Research On Performance Of Resistance To Chloride Ion Penetration Time-varying Regularity In Anti-chloride High Performance Concrete

Anti-Chloride High Performance Concrete (HPC) is one of the HPC with low water-cementratio and high-quality mineral admixture. Because of its excellent resistance to chloride ionpenetration, Anti-Chloride HPC is widely used to enhance the durability of concrete structurein chloride environment. With the rapid economic development of coastal cities in China,Anti-Chloride HPC has broad prospect and has essential application value. However, theinvestigation showed that there still remained some unsloved problems in terms of materialproperties. For example, the thermo-physical properties of Anti-Chloride HPC wasunderestimated and relevant studies were limited, which resulted in the uncertainty of theincreased cracking risk. Moreover, since different specifications used different evaluationsystems of concrete resistance to chloride ion penetration performance, different conclusionsmay occurred when assessing the same concrete specimen. Plus, there was rather largedifference lies in the values of empirical coefficient of age, which was used in the chloride iondiffusion model of concrete structure’s entire life cycle. Furthermore, a suitable method tocalculate the value of empirical coefficient of age is missing in China.To solve these problems, a comprehensive study was conducted. Considerable experimentalwork was done and the thermo-physical properties of Anti-Chloride HPC were measured, inthe meantime, concrete resistance to chloride ion penetration was studied by electricitycomprehensive method with specimens of different ages within1year age and long-term trialabout the concrete resistance to chloride ion penetration time-varying regularity wascompared using natural diffusion method. In this paper, the following conclusions can bedrawn:（1）The incorporation of a large number of mineral admixtures can effectively reduce theadiabatic temperature rise of concrete. The calculation method of common concrete can beused to calculate Anti-Chloride HPC. The content, type and ratio of mineral admixture haslittle impact on concrete’s thermal conductivity, thermal diffusivity and specific heat capacity.（2）Electric accelerated test with56-day age test results is more accurate when evaluatingconcrete resistance to chloride ion permeability. As there is certain relationship between theelectricity value and chloride diffusion coefficient, two indicators, that is concrete electricityvalue and chloride ion diffusion coefficient, are available to classify concrete resistance tochloride ion penetration performance into certain categories.（3）Concrete resistance to chloride ion penetration can significantly improved as the age gose on, the exponential decay law of chloride ion diffusion coefficient is verified. Theempirical coefficient of age is affected by concrete water-cement ratio, mineral admixturescontent and other factors. Studies have shown that the equation in this article can be used tocalculate concrete empirical coefficient of age in underwater environment. Extend the curingperiod can effectively reduce the initial chloride ion diffusion coefficient of concrete while theconcrete chloride ion diffusion time decay law has almost no effect.（4）The concrete time decay law of chloride ion diffusion coefficient extracted by the testresults with the first2-year age using electric acceleration method is basically consistent withthe test results of natural diffusion method.This can effectively reflect the true law. Toincrease the accuracy of life prediction of concrete structures, this paper suggests using an ageof1year or even longer as the starting point to measure chloride ion diffusion coefficient inactual concrete structures.