Hydraulic lime mortars for the restoration of historic masonry in Crete

This study presents the results of the physico-chemical characterization of original mortars and plasters and the evaluation of the repair ones prepared with natural hydraulic lime (NHL) as binding material and siliceous sand and crushed brick as aggregates. The repair mortars were applied in restoration works of a historic masonry in Crete, Greece. The proportions of binder, aggregates and water were selected in order to achieve optimum workability. Original mortars, containing magnesian lime, had to be replaced since previous interventions with cement-based mortars have provoked damage acceleration. Water absorption by capillarity, compressive strength, modulus of elasticity, porosity and pore size distribution were determined at early stages and after 1 year of curing time; these properties prove the suitability of the proposed mortars for such an application. After 3 years of intervention with NHL-based mortars and plasters, macroscopic survey and analyses of the applied materials reveal that no cracks or release of soluble salts occur.