Effect of salt crystallisation on the shear behaviour of masonry walls: An experimental study

Salt weathering is one of the most common deterioration mechanisms in porous materials and may lead to severe damage in buildings and artworks. In last decades, a lot of research has been devoted to explain the mechanisms of crystal growth and crystallisation pressure inside pores and their relation with crack propagation in materials such as natural stone, brick, mortar and concrete. However, the effect of salts on the structural behaviour of masonry has not been fully elucidated. This paper presents a preliminary experimental study conducted on masonry specimens made of fired-clay bricks and cement mortar joints in order to assess the structural damage induced by salts. To this aim, the specimens were subjected to purposely-designed accelerated weathering procedures of different duration in sodium chloride and sodium sulphate solutions (the most common salts in brick masonries). Then, the shear behaviour of the artificially damaged masonry specimens was investigated by means of an ad hoc experimental test. As well known, the shear behaviour of masonry buildings plays a crucial role for structures located in areas prone to seismic hazard. The main mechanical parameters that result from the analysis of the pre-peak behaviour of the specimens, such as initial stiffness and peak load, have been correlated to the main material microstructural parameters (total porosity and pore size distribution) and to salt amount. It has been observed that the presence of salt affects the structural behaviour of masonry depending on the type of salt and on the duration of the weathering cycles. (C) 2012 Elsevier Ltd. All rights reserved.