Lime-based mortars with added silica fume and bioproducts for restoration and preservation of heritage buildings

Abstract

Restoration of heritage buildings requires an appropriate choice of materials, as inappropriate materials can lead to degradation rather than preservation. Hydrated lime and sand mortars are the most suitable for masonry cladding. However, they have low durability regarding current requirements. This work investigates the use of silica fume and/or biopolymers (egg albumen and additive derived from the reuse of milk unfit for human consumption (complexes of whey protein with κ-casein) in producing these mortars. Some mortars were characterized by mechanical properties (compressive and diametric strength, absorption rate) and chemical properties (SEM, Infrared spectrum). The research revealed that silica fume addition allows an increase of more than 50% in the mechanical strength of the mortars when associated with animal protein. The value may be higher than 60%, especially for biopolymers (complexes of whey protein with κ-casein). Finally, the proteins in the mortar mixture provide intense air entry that results in the formation of more pores. This increase in voids allows more CO2 to enter, directly contributing to a faster carbonation process and performance mortar.