Assessment of the Type of Paint on Performance of Rendering Mortars

Abstract

The aim of this work is to determine how the mechanical and physical properties of render mortars, in particular their moisture performance, are affected by the application of paint. In this study, three commercial paints, hydro-pliolite-based paint, acrylic paint and silicate paint, were applied as coating layers on render mortars formulated with different binders. The choice of the binders used (hydrated lime, natural hydraulic lime and cement) was related to the functional requirements that the renders have to fulfil according to the type of buildings where they are applied (i.e., new or old buildings). Firstly, the hardness and surface cohesion of the different painted and unpainted renders were analysed in order to investigate the effect of the type of paint on the mechanical strength of the render surface. The influence of the paints on the moisture behaviour of the renders was then investigated using the water capillarity test, the water vapour permeability test and the drying test. The results show that all the paints studied can cause a significant change in the behaviour of the renders in terms of moisture transport phenomena. Nevertheless, it can be concluded that acrylic paint has the greatest resistance to water absorption, but it is also the paint with the higher resistance to water vapour diffusion. Hydro pliolite paint was found to be adequate from the point of view of reducing moisture accumulation and is the most recommended for old buildings with hydrated lime or hydraulic lime-based renders.