The Effect of Composition of Roman Cement Repair Mortars on Their Salt Crystallization Resistance and Adhesion

Crystallization of soluble salts in porous networks is a major source of decay for mortars used in historical buildings. The optimum formulation and application of Roman cement mortars which could produce compatible and durable repairs of the original substrates was studied. Measurements were performed with the aim of determining the pore size distribution, the hydric parameters as well as the salt crystallization resistance of the mortars. The adhesive strength of the repair materials laid on historic substrates was also determined. The results of the crystallization tests show that repair Roman cement mortars with hydric parameters close to those of the historic substrates, though different pore size distributions, have related salt crystallization resistance.