Sustainable stabilization of sandy soil using alkali-activated construction waste binders

This study explores the sustainable stabilization of sandy soil using alkali-activated binders derived from construction and demolition waste (CDW), including waste concrete powder (WCP), waste brick powder (WBP), and waste tile powder (WTP). The binders were activated with a binary solution of NaOH (6 M) and Na₂SiO₃ (SiO₂/Na₂O = 2.5) and applied at dosages of 5–20 wt%. Mechanical performance was evaluated through unconfined compressive strength (UCS), durability under wet–dry and freeze–thaw cycles, and microstructural analyses (XRD, FTIR, SEM/EDS). A cradle-to-gate life cycle assessment (LCA) benchmarked environmental impacts against ordinary Portland cement (OPC) stabilization. Results showed that WTP achieved the highest strength (UCS up to 6.76 MPa at 28 days), followed by WBP (6.55 MPa), while WCP exhibited limited reactivity (~ 1.14 MPa). WTP-based mixtures retained their strength after ten wet–dry cycles but lost ~ 25% after freeze–thaw exposure, whereas WBP and WCP suffered more severe deterioration (40–63% loss). Microstructural evidence confirmed the formation of N–A–S–H and hybrid gels, correlating with mechanical outcomes. LCA revealed a substantial reduction in global warming potential (32.5 vs. 182.2 kg CO₂-eq·t⁻¹ for OPC), although NaOH production remained the main hotspot. These findings highlight the potential of CDW-based alkali-activated binders as eco-efficient alternatives for sandy soil stabilization, supporting both engineering performance and circular economy goals.