| Carbonation of concrete and high content of chlorine in concrete are the major causes of the corrosion rate of rebar to be greatly accelerated and the premature failure of reinforced concrete structure. Owing to the lack of curing, carbonation depth of low-grade concrete, which has a high content of mineral admixture, develops rapidly; what's more, sea sand or other raw materials which have excessive chlorine ion content are still used in some places, where people is on impel of various benefits or supervision isn't strict. They do harms to the durability of reinforced concrete structure, which is not only related to people's lives and property safety, but also one of the issues can not be ignored which is in response to the global energy conservation and sustainable development. It has important theoretical and engineering significance to study the change of corrosion rate under these two factors'interaction, which will contribute to reveal the key factors of corrosion in actual civil engineering, how to take effective measures to reduce the corrosion and extend the durability of reinforced concrete structures.A survey of natural condition of temperature and relative humidity, also the Chlorine ion content of concrete raw materials, in some parts of the Pearl River Delta was made firstly. Under some simulations in laboratory, the influence on corrosion of concrete can't receive normal curing, as the premature removal of the template, and the problem that chlorine content has not been strictly monitored in the use of concrete raw materials were lucubrated, The detail information of corrosion under the three kind of different simulated curing conditions similar to actual civil engineering construction curing, which are affected jointly by carbonation depth development and chlorine content, was investigated via the nondestructive method of the precise electrochemical linear polarization. The mechanism of influence was analyzed via MIP and the test of mortar's pH surrounded by rebars.The following results of rebars'rusting in C25 concrete, which had a high content of mineral admixture, were obtained.①Curing condition and chlorine ion both had effect on rusting, but the content of chlorine ion effected more obviously before the concrete cover received carbonation.②Because of the lack of wet curing, the amount of porosity and macrospore(>100nm) increased. After the concrete cover was carbonized, also the carbonation depth developed rapidly. And carbonation of concrete cover was the key reason to cause rusting under the joint effect of carbonation and chlorine content. So the rapid carbonation of concrete cover will be more serious than the common chlorine content in civil engineering construction.③Because the carbonation depth of concrete cover developed rapidly after nonstandard curing, the rusting rate of rebars was faster than that after standard curing. There should be at least a certain thick of unneutralized remainder left to keep the corrosion current density (CCD) won't exceed 1.0μA/cm2 and appear high rate of rust. For the rebar is at a common concrete cover depth of 25mm and under the assumption of chlorine content is less than or equal to 0.24%, the least unneutralized remainder should be more than or equal to 11mm under the 20±3℃,RH≥95% standard curing; the least unneutralized remainder should be more than or equal to 12mm under the 20±3℃,85±5%RH nonstandard curing; the least unneutralized remainder should be more than or equal to 18mm under the 35±3℃,75±5%RH nonstandard curing.
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