荷载-干湿交替-硫酸盐耦合作用下混凝土损伤过程

研究了弯曲荷载-干湿交替-硫酸盐三因素耦合作用下的混凝土损伤劣化过程,采用环境扫描电镜(ESEM)观察了耦合作用下的混凝土微观结构演变过程.结果表明,与单一硫酸盐侵蚀相比,弯曲荷载和干湿循环都加剧了混凝土在硫酸盐溶液中的损伤程度,但干湿循环的加速损伤作用更加明显.三因素耦合作用时,当荷载率低于40％时,干湿循环是加速混凝土损伤劣化的主要因素；而当荷载率达到60％时,荷载引起的力学损伤是导致混凝土劣化的主要因素.试验还表明,在荷载-干湿交替耦合作用下,混凝土强度等级越高其抗硫酸盐侵蚀能力越强,硫酸盐浓度越大混凝土损伤越明显,粉煤灰和矿粉等矿物掺合料可显著提高混凝土抗硫酸盐侵蚀能力.

Damage process of concrete exposed to sulfate attack under drying-wetting cycles and loading

The damage process of concrete exposed to sulfate attack under flexural loading and drying-wetting cycles was systematically investigated.Environmental scanning electron microscopy(ESEM) was used to investigate the microstructure of interior concrete.The results indicate that compared with the single damage process of sulfate attack,flexural loading and wetting-drying cycles both accelerate the damage process of concrete under external sulfate attack,and the effect of the latter one is even more obvious.While coupled with the above three factors,the wetting-drying cycles and loading play the major role in the process of concrete degradation when the flexural load ratio is less than 40 % and up to 60%,respectively.In addition,under the coupling effect of loading and wetting-drying cycles,strength grade and sulfate concentration can significantly affect the damage degree of concrete,and mineral admixtures can obviously improve the ability of sulfate resistance of concrete.