Chloride Erosion Of Concrete Structures In Cold Area

Concrete durability is an issue in the civil engineering, and freeze-thaw cycles and chloride are common factors influencing concrete structural durability. In the cold area, in order to have a smooth traffic situation and try the best not to affect the normal human life, the deicing salt is often used to clear the snow and ice on the road. Although the deicing slat could solve the present problem we meet, the road will be still suffering from the damage of chloride. However, the damage for the road becomes more serious under the additional effect of the freeze thaw cycle. So many constructions have to re-built during the proper service period, which takes enormous economic losses and affects seriously the traffic.This paper by reference to the existing literature summarizes the damage characteristics and mechanism of the salt freezing to the concrete, makes the freeze-thaw experiments to study the concrete in four different concentrations of chloride solution, concludes the relationship between chloride ion concentration and slat concentration, freeze-thaw frequency, penetration depth, then obtains that the freeze-thaw under the different concentrations and different frequency situation has a relationship with the diffusion coefficient of chloride ions. The results showed that: with increasing the penetration depth, the concentration of chloride ion in concrete will decrease and the diffusion coefficient of chloride ions increases accordingly, but the growth trend is slow. Meantime, by studying the relationship between water-cement ratio, air content situation and the salt-frost resistance ability of concrete, and by comparing the experimental datum, it is obtained that when the water-cement ratio is controlled under 0.4 or less, then the concrete has a good salt-frost resistance performance; And the air content gas reaches about 6.2%, the concrete has a best salt-frost resistance performance at that time. However, when the air content continues to increase after 6.2%, the salt-frost resistance performance of the concrete will become weak. Therefore, it is proposed that air content is controlled around 5.5% level.