Improving the performance of lime-sand finishing mixes

Abstract In many regions of the world, there are significant reserves of polymineral clays with a predominance of montmorillonite. Despite this, there is a lack of scientific research on the use of polymineral clays to modify and improve the properties of dry mortar mixes. The novelty of the article is to identify the scientific patterns of the influence of organomineral additives on the structure formation of wall finishing products. The organomineral additive based on polymineral clays with a high content of montmorillonite was prepared in the form of new composition, based on which dry mortar mix for interior decoration of walls of buildings with improved strength properties and operational characteristics was created. It was established that the adsorption of an organic additive promotes hydrophilization of the clay surface and an increase in its effective specific surface. The formulation of an organomineral additive for dry mortar mixes was developed, which promotes the adsorption of anionic and nonionic surfactants on the surface of polymineral clays with a high content of montmorillonite. In addition, the microstructural, morphological properties and XRD data of the researched materials were determined. The composition of the dry mortar mix designed for internal finishing work and containing lime, quartz sand fraction 0.63–0.16 and organomineral additive was developed. The following indicators characterize the finishing layer based on the developed mix: adhesive strength Radh = 0.60–0.76 MPa, cohesive strength Rcoh = 0.35–0.36 MPa, vapor permeability µ = 0.055–0.058 mg / m·h·Pa, conditional ratio crack resistance Ccr = 0.54–0.58, water absorption by weight Wm = 12.29–13.62%, elastic modulus E = 40–50 MPa, shrinkage deformation ɛ = 0.020–0.034%. The calculation in the SCAD Office software proved that the developed dry mortar mixes satisfy the crack resistance conditions of the finishing composites and can be used for decorative interior decoration of building walls.