南疆盐渍土地区混凝土抗冻性能研究

Anti-frost Property of Concrete Structure in South Xinjiang Autonomous Region

通过实地调研发现,新疆南疆盐渍土地区许多混凝土建(构)筑物均不同程度地存在由盐蚀-冻融引起的混凝土表面剥蚀、开裂和疏松、粗骨料大面积裸露、盐结晶析出等病害。引起该地区混凝土产生盐蚀-冻融病害的主要原因有3个方面:(1)混凝土表层和内部的孔隙水冻结产生的拉应力;(2)渗入混凝土内部的盐类结晶产生的拉应力;(3)硫酸盐与水泥水化产物发生化学反应产生的拉应力。这些因素综合作用造成混凝土由表及里逐渐损伤、破坏和解体。通过调整混凝土水胶比、优化含气量和搅拌时间、优选骨料、使用抗硫酸盐水泥、增厚混凝土表面沥青胶泥防腐涂层厚度等工程措施,可有效提升南疆盐渍土地区混凝土结构抵抗盐蚀和冻融破坏的能力。

Field investigation reveals surface erosion, cracks and loosening, exposure of coarse aggregate in large area, as well as separation of salt crystal from concrete caused by salt corrosion and freezing-thawing damage in many concrete structures in south Xinjiang autonomous region. Three main reasons, which give rise to the salt corro-sion and the freezing-thawing damage in this region, are concluded ： 1） tensile stress generated by the freeze of pore water in concrete; 2） tensile stress produced by salt crystallization permeated in concrete; 3） tensile stress genera-ted by the chemical reaction of sulfate and hydration products of the cement. The synthetic actions of these factors give rise to the concrete damage, break and destroy from the outside to the inside. By adjusting water-bonder ratio, optimizing air content value and stir time of concrete as well as aggregates gradation, using anti-sulfate cement, and increasing the thickness of anti-corrosion coating of asphalt grout on the concrete surface, the capacity of concrete structure in resisting salt corrosion and frost damage can be improved.