掺矿渣粉水泥基材料抗干湿循环—硫酸盐侵蚀性能试验研究

Experimental study on the resistance performance of cement-based materials with slag powder to dry-wet cycling and sulfate erosion

为研究掺矿渣粉水泥基材料的抗干湿循环-硫酸盐侵蚀性能及作用机理,设计了3种矿渣粉掺量的水泥胶砂试件进行干湿循环-硫酸盐侵蚀试验,测定试件在不同侵蚀龄期下的抗蚀系数,观察其外观形态变化,并运用扫描电子显微镜观测其微观形貌。结果表明,干湿循环-硫酸盐侵蚀下,水泥基材料将受到钙矾石、石膏和十水硫酸盐晶体的叠加膨胀损伤,侵蚀破坏表现为试件抗蚀系数减小和出现剥落、砂集料外漏现象;因为矿渣粉的填充作用与火山灰效应大幅减缓了硫酸盐物理和化学侵蚀进程,所以掺矿渣粉能显著提高水泥基材料的抗干湿循环-硫酸盐侵蚀性能,其效果随着矿渣粉掺量的增加和水胶比的减小而增强。干旱区(新疆)在盐碱地中服役的混凝土结构,其水胶比宜小于0.40,矿渣粉掺量宜大于30%。将S75级矿渣粉应用于水工混凝土具有较好的实用性和经济性。

To study the resistance performance and mechanism of cement-based materials with slag powder against dry-wet cycling and sulfate attack,an experiment is designed using cement mortar specimens with three different slag powder contents.These specimens undergoes dry-wet cycling and sulfate erosion tests.The erosion resistance coefficient of the specimens at different erosion ages is measured,their surface changes are observed,and their microstructure is examined using a scanning electron microscope.The results indicate that under dry-wet cycling and sulfate attack,the cementitious materials suffer compounded expansive damage from ettringite,gypsum,and sodium sulfate decahydrate crystals.The erosion damage is characterized by a reduction in the erosion resistance coefficient and the appearance of spalling and sand aggregate leakage.Due to the filling effect and pozzolanic reaction of slag powder,the physical and chemical erosion processes of sulfates are significantly slowed down.Thus,the incorporation of slag powder can remarkably enhance the resistance of cement-based materials to dry-wet cycling and sulfate attack.This effect strengthens with increasing slag powder content and decreasing water-to-cement ratio.In arid areas like Xinjiang,servicing concrete structures in saline-alkali soils should have a water-to-cement ratio less than 0.40 and a slag powder content greater than 30%.Utilizing S75 grade slag powder in hydraulic concrete has shown good practicality and cost-effectiveness.