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通过低气压试验箱模拟高原不同海拔地区气压环境,研究了低气压对引气混凝土含气量及气孔结构的影响。试验结果表明:环境气压的降低将显著削弱引气剂的引气能力,当搅拌气压降低至50kPa时,混凝土含气量降低约20%~49%;混凝土含气量随环境气压降低呈线性减少,初始含气量越高,随环境气压降低含气量减少速率越大;混凝土塌落度越大,其抵抗因环境气压降低造成含气量降低的能力越强;低气压下搅拌后硬化的混凝土气孔结构参数整体要劣于常压下搅拌的硬化混凝土,具体表现为气泡间距系数偏大,单位体积气泡数量较少,气泡比表面积以及气泡平均直径增大的特点,但总体上看,当混凝土含气量达到一定值后,低气压下硬化混凝土的气泡间距系数可达到在200~300μm之间。
Through the low-pressure test chamber to simulate the atmospheric environment at different altitudes in the plateau, the effect of low pressure on the gas content and the pore structure of the air-entraining concrete was studied. The experimental results show that the decrease of ambient pressure will significantly weaken the air entraining ability of air entraining agent. When the agitation pressure is reduced to 50kPa, the content of air in concrete decreases about 20% -49%. The content of air in concrete decreases linearly with the decrease of ambient pressure, The higher the gas content, the lower the rate of gas reduction with decreasing atmospheric pressure. The greater the slump of concrete is, the stronger its resistance is to reduce the gas content due to the decrease of ambient pressure. The overall stomatal parameters of concrete hardened under low pressure Which is inferior to that of the hardened concrete under normal pressure, which is characterized by the large coefficient of bubble spacing, the small number of bubbles per unit volume, the specific surface area of air bubbles and the average diameter of air bubbles. However, on the whole, when the air content of concrete reaches a certain level After the value, the air bubble spacing coefficient of hardened concrete under low pressure can reach between 200 ~ 300μm.