带初始损伤混凝土受硫酸盐侵蚀劣化的机理分析

Deterioration Mechanism of Concrete with Initial Damage Exposed to Sulfate Attack

通过测量混凝土的质量变化量和相对动弹性模量,研究了带初始损伤混凝土在干湿循环作用下受硫酸盐侵蚀的劣化规律,同时利用压汞法(MIP)、扫描电镜(SEM)和电子能谱技术(EDS),探究分析了含初始损伤混凝土在硫酸盐侵蚀作用下的孔结构和腐蚀产物组分的变化.结果表明:随着初始损伤度的增加和水灰比的增大,混凝土受硫酸盐腐蚀劣化加剧;损伤度为20%的混凝土受硫酸盐侵蚀150d后的相对动弹性模量降低至12.3%,试件部分表面剥落;大掺量矿渣混凝土抗硫酸盐侵蚀能力提高;随着腐蚀时间的增加,混凝土孔隙率增大,大孔数量增多;高水灰比混凝土内部腐蚀产物主要是石膏,低水灰比混凝土内部腐蚀产物主要是钙矾石.

The deterioration mechanism of concrete with initial damage exposed to sulfate attack under drying-wetting cycles was investigated by measurement of the mass change and relative dynamic elastic modulus（Erd）of concrete.The changes of pore structure and corrosion product composition of concrete with initial damage under sulfate attack were analyzed by mercury intrusion porosimetry（MIP）,scanning electron microscope（SEM）and energy dispersion spectrum（EDS）.The results show that with the increase of the damage degree and the water-cement ratio,the concrete was deteriorated by sulfate corrosion;the Erd of the concrete with 20% damage degree reduces to 12.3%after 150 dby sulfate attack,and the surface of the specimen tends to peel off;the high content of slag concrete can enhance the resistance to sulfate attack and low content of slag is detrimental to sulfate resistance of concrete;with the increase of corrosion time,the porosity and the number of large pores of concrete increase;the corrosion products of concrete with high water-cement ratio were mainly gypsum and the corrosion products of concrete with low water-cement ratio were mainly ettringite.