Experimental Comparison between Salt Weathering Testing Procedures on Different Types of Bricks

Abstract

Accelerated weathering tests are commonly carried out to evaluate the resistance of porous materials to the damage induced by salt crystallization. A wide range of testing procedures have been prescribed by various standards and recommendations to suit the spectrum of materials adopted in general construction. On account of the differences in the procedure and the reagents prescribed, the results of different tests are prone to be different even on the same material. In the current study, a remarkable difference in the severity and pattern of deterioration was observed when the same set of bricks were subjected to accelerated weathering tests prescribed by different standards’ recommendations. Although the deterioration was less severe and always occurred during the drying phases of the first standard, much more severe damage (with about fivefold greater mass changes) was observed during the rewetting phases of the second standard. Simple calculation showed that the concentration of ions furnished in the second standard’s test were about 62% greater than in the first standard’s test. Based on this and the occurrence of more severe damage in spite of drying at lower temperatures in the second standard’s test, different damage mechanisms are envisaged in the two tests. Although the damage in the first standard’s test may be predominantly attributed to evaporation-induced supersaturation, the occurrence of massive damage during successive immersions at room temperature suggests that it could be predominantly caused by dissolution-mediated phase transformation of thenardite to mirabilite in the second standard’s test. These hypotheses about the damage mechanisms presented in the study are mainly based on the qualitative differences between the damage manifestations upon exposure to sodium sulfate solution as per the studied standards’ tests.