Synergistic Effect and Enhancement Mechanism of Foam Concrete Composites by Incorporating Aerogel, Hollow Glass Microspheres and Nano-Silica

Aerogel-incorporated foam concrete has attracted significant attention in the construction sector owing to its light weight and superior thermal insulation properties. Nevertheless, its practical application in external wall insulation systems is hindered by the high cost of aerogel (AG) and the inherent trade-off between thermal efficiency and mechanical strength. To overcome these limitations, this study introduces a composite design that partially replaces AG with low-cost hollow glass microspheres (HGMs) and incorporates nano-silica (NS) as a strengthening agent. Foam concrete specimens with a constant dry density of 700 kg/m3 were fabricated with these additives. Through an orthogonal experimental approach, the synergistic effects of AG, HGMs, and NS on mechanical properties, porosity, water absorption, and durability were systematically evaluated. The results demonstrated that 4% AG content significantly reduced effective porosity by 33% and water absorption by 59%, while 4% HGM increased compressive and flexural strength by 13.5% and 19.7%, respectively. The addition of 2% NS further enhanced mechanical performance, yielding 25.9% and 21.6% improvements in compressive and flexural strength. The optimal formulation (A4H4N2) effectively balanced thermal insulation and mechanical properties, offering a viable strategy for producing cost-effective, high-performance foam concrete suitable for building envelope applications.