寒区面板混凝土抗冻耐久性研究

Research on frost-resisting durability of concrete face slab in cold region

混凝土面板的抗冻耐久性对堆石坝的服役寿命和抗渗性能有重要影响。以典型配合比的面板混凝土为研究对象,在控制相同流动度和含气量的情况下,采用快速冻融试验方法研究了掺入膨胀剂、聚乙烯醇纤维和减缩剂对面板混凝土抗冻融破坏能力的影响,并结合气孔结构分析技术揭示了面板混凝土抗冻融耐久性受影响的机理。结果表明:通过对含气量和气泡结构的优化,可以配制出抗冻等级不低于F400的高抗冻面板混凝土;质量损失和相对弹性模量对该面板混凝土抗冻能力的表征具有高度的一致性;轻烧MgO型膨胀剂和减缩剂对引气剂效果有影响,可降低面板混凝土的抗冻能力,而聚乙烯醇纤维对引气剂效果的影响较小,制备高抗冻面板混凝土时,应优先考虑聚乙烯醇纤维,但MgO型膨胀剂和减缩剂的使用需仔细评估。

Frost-resisting durability of concrete face slab is very important for the service life and impermeability of Concrete-face Rock-filled Dam (CFRD). Taking the concrete with typical mix proportion as the object, under the condition of controlling the same mobility and gas containing content, the rapid freeze-thaw test method was used to study the effect of doping expansive agent, polyvinyl alcohol fiber and shrinkage reducing agent into concrete on frost-resisting durability. Then combined with pore structure analysis technology, the mechanism of freeze-thaw durability of concrete slabs was revealed. The results showed that the face concrete with the frost resistance grade not less than F400 can be prepared by optimizing the gas content and bubble structure. The mass loss and relative elastic modulus were highly consistent with the frost-resisting of the concrete. The effect of air-entraining agent was affected by lightly burned MgO expansion agent and shrinkage reducing agent, which can reduce the frost-resisting of face concrete. Polyvinyl alcohol fiber had little effect on the air-entraining agent effect. Polyvinyl alcohol fiber should be given priority in the preparation of high frost-resisting concrete, but the use of MgO expansive agent and shrinkage reducing agent should be carefully evaluated.