Water Absorption and Microbial Corrosion Resistance of Hemp Concrete Modified with the Acid Casein Admixture

The hemp-lime composite is a material with high porosity; therefore, it has a high ability to absorb water. Long-term contact of the composite with water is a destructive factor for the material due to the content of organic components and the lack of a hydraulic binder. It is important to look for ways to modify the composition of the composite in order to reduce water absorption. In traditional old construction, acid casein was used to improve the strength and water resistance of lime mortars. In this study, the influence of the admixture of casein in the amount of 1, 3, 5% of the binder mass on the water absorption and capillary rise of the hemp-lime composite was examined. Both the content of shives and the admixture of animal origin may contribute to the development of biological corrosion, which is why microbiological tests were performed on composite samples using the impression and swab method. As the casein content increased, the water absorption of the composite was reduced. The rate of capillary rise and the amount of rising water were also reduced. The addition of casein limited the ability to absorb water without significantly increasing the susceptibility to the development of microorganisms. The research should be extended to include, among others: the influence of this admixture on the composite's vapor permeability and mechanical properties.