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混凝土中水泥的水化程度依赖于环境温度。当新拌混凝土处于低温时,混凝土强度增长缓慢并可能因为结冰而导致混凝土冻害。在此环境下,必须采用特殊的措施来防止混凝土的早期冻害,并需认真选择材料、配合比、搅拌、运输、浇注、养护、成型和防护条件以确保混凝土按需求的强度发展。在日本土木工程学会(JSCE)混凝土结构的设计和施工标准规范中,规定当预报的日平均气温低于4℃时就必须按混凝土冬期施工条件进行施工。因为需要有特殊设施来保护新拌混凝土不受冻害,所以混凝土冬期施工往往费用较高,使用防冻剂来降低新拌混凝土的冰点是工艺简单、经济而又有效的方法。目前日本市场上有一些混凝土防冻剂,系采用含有氯离子或钠离子的化合物来降低混凝土中孔隙水的冰点,但氯离子和钠离子的存在可能会引起混凝土中钢筋的锈蚀和碱-集料反应。
The degree of hydration of cement in concrete depends on the ambient temperature. When the fresh concrete is at a low temperature, the concrete strength increases slowly and may cause freezing damage to the concrete due to icing. Under this circumstance, special measures must be taken to prevent early frost damage of concrete, and materials, mix ratios, mixing, transportation, pouring, curing, forming, and protective conditions must be carefully selected to ensure the strength of concrete according to demand. In the specification of the design and construction standards for concrete structures of the Japan Society of Civil Engineering (JSCE), it is stipulated that when the daily average temperature of the forecast is lower than 4°C, construction must be carried out according to the concrete winter construction conditions. Because it is necessary to have special facilities to protect fresh concrete from freezing damage, it is often costly for concrete to be constructed in winter. It is a simple, economical and effective method to use the antifreeze to reduce the freezing point of fresh concrete. At present, there are some concrete antifreeze agents on the Japanese market, which use compounds containing chloride ions or sodium ions to reduce the freezing point of pore water in concrete. However, the presence of chloride ions and sodium ions may cause corrosion of steel bars in concrete and alkali-aggregates. reaction.