Multi-objective optimization of thermal and mechanical properties of lightweight foam concrete with Binary Blend of fly ash and silica fume

This study systematically optimizes lightweight foam concrete (LWFC) formulations to balance thermal insulation and mechanical strength, which is critical for sustainable construction. Using the Taguchi method, sixteen mix designs were evaluated for compressive strength, density, and thermal conductivity, incorporating fly ash (FA), silica fume (SF), detergent, and sugar as key variables. Results reveal that optimal FA (30 %), and SF (15 %) enhance compressive strength by 18 % through pozzolanic reactivity and microstructural densification, confirmed via Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) analyses. While higher detergent content (>8 %) increases porosity, reducing strength and thermal conductivity, moderate sugar (4 %) improves workability without sacrificing lightweight properties. The optimized mix (435 kg/m³ binder, 30 % FA, 15 % SF, 8 % detergent, 4 % sugar) achieves a low density (1487 kg/m³), exceptional thermal insulation (λ: 0.29 W/m·K), and relatively high mechanical performance for its density class, demonstrating its viability for energy-efficient building applications. This work provides actionable insights for designing eco-friendly LWFC with tailored properties, addressing both structural and thermal demands in modern construction.