普通混凝土在盐湖环境中的抗卤水冻蚀性与破坏机理研究

采用快冻法测定了普通混凝土在新疆、青海、内蒙古和西藏盐湖卤水环境中的抗卤水冻蚀性,提出了混凝土在盐湖卤水的物理化学腐蚀和冻融循环双重因素作用下的冻融破坏机理,定量研究了混凝土的冻融损伤叠加效应与交互作用。结果表明,普通混凝土在不同冻融介质中的耐久性顺序是:青海盐湖卤水>新疆盐湖卤水>水>西藏盐湖卤水>内蒙古盐湖卤水;其冻融破坏特征是盐结晶压导致混凝土膨胀开裂。盐湖卤水对于混凝土冻融的损伤效应,既有降低冰点、缓解冻融的损伤正效应,也有促进盐类结晶、导致混凝土膨胀开裂的损伤负效应,两者之间的大小决定了混凝土在盐湖卤水中冻融时的损伤规律。

RESEARCH ON BITTERN-FREEZING-THAWING DURABILITY AND DESTRUCTIVE MECHANISM OF ORDINARILY CONCRETE EXPOSED TO SALT LAKES

Bittern - freezing - thawing durability of ordinarily concretes exposed to salt lakes in provinces of Xinjiang, Qinghai, Neimenggu and Xizang was determined by the accelerated freezing - thawing test. The destructive mechanism of ordinarily concretes under the combined reactions of two durability-factors, i. e. freezing - thawing cycles and physical - chemical corrosion of salt lake bittern, was proposed. The superposition and interaction effects of concrete damage caused by freezing - thawing cycles were quantitatively analyzed. According to the analysis durability of ordinary concrete soaked in various bitterns in de-scendent sequence is that from Qinghai, Xinjiang, pure water, Xizang and Neimengu. Freezing - thawing damage of concretes saturated in bitterns was characterized as cracking caused by salt crystallization swelling. Damage effects caused by bittern -freezing - thawing is comprised of both positive effects including lowering ice point and abating freezing - thawing damage, and negative effects such as accelerating salt crystallization and inducing concrete expansion cracks. Bittern - freezing - thawing damages of concrete are determined by the equilibrium of the above-mentioned two kinds of effects.