电脉冲作用下水泥基材料硫酸盐侵蚀的影响因素

Influence factors of sulfate attack on cement-based materials subjected to electrical pulse

利用电脉冲加速外部硫酸根离子向砂浆内部迁移,研究了电脉冲作用下水灰比、侵蚀溶液种类以及电脉冲周期等因素对水泥砂浆硫酸盐侵蚀的影响,并利用扫描电镜观察受硫酸盐侵蚀后砂浆的微观结构.结果表明,硫酸钠溶液浸泡侵蚀180 d后,水灰比为0.3,0.4,0.5的砂浆抗折系数分别为1.03,0.98,0.94,抗压抗蚀系数分别为1.02,0.96,0.90;电脉冲作用下30 d后,各砂浆抗折系数分别变为0.98,0.95,0.90,抗压抗蚀系数分别为0.97,0.96,0.91,试件内部生成了大量的钙矾石,表明电脉冲加速了水泥砂浆的硫酸盐侵蚀.电脉冲作用下,在侵蚀溶液为硫酸镁的试件内部,部分水化硅酸钙(CSH)凝胶已转化为无胶凝性的水化硅酸镁(MSH),导致试件强度下降幅度大于硫酸钠侵蚀.此外,与周期为20 s的电脉冲相比,在周期为10 s的电脉冲作用下,试件受硫酸盐侵蚀的破坏程度更大.

The effects of the water-cement ratio,types of attack solution and the period of pulse on sulfate attack on cement mortars subjected to electrical pulse were investigated through electrical pulse speeding up the migration of external sulfate ions into cement-based materials.The microstructures of the damaged specimens were examined by scanning electron microscope.The results show that for the mortars with the water-cement ratios of 0.3,0.4 and 0.5,after immersion in the attack solution of Na2SO4for 180 d,the flexural coefficients are 1.03,0.98 and 0.94,respectively,and the compressive strength coefficients are 1 .02,0.96 and 0.90,respectively.However,after using electrical pulse for 30 d,the flexural coefficients are changed into 0.98,0.95 and 0.90,respectively,and the compressive strength coefficients are 0.97,0.96 and 0.91,respectively.A large amount of ettringite form in the damaged specimens,indicating that electrical pulse accelerates the erosion of cement-based mortars due to sulfate attack.When MgSO4 is used as the attack solution under electrical pulse,some calcium silicate hydrate （CSH）gel converts into non-cohesive magnesium silicate hydrate （MSH）,resulting in greater strength loss of the specimens compared with that caused by sodium sulfate attack.Moreover,the deterioration degree of the specimens subjected to electrical pulse with the period of 10 s is greater than that with the period of 20 s.