农业工程学报Issue(11)：165-172,8.DOI:10.11975/j.issn.1002-6819.2015.11.024
高原低气压环境对引气混凝土含气量及气泡稳定性的影响
Effect of low atmospheric pressure of plateau environment on air content and bubble stability of air-entrained concrete
摘要
Abstract
The effect of atmospheric pressure reduction of environment on air content and bubble stability of air-entrained concrete were experimentally studied using low-pressure test chamber to stimulate the plateau environment. Three different mixing proportions and three different levels of the initial air content of concretes were prepared for study, and four different common types of air-entraining admixture, saponin, alkyl sulfonate, abietic soap and polyether, were used in the experiments. The results indicated that the change of atmospheric pressure of environment had a significant impact on the performance of air-entraining admixtures. When the mix proportions of concrete and the amount of air-entraining admixtures took a certain value respectively, the air content of fresh concrete decreased linearly with the drop of atmospheric pressure. When the atmospheric pressure was 50 kPa, the air content of fresh concrete fell by roughly 20% to 49%. The higher the air content of fresh concrete mixed in normal atmospheric pressure, the faster the air content of fresh concrete decreased with the drop of atmospheric pressure. Among the four common types of air-entraining admixture used in the experiment, the air-entraining ability of saponin was the least influenced by the drop of atmospheric pressure and the abietic soap was the most. In addition, the bubble stability of fresh concrete mixed under low atmospheric pressure was poor than the one under the normal atmospheric pressure. The air content of the fresh concrete mixed under the low atmospheric pressure decreased more rapidly within 50-55 minutes after finish of the mixing and the spacing factor increased obviously as time went on. Besides, whatever the concrete was mixed under the low or the normal atmospheric pressure, the air content of fresh concrete decreased and the spacing factor of hardened concrete increased with vibration time extended from 0 second to 90 seconds, but it was more obvious within 30 seconds. Therefore, in order to meet the design requirements of air content of air-entrained concrete for different constructions in the plateau regions, the following measures were recommended: 1) the air-entraining admixture with good air entraining ability and foam stabilization performance should be chosen for the plateau environment, 2) according to different pressure conditions and types of air-entraining admixture, the dosages of air entraining admixture should be increased so that air content of concrete could fully meet the design requirements, and 3) during the construction in the plateau regions, the vibration time should be reduced with the precondition of the impaction of concrete if possible to avoid air content loss.关键词
混凝土/气压/气体/气泡稳定性/引气能力/气泡间距系数Key words
concretes/atmospheric pressure/air/bubble stability/air-entraining ability/spacing factor分类
建筑与水利引用本文复制引用
李雪峰,付智..高原低气压环境对引气混凝土含气量及气泡稳定性的影响[J].农业工程学报,2015,(11):165-172,8.基金项目
国家自然科学基金项目（51308246）；交通运输部科技资助项目 （）
