混凝土是一种人造石材,其强度主要是水泥和水的水化水解反应生成水泥石的结果。这种水化、水解反应需要一定的温度、湿度条件。温度愈高,反应愈快;温度愈低,反应愈慢。当温度降低到一定程度时,这种反应趋于停止。温度的变化除了对水泥的水化反应速度有影响外,还对混凝土有一定破坏作用。混凝土浇注后突然遭到冻结,或经过预养但未达到一定强度就遭到冻结,则混凝土中尚未参与水化反应的水分,由水的性质和孔隙特征所决定,其中一部分将结成冰。水结冰产生的压力使混凝土体内微弱的水泥石结构产生微裂纹,降低了强度。试验表明,经过一定时间预养再受冻的混凝土与浇注后立即受冻的混凝土相比,化冻后总的水化产物数量显著增多,强度降低较少或不降低。转入正温后,水化反应又继续进行,可以达到设计标 Concrete is a kind of man-made stone whose strength is mainly the result of hydrolytic reaction of cement and water to produce cement stone. The hydration and hydrolysis reactions require certain temperature and humidity conditions. The higher the temperature, the faster the reaction; the lower the temperature, the slower the reaction. When the temperature drops to a certain degree, this reaction tends to stop. In addition to the effect of temperature on the hydration reaction rate of the cement, the temperature change also has a destructive effect on the concrete. After the concrete is suddenly frozen after being poured, or it is pre-prepared but is frozen without reaching a certain strength, the moisture in the concrete that has not participated in the hydration reaction is determined by the nature and pore characteristics of the water, and part of it will form ice. The pressure generated by water freezing causes micro-cracking in the weak cement stone structure in the concrete, which reduces the strength. Tests have shown that, after a certain period of time pre-recovery and then frozen concrete compared with concrete immediately after being poured, the amount of total hydration products after thawing significantly increased, and the strength decreased less or not. After entering the positive temperature, the hydration reaction continues and can reach the design target