Use of brick dust to optimise the dewatering process of hydrated lime mortars for conservation applications

Abstract

The impact of dewatering on lime mortars modified using brick dust was studied, as it is of particular importance in conservation applications. Dewatering takes place when freshly mixed mortars come into contact with a porous substrate, such as brick or stone, during on site construction. Since the dewatering process between the mortar and its substrate can modify the mortar properties, understanding the dewatering process enables pozzolan-modified hydrated lime mortars to be optimised for the masonry units being bonded. Evaluation of the water transport kinetics on brick dust—hydrated lime binder systems demonstrated their more water releasing behaviour. Investigations of non-dewatered and dewatered specimens in the volume ratio of 1:1:2 (lime:brick dust:sand) showed that the addition of brick dust to lime mortar increased dewatering, which in turn led to greater compressive strength, carbonation depth, decreased porosity and depth of water penetration. These properties are of great importance in the conservation of historic masonry, as mortars that are too strong or possess low permeability can accelerate degradation. This study will enable identification of the most suitable mix designs thereby increasing the durability and prolonging the life of historic masonry.