Safe Environments is able to determine the resistance of stone and other masonry materials to salt attack; the damage that is caused by salt residue left behind to crystalise in the pores of stone and other masonary materials.
In further detail, salt attack occurs when salt is transferred to stone and masonary materials through water that may be carried in the various surrounds of the material. When the water is evaporated the salt residuals are deposited in the pores of the masonry material. Over time this reoccurrence of wetting and drying cause a slow increase of salt in the pores and capillaries of the material resulting in a more concentrated salt remnant. At this time crystals will form, which gradually grow causing granules from the masonry to expand, thus exerting internal forces and stresses which may lead to damage to the stone or masonary material.
Masonry units, segmental pavers and stone pavers are common used in the built environment for their durability, low maintenance, and aesthetics. However, none of these materials are entirely salt safe with exposure to elements, such sea spray in coastal regions. Salt water swimming pools are another example of places that contain stone and masonry pavers that are subject to repetitive soaking and drying in salty water.
The degree of damage caused by salt attack depends on several variables and can range from chipping, exfoliation of surfaces, efflorescence damage to caviation, crumbling, and cracking, all of which can lead to the complete disintigration of the stone or masonary material. The type of salt the material is exposed to, the severity of the attack, and the period of time that the masonary has been in this particular state can all contribute to salt attack.
Safe Environments are able to conduct tests to determine a stone or masonary material's resistance to salt attack. Stones and other masonry units are tested according to two different methods of the AS/NZS 4456.10:2003, both of which test by subjecting the materials to cycles of soaking in salt solution and then a period of drying.
During these periods of wetting and drying, crystals that were dissolved in the salt solution attach themselves to the small pits within the stone. They then grow as the stone is subjected to drying and wetting again. Throughout this repetitive procedure the stones resistance to the salt attack is determined, and flaws or changes in the appearance of the material, as well as loss in weight of the stone are recorded.
Samples of stone or other masonry material can be sent to Safe Environments for salt attack testing. Materials should be sent in five separate units, each a cube with sides being 50±2mm in length free of chips and ribs.