Diffusivity of Chloride Ion in Mortar Cubes Made Using Ordinary Portland and Portland Pozzolana Cements

Abstract

Cement is subject to degradation by aggressive media. This study investigated chloride diffusivity in mortar made from Kenyan cements which included three brands of Ordinary Portland Cements (OPC) and three brands of Portland Pozzolana Cements (PPC) sampled within Kenyan markets. The test cements were used to make mortar prisms at different water/cement ratios. Compressive strength was determined at the 7th and 28th day of curing. The mortars were subjected to laboratory prepared 3.5 % by mass of sodium chloride solution under accelerated ion migration test method for a period of thirty six hours using a 12V DC power source. The compressive strength before subjecting to aggressive media was found to increase with curing duration as well as on decreasing w/c. Compressive strength at all w/c ratios was found to increase after the aggressive media ingress. After subjecting the mortar cubes to Cl- media, they were sliced and the cores from the slices analyzed for Cl- content. From these results, Dapp was approximated from solutions to Fick’s 2nd law using the error function. PPC at all w/c ratios showed lower Dapp than OPC. Cl- ingress for both cement types across all cement categories, increased with the increase in w/c ratio.