Damage extent and distribution in masonry surfaces subjected to salt crystallization due to moisture movements

A great amount of research has been done to study chemical and physical decay of porous materials (brick, stone, and mortar) in aggressive environment, therefore their mechanism of failure is well known. Nevertheless the decay of masonry as a whole, i.e. the influence of mortar joints behaviour on bricks and stones has not been considered enough as a matter of research. The experience of the authors has suggested to study the masonry surface decay due to the environmental condition not only through accelerated ageing tests in laboratory but also on site. The study on site of the decay caused by aggressive agents on existing building is always very difficult. This is due to the impossibility both of following the damage from the beginning and of measuring directly on the surface the level of damage and its progress along the time. For this reason some full-scale models were built and used as on site laboratory. In the environment the masonry deterioration is a process affected by a large randomness. Therefore, the authors have approached it stochastically. The aim of this approach is to obtain information on the durability of masonry material over time and/or on the prediction of a given damage level. This analysis is useful in the planning of maintenance and repair strategies. In accordance to this approach, a simple probabilistic model is proposed.