Microscopic analysis of the deleterious effects of ammonium nitrate fertilizer on concrete

Abstract This paper presents a detailed study of parameters that makes concrete resistant to ammonium nitrate (NH4NO3) fertilizer attack. The major goal of this research work is to study the effect of ammonium nitrate on the strength and microstructure of silica fume (SF) composite concrete by performing microscopic testing techniques. X-ray diffraction (XRD) & Scanning Electron Microscopy (SEM) were used to study the mineral & chemical compositions of deteriorated samples. Cylindrical specimens were prepared by using silica fume as a partial replacement of cement i.e. 0%, 5%, 8%, and 10% in order to fulfill the requirement of impermeability of concrete specimens towards NH4NO3. The results show that compressive strength varies with the variation in SF content. Composite Concrete specimens for all percentages of SF were subjected to a 5% solution of NH4NO3 and its deleterious effect on concrete was accelerated using alternate wetting and oven drying cycles. SEM and XRD results showed the production of calcium nitrate as a product of deterioration. It is concluded that concrete samples with SF content of 8% have shown significant improvement in strength and more resistant to the NH4NO3 attack as compared to the other samples.