论提高中低强度混凝土的耐久性

Improving durability of medium and low grade concrete

提高混凝土耐久性的关键是提高混凝土的均匀密实性和抗裂性能.以“单位立方米混凝土最佳粗骨料用量”和“减水剂临界掺量”的新概念来指导混凝土的试配,以拌和水对净浆、净浆对砂子、砂浆对粗骨料的紧密堆积空隙的恰好或充分填充的思路,辅之以粉煤灰具有活性掺合料和微细填充料双重功能的新概念来指导混凝土配合比设计,可以大幅度提高混凝土特别是中、低强度混凝土的均匀密实性即抗渗性.建议:将GB50119标准中的水养龄期改为7 d,提高混凝土水中7 d、空气中35 d的限制膨胀率指标值,并且寻找出准确和可行的限制膨胀率检测方法,可以大幅度提高膨胀混凝土的抗裂性能。

The key to improve the durability of concrete is to improve the uniform compactness and crack resistance of concrete.The author believes that the new concepts of“the optimum amount of coarse aggregate for Concrete per cubic metre”and“the critical amount of water reducing agent”should be used to guide the trial mixing of concrete,and the idea of filling the voids of cement slurry with mixed water,sand with cement slurry,and coarse aggregate with mortar exactly or sufficiently,and the new concept of fly ash with dual functions of active admixture and micro-filler should be used to guide the design of concrete mix ratio.It can greatly improve the uniform compactness of concrete,especially the medium and low grade concrete,namely impermeability.In this paper,it is suggested that the water curing age in GB 50119 standard should be changed to 7 days,and the limited expansion rate index value of 7 days in water and 35 days in air should be increased,and an accurate and feasible method to detect the limited expansion rate should be found,which can greatly improve the crack resistance of expansive concrete.