不同养护制度下粉煤灰混凝土抗硫酸盐冻融循环性能

Resistance to sulfate freeze-thaw cycles of fly ash concrete under different curing regimes

为了揭示养护制度的变化在冻融硫酸盐环境下,对粉煤灰混凝土物理力学性能影响的变化规律,将浸泡不同龄期的粉煤灰混凝土抗压强度进行测试,改变了盐冻前的养护制度,并进行了不同循环后的物理性能试验;同时,对纯水和不同浓度硫酸钠溶液低温下冻结过程进行监测。试验研究发现:首先,大掺量粉煤灰混凝土浸泡于硫酸钠溶液中随着龄期延长,抗压强度增长更快,但在高浓度溶液中浸泡60~90 d后强度出现拐点;其次,在非长龄期的硫酸盐溶液中的浸泡,提高了试件后续抵抗此环境下冻融的能力,从300个循环提高至500循环左右;最后,在冻融硫酸盐交互作用下,由于降温速度和完全冻结时长随溶液浓度增大而提高和缩短,最长缩短近200 min左右,从溶液低温化学性态的角度明晰了硫酸盐环境对混凝土抵抗冻融破坏所起的积极作用。

To reveal the law of change of curing system affecting physical and mechanical properties of fly ash concrete in freeze-thaw sulfate environment, not only soaked fly ash concrete specimens that vary by age of hardening are tested on the compressive strength, but also pre-freeze curing system is altered, with testing physical performance of the fly ash concrete specimens after different cycles. In addition, a trial test is conducted on the freezing process of such specimens soaked in pure water and sodium sulfate solution given different concentration values, under low temperature. It is indicated that(1)for the high-admixture fly ash concrete soaked in the sodium sulfate solution, the compressive strength rises in direct proportion to age of hardening but starts to decline 60~90 d after the fly ash concrete is soaked in high-concentration solution;(2) specimens soaked in non-long-aged sulfate solution show better anti-freeze-thaw capabilities than they did before soaking and bearable loop count rises from 300 to 500 or so;(3) under freeze-thaw sulfate interaction, as the cooling velocity and total freeze duration increases and decreases(max. decrease: 200 min or so) respectively by concentration of solution, it is clarified that the sulfate environment plays an active part in concrete resisting freeze-thaw damage from the perspective of low-temperature chemical form of solution.