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现浇混凝土受气候因素影响较大,温度的变化除了对水泥的水化反应速度有影响外,还对混凝土有一定的破坏作用。正如实验结果表明,现浇混凝土在-5℃的温度下冻一天再标养28天,其强度损失了原设计强度的45%。而地处冻融循环次数频繁的北方,受正负温交替影响,在200号混凝土预养强度达到6～50公斤/厘米~2时,冻融15次,可使其强度下降23%～5%。因此,在北方如何保证常年连续施工,如何减少能源消耗,确保混凝土的质量,缩短养护期,这是建筑工程技术人员必须解决的课题。混凝土冬季施工的任务就在于使混凝土在受冻前能达到的强度应大于它的临界强度。普通混凝土允许受冻强度(临界强度),在现行规范中定为达到设计强度的40%或达
The cast-in-place concrete is greatly affected by climatic factors. In addition to the effect of temperature on the hydration reaction rate of the cement, it also has a destructive effect on the concrete. As the experimental results show, the cast-in-place concrete is frozen for another 28 days at a temperature of -5°C, and its strength is lost by 45% of the original design strength. In the northern part where the frequency of freezing and thawing cycles is frequent, alternating positive and negative temperatures affect the strength of No. 200 concrete at 6 to 50 kg/cm~2, and the freeze-thaw cycle can reduce the strength by 23%~5. %. Therefore, how to ensure continuous construction throughout the year in the north, how to reduce energy consumption, ensure the quality of concrete, and shorten the maintenance period are problems that must be solved by construction engineers. The task of concrete construction in winter is to make the concrete reach its strength before freezing is greater than its critical strength. Ordinary concrete allows frozen strength (critical strength), in the current specification is set to reach 40% of the design strength or up to