低气压环境对混凝土含气量及气泡稳定性的影响

Effect of Low-Pressure of Environment on Air Content and Bubble Stability of Concrete

通过低气压试验箱模拟高原不同海拔地区气压环境,研究了低气压环境对引气混凝土含气量及气泡稳定性的影响。结果表明：环境气压的降低能够显著削弱引气剂的引气能力,混凝土含气量随环境气压降低呈线性减少,当环境气压降低至50 k Pa时,混凝土含气量比常压环境下降低约28%～52%。低气压环境使引气混凝土气泡稳定性变差,在搅拌结束50～55 min内,低压引气混凝土含气量经时损失较大,且气泡间距系数明显增大;延长振捣时间会使低压引气混凝土损失更多气泡,从而导致含气量降低幅度以及间距系数的增大程度均大于常压引气混凝土。

The effect of low air pressure of environment on the air content and bubble stability of air-entrained concrete was investigated in a low air pressure test chamber to stimulate the plateau environment. The results indicate that the decrease of air pressure of environment has notable impact on the performance of air-entraining agents. The air content of fresh concrete decreases linearly with the drop of air pressure. The air content of fresh concrete decreased by 28%-52% at the air pressure of 50 kPa. The bubble stability of concrete mixed at a low air pressure is poor. The air content of fresh concrete mixed at a low air pressure decreases more rapidly within 50-55 min after mixing, and the spacing factor increases with the time. The concrete mixed at a low air pressure will lose more air content when vibration time increases, leading to the decrease of air content and the increase of spacing factor, which are more significant than the concrete mixed at normal pressure.