寒区盐渍土环境下混凝土的破坏机理研究

RESEARCH ON THE DAMAGE MECHANISM OF CONCRETE BRIDGE DUE TO SALINIZED SOIL UNDER COLD ENVIRONMENT

针对吉林西部盐渍土地区混凝土在冻融、干湿和盐浸多重作用下性能衰减的问题,利用快速冻融机,进行冻融-盐浸-干湿、冻融-盐浸、冻融-干湿不同条件下的对比试验,以混凝土的动弹性模量和质量损失为评价指标,结合微观组织和XRD分析,研究了混凝土的劣化机理。结果表明:冻融-盐浸-干湿共同作用下,混凝土的性能衰减最快;不同试验条件下,混凝土相对动弹性模量与循环次数之间满足三次函数关系;混凝土的破坏是水结冰膨胀、盐结晶膨胀、渗透压增大、盐化学侵蚀等多因素相互渗透的结果,其中前两项起主要作用。

In the western region of Jilin province, the concrete structures have been suffering thecombined action of freeze-thaw, slat corrosion and dry-wet cycles, leading to deterioration of concreteperformance. The fast freezing -thawing was used to conduct the comparison experiment with thefreeze-thaw ＋ slat corrosion ＋ dry-wet cycles, freeze-thaw ＋ slat corrosion and freeze-thaw ＋ dry-wetcycles. The experiment took the loss rate of dynamic elastic modulus and quality as the evaluation in-dex, combined with microstructure and XRD analysis so as to study the degeneration mechanism ofconcrete. The results show that, the reduction of concrete performance is fastest under the condition offreeze-thaw ＋ slat corrosion ＋ dry-wet cycles. The three function relation between relative dynamicmodulus of concrete and cycle numbers is established under different experimental conditions. Thedamage of concrete is the result of multi-factor such as water infiltration, salt crystal expansion, os-motic pressure increase, salt chemical erosion and others; the first two items playa major role.