掺钢渣复合掺合料的高性能混凝土抗硫酸盐侵蚀性研究

采用干湿循环加速侵蚀试验方法,通过测定基准试件及掺钢渣复合掺合料试件在Na2SO4溶液(质量分数为5%)中干湿循环n次后的抗压强度值和质量,计算高性能混凝土(HPC)的强度耐侵蚀性系数Kf和质量损失率Kw; 采用现代测试分析方法对代表性试件进行微观分析。结果表明:当干湿循环次数达到90次、120次、150次时,生成的钙矾石晶体显著增多,膨胀破坏作用增大,随着干湿循环次数的逐渐增加,Kf逐渐减小,而Kw逐渐增大; 钢渣复合掺合料对改善HPC的微观形貌及孔隙结构、减少膨胀性水化产物具有明显作用,从而提高了HPC抗硫酸盐侵蚀性。其中将钢渣粉与粉煤灰、硅灰按体积比5:6:1的比例配制钢渣复合掺合料并取代60%水泥时,HPC的抗硫酸盐侵蚀性最好。
Sulfate erosion is one of the main factors that affect the durability of high performance concrete(HPC). The steel slag compound admixture was added into the HPC to improve its sulfate erosion resistance. Sodium sulfate(Na2SO4)solution(5 wt%)was used as erosion medium, and the drying-wetting cycle accelerated erosion tests(each cycle takes 24 h with wetting time of 15 h and drying time of 6 h )were finished by the HPC samples added with steel slag compound admixture and reference samples. The cycle numbers were 30 times, 60 times, 90 times, 120 times and 150 times, respectively. The compressive strength and mass of concrete samples(cube with a side length of 100 mm)were measured after each drying-wetting cycle erosion test, and then corrosion resistance coefficient of compressive strength(Kf)and mass loss rate(Kw)were also calculated. The Kf and Kw were used as the evaluation indexes of sulfate erosion resistance of the HPC. The erosion test(cycles of 90 times, 120 times and 150 times, respectively)results indicated that Kf gradually decreased, and Kw gradually increased with the increase in drying-wetting cycle numbers. However, Kf of concrete samples added with steel slag compound admixture was higher than those of the reference concrete samples, and Kw of concrete samples added with steel slag compound admixture was lower than that of the reference concrete samples. Therefore, it indicates that steel slag compound admixture is greatly conductive to improve the sulfate erosion resistance of the HPC, particularly the admixture constituents including steel slag powder, fly ash and silica fume being more significantly. Among them, the steel slag powder and fly ash and silica fume are replaced by 60% steel slag compound admixture according to the proportion of 5:6:1, and the HPC has the best sulfate resistance. Representative specimens JZ and GFG3 were used to microscopic analysis. It is observed that the steel slag compound admixture significantly affects the improvement in micro-topography, pore structure, and decrease in the swelling hydration products of concrete, which improves the sulfate erosion resistance of the HPC