Effects of ammonium phosphate as a consolidating agent on cementitious surfaces

Abstract

Salt scaling is responsible for much of the damage that occurs to concrete surfaces in cold weather climates. Although treatments exist that attempt to prevent or reduce damage, none directly address the glue-spall mechanism responsible for salt scaling. The goal of this project was to form a protective layer of hydroxyapatite on a cementitious surface that would increase its resistance to salt scaling. This was done by treating cement paste surfaces with two different ammonium phosphate solutions. Experiments included using various forms of microscopy and chemical analysis to explore the reaction between ammonium phosphate solution and cement, in addition to indentation and freeze-thaw experiments to evaluate the physical effects of the reaction. The results indicated that both diammonium hydrogen phosphate and triammonium phosphate were successful in reacting with cement to form hydroxyapatite, and that both were successful in increasing the hardness of sample surfaces. Additionally, samples treated with triammonium phosphate solution