There are number of areas where cement composites can be exposed to ammonium based compounds such as agricultural land, chemical fertilizer plants, waste waters, polluted and industrial environments, which can induce severe and premature deterioration of concrete systems. Based on the review of literature, the most common and deleterious ammonium based salts were found to be ammonium nitrate, ammonium chloride and ammonium sulphate. The cementitious systems with Ordinary Portland Cement (OPC) may be attacked easily by these ammonium based chemicals as the OPC hydrates such as Portlandite and C-S-H gel are considered to be unstable in these aggressive media. Thus, it is necessary to understand the alteration kinetics of cementitious systems and the effectiveness of Supplementary Cementitious Materials (SCMs) in improving the resistance when exposed to ammonium based environments for develpoing more durable and sustainable concrete systems. The aim of this experimental study was to investigate the durability aspects in terms of the changes in mechanical properties of cement mortar specimens made with OPC and different combinations of various Supplementary Cementitious Materials (SCMs) exposed to ammonium based salt solution prepared using chemical grade ammonium chloride (NH4Cl). The mortar specimens were exposed to ammonium chloride solution in two different concentrations (1.25 M and 2.5 M) for a maximum exposure duration of two and half months. The SCMs used for the study include Class F Fly ash (FA), Ground Granulated Blast Furnace Slag (GGBS), and Silica fume (SF). The changes in the mechanical properties were evaluated on the basis of visual assessment, depth of penetration, changes in the compressive strength, changes in Ultrasonic Pulse Velocity (UPV) and relative dynamic modulus of elasticity. From all the test results, it can be concluded that the ternary blended mix with OPC, GGBS and Silica fume (OPC-GGBS-SF) has higher resistance to ammonium chloride attack. The results stress the need to include SCMs and the importance to tailor make the concrete for structures exposed to aggressive environment like ammonium chloride.

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.