High-strength high-ductility Engineered/Strain-Hardening Geopolymer Composites (EGC/SHGC) incorporating dredged river sand

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The development of sustainable engineered geopolymer composites (EGC) with balanced mechanical performance and eco-efficiency remains a critical challenge. This study proposes a novel approach utilizing dredged river sand (DS), a waste byproduct from the dredging of waterways, as fine aggregates to fabricate EGC. Three EGC formulations with DS, river sand (RS), and silica sand (SS) were systematically investigated. The EGC with DS achieved a remarkable compressive strength of 169.1 MPa and tensile strain of 12.4 %, outperforming both EGC with RS (148.7 MPa, 11.1 %) and EGC with SS (163.8 MPa, 12.0 %). X-CT and microhardness tests revealed that the ultra-fine DS reduced the mean residual crack width of EGC to 84.1 μm (vs. 88.0 μm for EGC with RS and 91.8 μm for EGC with SS), thereby contributing to superior crack control and durability. Environmental and cost assessments demonstrated the sustainability advantages of the EGC with DS, exhibiting the lowest embodied carbon (2.6 kg CO₂/m³/MPa), embodied energy (12.1 MJ/m³/MPa), and cost per strength (6.5 CNY/m³/MPa), outperforming conventional aggregates. Comparative analysis with existing ultra-high-strength engineered cementitious composites (UHS-ECC)/EGC highlighted that EGC with dredged river sand successfully pushed the performance envelope of UHS-EGC. This study demonstrates the viability of dredged river sand as a sustainable, low-carbon alternative for advancing UHS-EGC, offering a sustainable pathway for repurposing dredging waste.