Weathering of limestone building material by mixed sulfate solutions. Characterization of stone microstructure, reaction products and decay forms

This paper presents a multidisciplinary approach to characterize, at both micro- and macro-scales, the behavior of a limestone widely used as construction material in South Spain when interacting with single- and mixed sulfate solutions of differing concentrations. A salt crystallization test that depicts the reality occurring in bottom walls of buildings was used to establish the related decay morphologies and weathering mechanisms. A systematic chemical, mineralogical, petrographic and porosimetric analysis of the fresh and weathered stones, the crystallized salts, and the evolution of ion concentrations of the solutions was performed. Factors controlling the type of fluid transport within the stone and its eventual breakdown were investigated and discussed. Concentrated solutions caused the most intense damage through chemical weathering and crystallization of salts causing a disrupting effect. Simple solutions caused more salt damage than did mixed solutions. This information will enable long-term predictions of material behavior and stone deterioration in buildings.