Crystallization of sodium sulphate in polymer impregnated plasters

The common occurrence and harmful effects of sodium sulphate make it a major cause of deterio- ration in plasters. The investigation conducted showed that a plaster composed of eminently hydraulic lime impregnated with water-repellent solutions (a perfluoropolyether or an oligomen’c alkylalkoxysiloxane) or admixed with an acrylic latex is significantly more durable than plain plaster. In particular, the different modes of salt crystallization are discussed in relation to the microstructural properties conferred by the poly- mers, and to the thermohygrometric conditions of the system.