混凝土冻融
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Damage to concrete from freezing and thawing arises from the expansion of pore water during freezing; 混凝土因冻融引起的破坏是由结冰后孔隙水的膨胀造成的; in a condition of restraint, if repeated a sufficient number of times, this results in the development of hydraulic pressure capable of disrupting concrete. 在某一约束条件下,如果重复足够多次,这就会导致液压的发展,从而引起混凝土破坏。Road kerbs and slabs, dams and reservoirs are very susceptible to frost action.路缘石,混凝土路面,大坝和水库都很容易受到冰冻作用。
The resistance of concrete to freezing and thawing can be improved by increasing its impermeability. 混凝土的抗冻性,可以用增强其抗渗性来提高。This can be achieved by using a mix with the lowest possible water cement ratio compatible with sufficient workability for placing and compacting into a homogeneous mass. 在和易性满足条件的前提下,以最低的水灰比来制作混凝土,放至均质体中并压实。 Durability can be further improved by using air entrainment, an air content of 3 to 6 percent of the volume of concrete normally being adequate for most applications. 耐久性可以通过使用引气剂而进一步提高,通常空气含量占混凝土体积的3%~6%即可胜任大部分应用The use of air-entrained concrete is particularly useful for roads where salts are used for deicing.。引气混凝土的使用,尤其对需用盐除冰的道路非常有用。
Chemical Attack In general, concrete has a low resistance to chemical attack. 一般而言,混凝土的抗化学侵蚀能力很低. There are several chemical agents, which react with concrete, but the most common forms of attack are those associated with leaching, carbonation, chlorides and sulphates. 有很多种化学物质会与混凝土发生反应,但最常见的形式与淋滤作用,碳化,氯化物和硫酸盐有关。 Chemical agents essentially react with certain compounds of the hardened cement paste and the resistance of concrete to chemical attack, therefore, can be affected by the type of cement used. 化学物质本质上是与某些水泥石化合物发生反应。因此,混凝土的抗化学侵蚀能力与所使用的水泥种类有关。 The resistance to chemical attack improves with increased impermeability. 抗化学侵蚀能力随抗渗性的提高而改善。