Pore structure in mortars applied on restoration Effect on properties relevant to decay of granite buildings

Since mortars play a key role in buildings decay, their suitable choice is critical to the success of restoration projects. The focus of this paper is to characterise the pore structures of a set of mortars and correlate them with mechanical properties and vapour permeability, which are relevant to the decay of granite buildings. Water vapour transport was tested by means of a simple set-up developed in our laboratory. A good correlation was found between total porosity and the two parameters tested: strength and vapour diffusivity. Pore size distribution also showed a strong influence on diffusivity. A mix based on cement with a high sand proportion was considered as the most suitable for granite building restoration because it showed good mechanical properties and low free calcium content. A negative aspect was that this mix exhibited significantly lower vapour permeability than mortar containing lime; this could be explained by the smaller radius of its pores.

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