Utilization of Refused Derived Fuel (RDF) waste in cement-stabilized lateritic soil as a sustainable pavement base material

Municipal solid waste incineration generates Refuse-Derived Fuel (RDF) fly ash, a waste byproduct with pozzolanic potential. This research evaluates RDF fly ash utilization in cement-stabilized lateritic soil (LS) as pavement bases through systematic comparison of two implementation strategies: partial cement replacement versus supplementary addition. Comprehensive testing assessed mechanical properties (UCS, ITS), microstructure (SEM, XRD), and environmental safety (TCLP). Results reveal distinct performance characteristics. The addition approach achieved progressive strength enhancement: 2.71 MPa UCS and 0.29 MPa ITS at 28 days (30% RDF fly ash), exceeding control (2.57 MPa, 0.24 MPa). Conversely, the replacement approach indicated strength reduction: 2.19 MPa UCS and 0.18 MPa ITS at 30% replacement – 14.8% and 25% below control, respectively. Strong linear correlation between 7-day and 28-day UCS (R 2 > 0.94) enables accelerated quality assessment, while UCS-ITS correlation (R 2 = 0.80) allows complementary property prediction. Microstructural analysis revealed the mechanisms underlying performance differences. Addition-method specimens exhibited dense C-S-H networks, C-A-H phase development, and refined pore structure. Replacement specimens showed progressive porosity increase and depleted cementitious phases. TCLP testing confirmed all heavy metals (As, Cd, Cr, Cu, Hg, Pb, Zn) below detection limits (0.01-0.05 mg/L). This dual-strategy investigation validates RDF fly ash functions effectively as a supplementary cementitious material when adequate primary cement is maintained. Findings advance sustainable waste valorization in pavement infrastructure.