Design-Based Assessment of Hybrid Thermal-Insulating Dry Plaster Mortars for Aerated Concrete Walls in Aral Sea Region Conditions

Abstract

The paper presents a design-based assessment of thermal-insulating dry plaster mortars intended for aerated concrete and other porous wall materials under the dry, windy and salt-aerosol affected conditions of the Aral Sea region. The study focuses on the simultaneous compatibility of the plaster layer with the porous substrate in terms of thermal resistance, vapour permeability, capillary water absorption, adhesion and crack resistance. Five mortar variants were compared: a reference cement-sand plaster, perlite-based and vermiculite-based lightweight plasters, a hollow-microsphere modified plaster and a hybrid perlite-vermiculite-microsphere composition. A multi-criteria approach was used to evaluate the balance between low thermal conductivity, sufficient compressive strength, low water absorption and vapour-open behaviour. The calculated screening indicators show that the hybrid composition can reduce thermal conductivity to 0.116 W/(m·K), decrease capillary water absorption to 0.26 kg/(m²·h⁰·⁵), and maintain adequate adhesion to aerated concrete. The results confirm that the best solution is not the composition with the lowest density alone, but the one that combines closed and open pore systems with a compatible lime-cement matrix and hydrophobic modification. A minimal laboratory testing program is proposed for further verification before pilot application.