Water repellent influence on salt crystallisation in masonry

Abstract

This paper assesses the effectiveness and effects of a water repellent (sodium methylsiliconate in aqueous solution) on crystallisation in stone and brick masonry materials. The salt crystallisation method adopted in this study is based on capillary rise, concentration by evaporation and consequent crystallisation and prevention of efflorescence by surface treatment. The results confirm that cryptoflorescence (salt growth within pores) is considerably more damaging than efflorescence (salt growth on surfaces). They also provide strong evidence that treatment with sodium methylsiliconate can have a harmful effect on masonry materials and may promote their decay by suppressing the capillary transport of water and salt solution to the surface, thus forcing the formation of cryptoflorescence.

This paper assesses the effectiveness and effects of a water repellent (sodium methylsiliconate in aqueous solution) on crystallisation in stone and brick masonry materials. The salt crystallisation method adopted in this study is based on capillary rise, concentration by evaporation and consequent crystallisation and prevention of efflorescence by surface treatment. The results confirm that cryptoflorescence (salt growth within pores) is considerably more damaging than efflorescence (salt growth on surfaces). They also provide strong evidence that treatment with sodium methylsiliconate can have a harmful effect on masonry materials and may promote their decay by suppressing the capillary transport of water and salt solution to the surface, thus forcing the formation of cryptoflorescence.