Journal of Civil Engineering (IEB), 36 (1) (2008) 23-42 Simulation of chloride ion profile into repaired crack concrete Md. Shafiqul Islam and Md. Mahmud Sazzad Department of Civil Engineering Rajshahi University of Engineering and Technology, Kazla 6204, Rajshahi, Bangladesh Received 10 September 2007 _____________________________________________________________________ Abstract Chloride induced corrosion of steel in concrete is a threatening problem in coastal and marine environment. The durability of structures decreases and hampers efficient structural performance. In reality, cracks are often generated at cover concrete. In that case, the transportation of chloride ion (Cl - ) may take only a few hours to reach the steel, while transportation through uncracked concrete would take a longer time. Moreover, if some part of concrete is repaired by polymer modified cementitious mortar, the transportation of Cl - ion is affected by the combination of two different materials. In this study, experiments were done with partially repaired crack concrete to simulate real field structure. A model is proposed to calculate the concentration profile inside a partially repaired crack concrete with the help of a 2-dimansional FORTRAN program. © 2008 Institution of Engineers, Bangladesh. All rights reserved. Keywords: Chloride, diffusion, transport properties, cracking 1. Introduction Chloride induced corrosion of steel in concrete structures, affected by deicing salt, coastal and a marine environment is a great problem everywhere in the world. A considerable number of structures cease to function adequately. Extensive research was conducted over the past decades to study the transport properties of concrete. The disadvantage is that all predictions are carried out considering a ‘perfect’ and uncracked concrete. The fact that most reinforced concrete structures having cracks are often ignored (Pettersson and Sandberg 1997). Once these cracks take place, the transport properties of material change drastically and it is no longer reasonable to assume that durability life-span based on uncracked properties will hold. A debate among the researchers on crack width and corrosion rate relationships has been continuing for a long time. Several researches found little relationships between crack width and corrosion rate (Schweitzer 1986).