9-6.8 times after only 1 dof carbonation.Prolonging the carbonation curing time facilitate the carbonation reaction,and hence increases the degree of carbonation and enhances the strength gain of mortars.The incorporation of CaO and MgO components increases the compressive strengths of mortars,and the highest compressive strength can reach 71.6 MPa after 14 dof carbonation,when 5%（by mass）CaO and 15%（by mass）MgO are incorporated.The treatment of CO2 curing decreases the total pore volume of mortar specimens due to the microstructure densification as a result of the formation of calcite CaCO3（calcium magnesium CaxMg1-xCO3）and aragonite CaCO3.