冻融与侵蚀作用下引气混凝土劣化微观机理

对经历冻融循环和海水浸泡交替作用后含气量为5.9%的引气混凝土试件进行抗压强度、质量损失、相对动弹性模量及扫描电子显微镜检测,以研究冻融循环和海水浸泡交替作用下引气混凝土的劣化机理.通过观察引气混凝土试件表面和中间处的微观结构,发现未受到冻融循环时,几乎不见裂缝和晶体,随着冻融循环次数增加,微裂缝逐渐发展,当冻融循环达到300次时,主裂缝深入发展,并有晶体产生.可见海水侵蚀和冻融循环交替作用,导致微裂缝产生并发展,同时化学反应产生了晶体.物理和化学损伤累积导致引气混凝土抗压强度降低达8.5%,但是相对动弹性模量和质量损失在冻融循环和海水浸泡交替作用前后均变化较小.

Degradation mechanism of air-entrained concrete under alternative actions of freeze-thaw cycles and seawater immersion

Experiments had been done on air-entrained concrete test cubes(air content is 5.9%) experienced alternative actions of freeze-thaw cycles in the seawater to explore the properties deterioration mechanism via testing the compressive strength, the relative dynamic elastic modulus and the mass loss. Then, observing the microstructure of the concrete by scanning electron microscope (SEM). The SEM observation shows that there was barely cracks and crystals in the normally cured concrete, but cracks emerged and gradually developed as the times of freeze-thaw cycle increased. The main cracks developed further and crystals emerged in the concrete experienced 300 cycles. The results show that the alternative actions of freeze-thaw cycles and seawater immersion give rise to the emergence and development of the cracks, chemical reactions produce some dilatability crystals. Both of the physical changes and the chemical reactions make the compressive strength decrease by 8.5%, but have no apparent influence on the relative dynamic elastic modulus and the mass loss.