Development of Half-Sandwich Panels with Alkali-Activated Ceramic and Slag Wastes: Mechanical and Thermal Characterization

This paper presents the development of two solutions for sandwich panels composed of a thin-layer alkali-activated composite (AAc) layer and a thicker insulation layer, formed by extruded polystyrene foam or expanded cork agglomerate (panels named APXPS or APICB, respectively). The AAc combined ceramic waste from clay bricks and roof tiles (75%) with ladle furnace slag (25%), activated with sodium silicate. The AAc layer was further reinforced with polyacrylonitrile (PAN) fibers (1% content). The mechanical behavior was assessed by measuring the uniaxial compressive strength of cubic AAc specimens, shear bond strength, pull-off strength between the AAc layer and the insulation material, and the flexural behavior of the sandwich panels. The thermal performance was characterized by heat flux, inner surface temperatures, the thermal transmission coefficient, thermal resistance, and thermal conductivity. Mechanical test results indicated clear differences between the two proposed solutions. Although APXPS panels exhibited higher tensile bond strength values, the APICB panels demonstrated superior interlayer bond performance. Similar findings were observed for the shear bond strength, where the irregular surface of the ICB positively influenced the adhesion to the AAc layer. In terms of flexural behavior, after the initial peak load, the APXPS exhibited a deflection-hardening response, achieving greater load-bearing capacity and energy absorption capacity compared to the APICB. Finally, thermal resistance values of 1.02 m2 °C/W and 1.14 m2 °C/W for APICB and APXPS were estimated, respectively, showing promising results in comparison to currently available building materials.