Experimental Research On The Penetration Resistance Of Chloride Ions Of Recycled Aggregate Concrete

In recent years, urban construction wasted recycling had been received widely attention, many countries have been making use of the demolished concrete wasted, which can effective conserve natural quality aggregate and rational use of natural resources, it is important for protection of the ecological environment.Because of defects that pores, interface, water absoration and so on. Leading to problems of durability of recycled concrete become the main influencing factors for applied in engineering structure. In order to promote recycled concrete applied in practical engineering structure, the problem that resistance to chloride ion permeability which become to urgently study and resolve.The major contents of this paper are summarized as follows:l.Base on ASTM1202 method for electric flux test of recycled concrete, study resistance to chloride permeability of recycled concrete under the influence of recycled coarse aggregate replace rate, mineral admixture types, different mix methods and curing age. also analysis the macroscopic mechanical properties of recycled concrete at the same time.The experimental results indicated that:with the recycled coarse aggregate replace rate increased the compression strength and resistance to chloride permeability of recycled concrete decrease.Extending the curing age can contribute to increasing the compressive strength and resistance to chloride permeability, and the amplitude of increased was relevant to the mix methods and recycled coarse aggregate replace rate.2.The linear correlation between recycled concrete compressive strength and chloride ion resistance, the results show that the compressive strength at 28 day and 60 day is poor, but electric flux and compressive at 28 day have a certain correlation which conforms to second multinomial approximately.3.The influence different recycled coarse aggregate replacement rates, bending stress levels, mineral admixtures and load ages have on the chloride ion penetration resistance performance of recycled concrete was investigated individually by a stress loading device designed by research group. The results showed that with the increase of recycled coarse aggregate replacement rate, diffusion coefficient would increase. While with the increase of bending stress level, the impact mineral admixture type has on the diffusion coefficient of chloride ion decreased. And the influence bending load has on the recycled concrete with 100% recycled coarse aggregate replacement rate was remarkably bigger than that with 50%. Therefore, the main influencing factor of chloride ion penetration resistance performance of recycled concrete is bending stress level. It was also found that depth of penetration showed well linear relation with square root of loading soak age.4.0n the basis of existing chloride diffusion model of current normal concrete and the test results of this paper, preliminary fitting the chloride diffusion model of recycled concrete which consider recycled coarse aggregates replacement rate and loading stress level, and preliminary estimating the working life of recycled concrete in chloride environment by empirical formula. The results show that:both improving the mixing method and adding mineral admixture can improve the durability of recycled concrete on different degree.