Effect of calcium leaching on the pore structure, strength, and chloride penetration resistance in concrete specimens

Abstract

In radioactive waste repositories constructed underground and on shorelines, concrete members can remain in contact with groundwater for a long period. However, even pure water creates concentration gradients which lead to the diffusion of Ca ions from the pore water and the degradation of the underground concrete. Therefore, the purposes of this study are to investigate not only the alteration of the pore structure and the loss of compressive strength associated with dissolution but also the characteristics of chloride penetration after leaching-related degradation.The results show that as the leaching period increases, the volume of pores with diameters ranging from 50nm to 500nm is greatly increased. Also, pores larger than 200nm in size rapidly increase in number during the initial leaching time, while those smaller than 200nm increase in number only gradually. Furthermore, the residual strength of the leached part with OPC ranges from 35% to 60%. In addition, those of the mineral admixture replacement ranged from 23% to 50%. The chloride diffusion coefficient measured by the chloride profile increased two-to-five-times with the leaching duration.