The Study Of Chloride Ions Penetration Capacity And Critical Content In Concrete

In this paper, it was mainly studied that the penetration capacity and critical content of chloride ions in concrete with different water/binder ratio, fly ash and slag under immersion and cycle of dry and wet conditions.The relationship of chloride ions diffusion coefficient with time conforms to power function according to chloride ions' content in each layer of different concrete. Based on the relationship, a mathematical model equation of chloride ions diffusion in concrete was deduced as follow:Test results show that chloride ions diffusion coefficient decreases with the water/binder ratio reducing. When fly ash or slag is properly blended, chloride ions diffusion coefficient will also drop. Chloride ions diffusion coefficient is related with test conditions, the diffusion coefficient in cycle of dry and wet conditions is always larger than that in immersion conditions.In this paper, rebar corrosion state was judged with three electrochemical nondestructive measuring technologies, i.e. half-cell potential, A.C. impedance and time potential. When the rebar was transformed from passivation to depassivation, it can obtain the chloride ions corrosion critical content through taking and analyzing chloride ions content around the rebar. Test results show chloride ions critical content in immersion conditions is always larger than that in cycle of dry and wet for the same concrete, that is, test conditions affects chloride ions critical content value. In the same conditions, water/binder ratio obviously affects chloride ions critical content, but the influence of fly ash or slag on chloride ions critical content is not obvious.It is obtained the equation that chloride ions critical content change with water/binder ratio through linear fitting experiment data.The studied results also show A.C. impendence spectrum not only can quicklyand exactly judge the rebar state in concrete, but also hardly disturb the work electrode, in addition, much message of the concrete and rebar surface can be obtained. Therefore, A.C. impendence technology is a promising method in studying the rebar corrosion state in concrete.