Synergistic reinforcement of foamed concrete using industrial waste stone powder and graphene oxide: Multi-scale characterization and field validation

Foamed concrete (FC) is a promising lightweight material for sustainable construction, yet its widespread application is often hindered by low mechanical strength and high water absorption. This study proposes a synergistic modification strategy using industrial waste stone powder (SP) and nano-graphene oxide (GO) to enhance the performance of FC for subgrade applications, especially in projects involving retaining walls where conventional heavy fillers would significantly increase wall construction costs. Although adding GO raises material costs, the use of low-cost SP and the reduction in retaining wall expenses offset this increase. A series of mix designs were evaluated, incorporating SP as a partial cement replacement (5–20%) and GO as a nano-reinforcer (0.01–0.05%). The results demonstrate that while SP improves dry density through micro-filling, its strength benefit is limited by a dilution effect at higher replacement levels. However, the addition of GO significantly offsets this limitation. The optimal composite, containing 10% SP and 0.03% GO, achieved a compressive strength of 2.15 MPa—a 68% increase over plain FC—while simultaneously reducing water absorption. Microstructural analysis via XRD, TGA, and SEM-EDS revealed that GO acts as a potent nucleation site for hydration products and facilitates the uniform dispersion of SP particles, leading to a denser and more homogeneous matrix. Field trials on an expressway subgrade confirmed that the modified FC exhibits superior stability, with interface earth pressures (≤0.05 MPa) and settlements (≤6 mm) significantly lower than traditional fillers. This research provides a robust, multi-scale framework for valorizing industrial by-products into high-performance, sustainable construction materials.