Durability studies on blended cement paste exposed to ammonium chloride environment

Abstract

The exposure of concrete systems in ammonium based environments can be considered as an aggressive medium which can induce severe and premature deterioration, thus adversely affecting the durability of concrete structures. This paper aims to understand the degradation kinetics of cementitious systems made with Ordinary Portland Cement (OPC) and various combinations of Supplementary Cementitious Materials (SCMs) exposed to chemical grade ammonium chloride (NH4Cl) solution. For this study, the cement paste specimens were exposed to ammonium chloride solution in two different concentrations (1.25 M and 2.5 M) for an exposure duration of two and half months. The kinetics of degradation were evaluated on the basis of changes in mass, visual assessment, changes in thickness and changes in the pH of ammonium chloride solution. Based on the test results, the ternary blended mix with OPC, Ground Granulated Blast Furnace Slag (GGBS) and Silica fume (SF), that is, OPC(50%) - GGBS(40%) - SF(10%) is found to have higher resistance to ammonium chloride attack. The results stress the need to include SCMs and the importance to tailor make the cementitious system for structures exposed to aggressive environment like ammonium chloride.