Di-ammonium hydrogen phosphate for the consolidation of lime-based historic mortars - Preliminary research

The paper investigates the use of di-ammonium hydrogen phosphate (DAP) as a possible consolidation treatment for lime-based mortars. Different DAP concentrations are proposed, additional post-treatment limewater application is used on some specimens. The results of application were evaluated in terms of mechanical property modification (dynamic elastic modulus, weight loss due to the peeling test), penetration depth, consolidant's distribution, colour change and water transport properties. Newly-precipitated phosphate-based phases were detected after the treatment and the relation towards treatment modality (i.e. DAP solution molarity and further limewater application) was evaluated. In the case of mechanical improvement, the outcomes indicate that a phosphate-based treatment is highly promising for mortar consolidation. Some non-negligible colour change was detected as a result of DAP application.