Chloride diffusion in the cracked concrete

The diffusion of chloride is affected by the cracks in the concrete materials. The influences of cracking width on the chloride diffusion coefficient and diffusion surface are discussed in this paper. The chloride diffusion coefficient of concrete varies with the cracking widths, and there exist upper and lower limitations. The effect of cracking on the chloride diffusion can be divided into three cases: 1) when the width is less than 0.03mm, its effect can be neglected due to self-healing; 2) when the width is more than 0.1mm, two-dimensional diffusion will happen in the cracking zone; 3) and when the crack width is between 0.03 and 0.1mm, chloride diffuses into concrete along and perpendicular to the crack surface simultaneously. Formula for chloride diffusion in these three cases were brought forward, and an calculation example was given ac- cording to the analysis of this article. The results of calculation agree well with the test, which can provide a reference to the design of concrete durability. 1 INTRODUCTIONS gress in concrete under different conditions of load-induced cracks. All these models considered Chloride is a very important factor which influences the crack width’s effect. The chloride content in the durability of concrete structures in their service the cracked zone increases as crack width in- life. It can induce the steel corrosion and concrete creases. cover cracking. Ingress of chloride in the concrete However, many tests found that crack had no in- was studied since 1970’ (Collepardi1972, Buenfeld fluence on the chloride ingress when crack width et al. 1987, Boddy 1999, JIN 2007). Many useful were below a specific value, and crack width repre- conclusions have been gotten about this. But only a sented similar influence on chloride penetration few of them considered the crack’s effect.