干湿循环作用下硅粉轻骨料混凝土抗硫酸盐性能分析

Analysis of sulfate resistance of silica fume lightweight aggregate concrete under dry-wet cycle

为探究干湿循环条件下硅粉轻骨料混凝土的硫酸盐侵蚀机理,选取内蒙古和林格尔县浮石,以硅粉等质量取代6%的水泥,通过NMR技术,分析硅粉轻骨料混凝土在硫酸盐侵蚀和干湿循环耦合作用下的孔隙变化规律,利用扫描电镜观察混凝土微观形貌变化,借助XRD进行物相分析.研究表明:在硫酸盐侵蚀过程中,硅粉混凝土与普通混凝土的质量损失率变化规律一致,均在60次时出现拐点;经历90次循环后,硅粉组的最大孔隙减小了56.5%,普通组的最大孔隙减小了18.8%,证明硅粉的掺入可有效细化孔隙;循环初期两组混凝土的无害孔均低于10%,循环过程中有小孔隙向大孔隙发展的趋势;在SEM扫描电镜照片中可看到孔隙中生成的石膏与钙矾石AFt,可观察到90次循环后混凝土内部的细长裂缝;2组混凝土在经历90次循环后均出现较多的CaSO 4·2H 2 O衍射峰,生成物多为硫酸盐、碳酸盐结晶水合物.该研究成果可为在硫酸盐环境下水工构筑物的工程建设提供理论参考.

In order to explore the sulfate erosion mechanism of silica fume lightweight aggregate concrete under dry-wet cycle conditions,pumice stone in Inner Mongolia and Linger County was selected to replace 6%cement with silicon powder.Through using NMR technology,the pore change law of silica fume lightweight aggregate concrete under the coupling effect of sulfate erosion and dry-wet cycle was analyzed.The pore change law of concrete under the combined action of sulfate erosion and dry-wet cycles,and the change of concrete microscopic morphology was observed by scanning electron microscope technology,and the phase analysis was carried out by XRD.The studies results show that during the sulfate erosion process,the mass loss rates of silica fume group and ordinary group have the same change,and the inflection point appears after 60 cycles.After 90 cycles,the maximum pore of silica fume group is reduced by 56.5%,and the maximum pore of ordinary group is reduced by 18.8%,which proves that the incorporation of silica fume can effectively refine the size.The harmless pores of the two groups of concrete at the beginning of the cycle are less than 10%,and there is a ten-dency of small pores to develop into large pores during the cycle.The gypsum and AFt generated in the pores can be seen in the SEM scanning electron microscope photos,and the slender cracks inside the concrete after 90 cycles can be observed.After 90 cycles,two groups of concretes have more CaSO 4·2H 2O diffraction peaks,and the products are mostly sulfate and carbonate crystal hydrates.The research results can provide a theoretical reference for the engineering construction of hydraulic structures in a sulfate environment.