大掺量矿物掺合料复合胶凝材料性能研究

为降低大体积混凝土的水化热和收缩开裂风险,同时保证力学性能等服役性能,文章采用3种不同细度矿渣粉,通过与质量分数均为30%的硅酸盐水泥和粉煤灰进行复掺,制备大掺量矿物掺合料复合胶凝材料,并对其浆体的水化放热、化学收缩、孔径分布和砂浆试件的力学性能、抗开裂性能进行研究。结果表明:同时掺加3种不同细度矿渣的复合胶凝材料,由于矿物掺合料的填充作用,使其孔隙尺寸减小,密实度增加,保证了较好力学性能;同时通过优化级配,使得体系水化放热量和最大放热速率大幅度降低,化学收缩量减小,实现温和水化的作用;复合胶凝材料砂浆初始开裂时间推迟20.8%,裂缝宽度减少50%,大大降低大体积混凝土的收缩开裂风险,提升了抗开裂性能。

To reduce the risk of hydration heat and shrinkage cracking of large-volume concrete while ensuring the service performance such as mechanical properties, three types of slag powders with varying fineness were used, compounded with Portland cement and fly ash both at a mass fraction of 30%, to prepare composite cementitious materials with high-volume supplementary cementitious materials. The hydration heat release, chemical shrinkage, pore size distribution of composite cementitious material slurry and the mechanical properties and cracking resistance of mortar specimens were studied. The results show that the composite cementitious materials incorporating three types of slag powders with varying fineness demonstrate reduced pore size and increased compactness due to the filling effect of the mineral admixture, which ensures better mechanical properties. At the same time, by optimizing the gradation, the hydration heat release and maximum heat release rate of the system are greatly reduced, the amount of chemical shrinkage is reduced, and the effect of mild hydration is realized. The initial cracking time of the mortar of composite cementitious material is delayed by 20.8%, and the crack width is reduced by 50%, which greatly reduces the risk of shrinkage cracking of large-volume concrete and improves its cracking resistance.