Physico-chemical and mechanical characterization of hydraulic mortars containing nano-titania for restoration applications

In this work nano-titania of anatase and routile form has been added in mortars containing: (a) binders of either hydrated lime and metakaolin, or natural hydraulic lime and, (b) fine aggregates of carbonate nature. Mortar composition was tailored to ensure adhesion of fragments of porous limestones from the Acropolis monuments. The aim was to study the effect of nano-titania in the hydration and carbonation of the above binders, as well as the mechanical properties and the adhesive capability of the designed mortars, where the nano-titania proportion was 4.5–6% w/w of binder. The physico-chemical and mechanical properties of the nano-titania mortars were studied and compared to the respective ones, without the nano-titania addition. DTA-TG, FTIR, SEM and XRD analyses indicated the evolution of carbonation, hydration and hydraulic compound formation during a 1 year curing. Results indicate enhanced carbonation, hydration and modulus of elasticity of mortar mixtures with nano-titania. A specifically designed experimental procedure for measuring the direct tensile strength of the mortar–stone system proved that nano-titania mortars can be used as adhesive materials for porous limestones.