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混凝土的抗渗性,随水灰比的减小而提高;也随龄期的延长而提高,特别是水灰比较大的;掺加粉煤灰可显著提高水灰比较大的混凝土的后期抗渗性,并超过不掺粉煤灰的混凝土。混凝土工程一般在施工后相当长时间才承受水压,混凝土的抗渗性以龄期90d计是合理的。这时只要适当限定最大水灰比,其抗渗性就能满足工程要求,若掺加粉煤灰,抗渗性则更有保证。因此就可以取消混凝土的抗渗等级要求,从而可取消费工费时的混凝土渗透试验。
The impermeability of concrete increases with the decrease of water-cement ratio, but also increases with the age, especially when the water-cement ratio is relatively large. Addition of fly ash can significantly improve the post-resistance of concrete with large water-cement ratio Permeability, and more than do not fly ash concrete. Concrete projects generally take a long time after construction to withstand water pressure, impermeability of concrete to age 90d is reasonable. At this time, as long as the appropriate maximum water-cement ratio, its impermeability can meet the engineering requirements, if the addition of fly ash, impermeability is more assured. Therefore, the impermeability grade of concrete can be canceled, so as to cancel the concrete infiltration test when the working fee is paid.