<p>The article presents the results of comprehensive experimental studies on the properties of slag-alkali foam concretes produced without Portland cement. Granulated electrothermophosphorus slag, mechanically activated in a ball mill, was used as the main aluminosilicate component. The physical, mechanical, structural, and thermal characteristics of the specimens were analyzed, including average density, compressive strength, moisture content, water absorption, microporosity, and thermal conductivity coefficient. The influence of fine sand content on the formation of the porous structure and the performance characteristics of the foam concrete was investigated. The addition of sand was found to increase density and reduce moisture content, while slightly decreasing compressive strength. Microporosity analysis revealed that sand addition decreases the average pore diameter while increasing the total pore volume. The thermal conductivity coefficient of the specimens ranged from 0,11 to 0,18 W/(m·K), depending on moisture conditions, which meets the requirements for modern thermal insulation materials. The obtained results confirm the feasibility of producing slag-alkali foam concrete using non autoclaved technology while maintaining satisfactory strength and thermal insulation properties. The use of such materials contributes to reducing CO₂ emissions and conserving natural and energy resources, thereby promoting the development of environmentally friendly and energy-efficient building materials. Keywords: slag; alkali-activated binder; foam concrete; average density; compressive strength; thermal conductivity; water absorption; microporosity.</p>