盐冻条件下水泥砂浆受风沙冲蚀磨损性能及损伤机制

通过气流挟沙喷射法对水泥砂浆进行了复合盐-冻融循环后气-固两相流冲蚀磨损试验研究。基于SEM、激光共聚焦显微镜（LSCM）和XRD，观测了水泥砂浆试件冲蚀磨损后表面微观形貌，分析了盐冻前后其表面化学成分，探究其冲蚀损伤机制。结果表明：相同冲蚀试验条件下，水泥砂浆试件冲蚀率随冲蚀角度的增加而增大，在高冲蚀角下的增长趋势较为缓慢；冲蚀率随复合盐-冻融循环次数的增加出现先减小后增大的趋势，在冻融10次时冲蚀率最小；同等条件下，8%浓度下的冲蚀率均大于10%浓度下的冲蚀率。冲蚀损伤过程中动能法向分量起决定性作用，明显特征表现为冲蚀坑和微破坏区的出现。复合盐-冻融循环对冲蚀磨损性能的影响主要体现在两个方面：物理方面，表现为降温过程中溶液过饱和晶体析出以及冰胀压和渗透压对内部孔隙的作用；化学方面，溶液中的阴离子与水泥砂浆发生化学反应，生成钙矾石和石膏晶体填充在水泥砂浆内部，提高了其致密性，但后期晶体压力的增大会促进裂缝的产生，对水泥砂浆抗冲蚀磨损能力产生不利影响。

Erosion-wear performance and mechanism of cement mortar subjected to freeze-thaw cycles in salts solution

Erosion-wear performance in gas-solid of cement mortar subjected to freeze-thaw cycles in composite salts solution was studied by using sediment-air injection method. Based on the SEM, the laser scanning confocal microscopy (LSCM) and XRD, surface morphologies of specimen after erosion and the chemical composition of specimen surface before and after freeze-thaw in salts solution were measured to explore the erosion damage mechanism. Results show that in the same erosion conditions, erosion rate increases as the impact angle increase, and the growth tendency in the high impact angle is relatively slower; The erosion rate firstly decreases and then increases with the increasing freeze-thaw cycles in composite salts solution, and the erosion rate reaches minimum at freeze-thaw of 10 times; Under the same condition, the erosion rate in 8% concentration is a little higher than that in 10% concentration. In the erosion damage process, normal components of kinetic energy play a decisive role, which is characterized by the emerging of erosion pits and micro-damage zones. The effect of freeze-thaw in composite salts solution on erosion-wear performance is mainly reflected in two aspects as follows. Physical aspects:the effect of supersaturated solution crystallization in the cooling process, ice expansion pressure and osmotic pressure on internal pores; Chemical aspects:ettringite and gypsum crystal generated through the chemical reaction between anion and cement-based materials filling in inside of cement mortar, improving its compactness. However, the increasing pressure can promote crack formation in the later stage, which has a negative effect on the erosion-wear resistance of cement mortar.