Porous lightweight aggregates enable multifunctional solid waste-based foam composites with tailored pore structures for sustainable construction

Conventional foam composites rely on a single foam-generated pore system, which causes an intrinsic trade-off between thermal insulation and acoustic absorption. Their performance has largely plateaued and no longer satisfies the increasing demands for sustainable building envelopes. In this study, hierarchically porous artificial lightweight aggregates (ALA) were fabricated from solid waste-based binders using a core-shell encapsulation strategy coupled with chemical foaming, and subsequently incorporated into a physically foamed matrix to develop multifunctional lightweight aggregate foam composites (LAFC). Theoretical modeling and experimental characterization show that the pore characteristics of the aggregates significantly influence the overall pore size, uniformity, fractal dimension, tortuosity, and connectivity. Moreover, a structural compensation effect between the matrix and aggregate phases governs the functional enhancement of LAFC. Benefiting from graded porosity and physicochemical internal curing, ALA-modified composites exhibit pronounced improvements in flexural strength (+25.14%), thermal insulation (+16.12%), and shrinkage resistance (+17.46%) relative to plain foam composites, while achieving a substantially higher noise reduction coefficient (NRC, +67.65%) compared with ceramsite-based LAFC. A carbon footprint assessment further reveals a reduction of up to 31.34% compared to expanded perlite-based LAFC, attributable to the use of waste-derived ALA. Pilot-scale trials further confirm their potential of achieving ultra-low thermal conductivity (0.057 W/(m·K)) combined with broadband acoustic absorption (NRC = 0.62). Mechanistic analysis reveals that ALA enhance multifunctionality by regulating matrix porosity, forming closed-cell and resonance-enabling structures, and generating multi-layer interfacial transition zones. This work provides an effective pathway for designing energy-efficient, noise-reducing construction materials through integrated pore and interface engineering.