半浸泡下纳米SiO2对水泥砂浆抗硫酸盐侵蚀能力的影响

Effect of Nano-SiO2 on Sulfate Resistance of Cement Mortar under Partial Immersion

研究了半浸泡条件下不同粒径(10,50 nm)与掺量(0%,1%,3%和5%)的纳米SiO2(NS)对水泥砂浆抗硫酸盐侵蚀能力的影响.侵蚀前,对NS复合砂浆的孔结构进行了分析,并测试了砂浆受侵蚀后的质量损失率、线性膨胀率以及抗折和抗压强度损失率,并利用扫描电镜(SEM)与X射线衍射仪(XRD)分析了砂浆浸泡区和干燥区的微观形貌与物相组成.结果表明:NS细化了砂浆内部孔隙并降低了孔隙连通性,增强了水泥砂浆在半浸泡下的抗硫酸盐侵蚀能力,且增强作用随着NS掺量的增加而增加,同时粒径为50 nm的NS增强效果优于粒径为10nm的NS增强效果;砂浆浸泡区与干燥区的内部均生成了钙矾石和石膏晶体,而干燥区内部没有无水芒硝结晶,说明干燥区破坏的主要原因是硫酸盐化学侵蚀.

The effects of different particle sizes(10,50nm)and content(0%,1%,3% and 5%)of nano-SiO2(NS)on sulfate resistance of cement mortar under partial immersion were investigated.Before sulfate attack,the pore structure of NS blended mortar was analyzed.The mass loss ratio,linear expansion ratio as well as flexural and compressive strength loss ratio of attacked mortar were measured.The microtopography and phase composition of the immersed zone and drying zone of mortar were analyzed by SEM and XRD.The results show that NS can refine the internal pores of mortar and reduce the pore connectivity,enhance the sulfate resistance of cement mortar under partial immersion,and the enhancement increases with the increase of NS.Meanwhile,NS with particle size of 50 nm has better enhancement effect than NS with particle size of 10 nm.Ettringite and gypsum crystals are formed in the immersed zone and drying zone of mortar,but there is no thenardite crystallization in the drying zone,indicating that the main reason for the damage in this zone is chemical sulfate attack.