Influence of structural cracks in concrete on transport properties and chloride-induced corrosion of steel reinforcement

• Main Author: Wang, Junjie
• Published: Queen's University Belfast 2015
• Subjects: 620.1
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676607

Chloride-induced corrosion of steel in reinforced concrete structures is one of the main problems affecting their durability, but most previous research projects and case studies have focused on concretes without cracks or not subjected to any structural load. Although it has been recognised that structural cracks do influence the chloride transport and chloride induced corrosion in reinforced concrete structures, there is little published work on the influence of microcracks due to service loads on these properties. Therefore, the main objective of this research was to identify to what extent microcracks due to structural loads affect the chloride transport and chloride-induced corrosion in reinforced concrete structures and thereby make recommendations for any change of service life designs of such structures. Three stages of experiments were carried out. They were the influence of stresses and microcracks on chloride migration, diffusion, sorption and chloride-induced corrosion of steel in concrete. The main findings from this project are: chloride migration coefficients of concrete changed little when the stress level was below 50% of the ultimate stress (fu). A recovery of around 50% of the increased chloride migration coefficient was found in the case of concretes subjected to 75% of the fu when the load was removed. The influence of concrete mixes on chloride diffusion coefficient of concrete could be more significant than that of stress levels when the concrete was subjected to ponding of salt water. The role of cracks was found to be more important when the concrete was subjected to 'sorption + diffusion' compared with concrete subjected to diffusion alone. These finds suggest that the effect of microcracks is very significant for the service life of reinforced concrete structures in aggressive environments. This means that for the service life design of reinforced concrete structures in chloride exposure environments, consideration should be given to microcracks at service loads.