A synergistic use of waste glass and waste rhododendron in green foamed concrete: from fresh behavior to durability

The increasing demand for sustainable construction materials has driven the exploration of alternative binders and aggregates in lightweight concrete systems. This study investigates the mechanical, physical, thermal, and durability performance of foamed concrete produced using waste glass powder as binder and rhododendron as aggregate. A total of 12 mix designs were prepared by adjusting the ratios of glass powder and rhododendron, while maintaining a consistent water-to-binder ratio and foam content across all samples. Fresh properties, including flow diameter and fresh unit weight, were evaluated, followed by tests on compressive and flexural strength at 7, 28, and 91 days. Physical characteristics such as oven-dry unit weight, porosity, water absorption, and thermal conductivity were determined. Durability assessments encompassed drying shrinkage, capillarity, high-temperature resistance (200–700 °C), freeze–thaw cycles (up to 100 cycles), and sulfate resistance after 60 days of exposure to MgSO₄. Microstructural changes were characterized using Scanning Electron Microscopy (SEM). The results indicate that the combined use of glass powder and rhododendron enhances thermal insulation and sustainability while maintaining sufficient mechanical performance. Mix G15R10 demonstrated the most balanced properties across all tests, combining low thermal conductivity and acceptable strength and durability. SEM analysis revealed microstructural densification with glass powder and highlighted the role of Rhododendron in modifying pore structure and interfacial zones. This research underscores the viability of incorporating organic waste and industrial by-products in foamed concrete as a sustainable solution for lightweight construction.