A review on the deterioration of cement-based materials in ammonium salt solutions

Abstract

It is essential to understand the durability aspects as the cementitious systems exposed to agricultural zones, fertilizer plants, waste waters, mining and industrial applications can be subjected to chemical attack by ammonium based compounds. This paper reviews the different mechanisms of deterioration of cement composites on exposure to different ammonium compounds namely ammonium sulphate, nitrate and chloride. The magnitude and mechanism of degradation follows different trends depending on the type of anion associated with the ammonium salts. The principle process involved in the deterioration of cementitious systems in the presence of ammonium compounds is the chemical reaction of portlandite with the anion of the ammonium salts. Generally the interaction of ammonium salts with cement based materials results in decalcification, leaching and/or expansion accompanied by strength loss. The presence of Supplementary Cementitious Materials (SCMs) along with cement reduces the amount of portlandite which may be attributed to the dilution of cement component or increased pozzolanic activity, resulting in the production of additional or secondary C-S-H gel. It is observed that the incorporation of SCMs is found to have low penetrability, thus capable of controlling the degradation process upon exposure to ammonium based salt solutions.