采用不同配合比的混凝土试件标准养护28 d后,用Autocalm 表面渗透性测试仪检测混凝土表面层的渗水系数,研究表层渗水性能的影响因素及其作用规律。研究发现,水灰比对混凝土的表层渗水性能有较大影响,C2混凝土的表层渗水系数是 C1的0.59倍,C3是C1的0.31倍,水灰比与表层渗水系数之间存在线性关系；粉煤灰的掺入,一方面由于填充效应会降低混凝土的表层渗水系数,另一方面由于延缓水泥浆体水化会增大表层的渗水系数,粉煤灰对表层渗透性能的影响是这两方面相互作用的结果；粉煤灰掺入比例为15%时,与普通混凝土相比,表层渗水系数减小,掺量达到30%时,表层渗水系数和普通混凝土几乎相同。
In this paper,factors that influence the surface permeability of concrete and their action mechanisms are studied.In the experiments,concrete specimens with different mix proportions are cured under standard condition for 28 days,then their surface permeability indexes were tested by Autoclam.It was found that the water-to-cement ratio influences the surface permeability significantly.The surface permeability indexes of con-cretes C2 and C3 are 5 9% and 3 1% of that of concrete C1 ,respectively.A linear relation can be drawn between the surface permeability and the water-to-cement ratio.The incorporation of fly ash may decrease the surface permeability of concrete due to its micro-filler effect on the one hand,and may increase the surface permeability at early ages due to its hydration retardation effect.The overall influence of fly ash should be attributed to the combined effect of these two mechanisms.A fly ash replacement ratio of 1 5% results in lower surface permea-bility,as compared with the reference concrete.However,when the replacement ratio was as high as 30%,the surface permeability was comparable with that of the reference concrete.
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