Microtextural and microchemical studies of hydraulic ancient mortars: two analytical approaches to understand pre-industrial technology processes

Two different analytical approaches have been taken into account to investigate the role of Si-rich phases in enhance hydraulic reactions of bedding mortar mixtures from San Lorenzo Church in Milan (Northern Italy) and from the Medicean Aqueduct in Pisa (Central Italy). In the first case, mortars show clear hydraulic type reactions in the form of coronal layers between the reacting additive and the binder mass. In the second one, the hydraulic reactions do not develop visible mineral phases and processes have been inferred from chemical, mineralogical analyses and mass balance calculation. The microstructural studies not always are sufficient to understand the complex dynamics of reaction attained during pre-industrial manufacturing processing of mortars and related binders. In fact, if the reacting raw materials are fine-grained and/or have remarkable chemical reactivity, no relicts are preserved by mortar microtextures.