混凝土在压应力状态下的抗冻性试验分析

Experimental analysis on frost resistance property of concrete at compressive stress state

为了分析压应力对混凝土抗冻性的影响,采用无粘结预应力混凝土结构对C45混凝土试件施加应力比为0、0.4、0.5、0.6的轴向压力,进行标准快速冻融试验,每50次测量其动弹性模量、质量损失和抗压强度的变化.结果表明:应力比为0时,混凝土的质量损失和动弹性模量下降较压应力迅速,未达到抗冻标号F300;应力比为0.4、0.5的混凝土衰减趋势基本一致,抗冻性较无应力状态混凝土有所提高;应力比为0.6的混凝土,其抗冻性在两者之间,在一定应力比下轴向压应力可以提高混凝土的抗冻性能;对混凝土冻融寿命预测模型进行修正,修正后的模型具有一定的工程价值.

In order to analyze the influence of compressive stress on the frost resistance of concrete, the axial pressure with the stress ratio of 0, 0.4, 0. 5 and 0.6 was applied on C45 concrete with the non bonded prestressed concrete structure. The standard fast freezing-thawing test was performed, and the changes of mass loss, dynamic elastic modulus and compressive strength were measured at every 50 cycle times. The results show that when the stress ratio is 0, the mass loss and dynamic elastic modulus drop faster than the compressive stress, and the frost resistance grade F300 is not achieved. The attenuation tendency of concrete with the stress ratios of 0. 4 and 0. 5 is consistent, and the frost resistance is better than the concrete at the state without stress. The frost resistance of concrete with the stress ratio of 0. 6 is between those with the stress ratios of 0, 0. 4 and 0. 5. Under certain stress ratio, the axial compressive stress can improve the frost resistance of concrete. The prediction model for the freezing-thawing life of concrete was modified, and the modified model has certain engineering value.