Some considerations about the durability of historic mortars

Abstract

The current manuscript discusses the durability of historical mortars. The majority of the descriptions about those mortars are mainly related to the Roman period and refer the mixture of calcium hydroxide and pozzolans (volcanic ashes and calcined clays) as the right recipe to get strong and durable binders. Those descriptions lack explanations about the reaction mechanisms that could explain the durability of those mortars, not can they explain the presence of analcime zeolites that several researchers found in historical mortars. The present manuscript discusses the durability of historical mortars trough the alkali-activation theory, according to which geopolymeric compounds and calcium silicate hydrates are responsible for the durability of historical mortars.