【正文】
n can also be related to poor mix design and construction process such as paction and curing . These types of deterioration can only be prevented by actions taken at the time of construction 。 there are no effective preventative actions that can be taken after construction. For example where the environment is known to contain significant quantities of sulphide it is sensible to consider the use of sulphate resisting Portland cement . In regions experiencing large numbers of freezethaw cycles frost damage to concrete can be prevented by adding air entraining agent to the concrete mix . Frost damage is worse in concrete that is saturated with salty water so techniques such as waterproofing membranes and silane treatments may be helpful . Alkalisilica reaction between aggregates and the alkali in cement can be prevented by avoiding the most reactive types of aggregate and by keeping the alkali content of the cement below the designated limit . To set up damaging stresses in concrete the ASR requires water so procedures to reduce the water content such as waterproofing membranes and silane treatments may help . If these forms of concrete deterioration take place the only viable repair method is concrete replacement which may be extensive especially for ASR where entire sections can be affected . Sulphate and freezethaw damage normally occur only in the cover 2 zone of the concrete . It is important to note that deterioration of the concrete will increase the risk of corrosion to the reinforcement because steel depassivators , like chlorides and carbon dioxide , will be able to move more easily through the concrete to the reinforcement . Deterioratio