关于抗冻混凝土的含气量及气泡间距临界值的探讨

Discussion on critical air content and air-void spacing for frost resistance of concrete

通过研究对水灰比、含气量对混凝土气泡结构和抗冻性的影响,FHWA质疑了ACI关于保证混凝土抗冻耐久性的含气量与气泡间距的临界值。研究结果表明,在水灰比为0.4～0.5、含气量为2.5%～4.5%范围内,含气量为3.5%和4.5%的混凝土的抗冻性能相似,耐久性系数都在80%以上。水灰比对混凝土抗冻性的影响很小,没有发现水灰比与引气混凝土抗冻性之间存在明显的联系。对混凝土抗冻耐久性具有决定性的影响是气泡间距系数,随着气泡间距的减小,混凝土的抗冻性能在提高。

The influence of water-cement（W/C） ratio and air content on the freeze-thaw resistance and microstructure was investigated,FHWA thought the critical value of freeze-thaw resistance durability was too rigorous that is constituted by ACI.The experiment was designed for concretes with fresh air contents ranging from 2.5 to 4.5 percent and W/C ratio ranging from 0.4 to 0.5,it can be indicated that the mixes with fresh air content in the levels of 3.5 percent and 4.5 percent present similar freeze-thaw resistance.They last at least 300 cycles and their durability factors are higher than 80 percent.The W/C ratio（within the range tested） does not appear to play a significant role on the freeze-thaw resistance.No trend was observed in terms of the effect of W/C ratio on freeze-thaw resistance for the mixes investigated.Nevertheless,this difference in performance seems to be much more related to the air void system than to the air content and W/C ratio,where the mix presents lower spacing factor,the better freeze-thaw resistance.