Mechanism of nitric acid attack on hardened paste ofgeopolymeric cements, in addition to the leaching process discussed in part I[1], consists of an electrophilic attack by acid protons on polymeric Si-O-Albonds resulting in the ejection of tetrahedral aluminium from thealuminosilicate framework. The framework vacancies are mostly re-occupied bysilicon atoms resulting in the formation of an imperfect highly siliceousframework that is relatively hard but brittle. The ejected aluminium convertedto octahedrally coordinated aluminium mostly accumulates in the intraframeworkspace.
