Effects of cold joint and loading conditions on chloride diffusion in concrete containing GGBFS

RC (Reinforced Concrete) structures undergo deterioration and the initiated corrosion in the steel is considered as one of the most critical problems. For efficient construction of structures, construction joint should be installed, however cold joint occurs reluctantly due to delayed concrete placing and poor condition of the old concrete surface. The chloride ingress in cold joint concrete is more rapid than that in sound concrete, and it is also affected by loading conditions. This paper presents a quantitative evaluation on chloride diffusion coefficient considering the effects of cold joint and loading conditions. For the work, concrete samples with 0.6 of w/b (water to binder) ratio are prepared. Compressive and tensile stresses are induced with 30% and 60% of ultimate strength, respectively. The chloride diffusion coefficients in accelerated condition are measured under loading, and the effects of cold joint and loading levels are evaluated. In order to investigate an effect of GGBFS (Ground Granulated Blast Furnace Slag) on chloride diffusion, 40% of GGBFS replacement ratio is considered for OPC (Ordinary Portland Cement) and the GGBFS effect is evaluated considering cold joint and loading levels. The effects of stress level, pore structure improvement through GGBFS, and cold joint on chloride diffusion coefficient are quantitatively investigated.