Development of a new accelerated salt crystallization test

TNO Built Environment and Geosciences has developed, in cooperation with other institutes in the European project Compass, a new accelerated salt crystallization test. In this paper the design process leading to the definition of this test is described. Preliminary tests studying the influence of the environmental conditions on the damage development showed that the use of a high, but still realistic, temperature can enhance salt damage. The use of wet-dry cycles was found to be more effective than a continuous immersion of the specimens in salt solution. Experiments on different substrate/plaster combinations pointed out the relevance of the pore size of the system for the occurrence and type of decay: a coarse porous substrate may lead to faster damage to the plaster than a fine porous substrate. On the basis of the results obtained from this preliminary research a new accelerated test has been developed. The developed test procedure has been used in the crystallization experiments performed in the COMPASS project and has been proven to be effective even for the so-called "salt resistant" plasters.