Utilization of Building Demolition Waste Materials for Sustainable Granular Sub-Base Design: Experimental Characterisation, ANN-Based Prediction and Life-Cycle Cost Assessment

Building demolition waste can be converted into technically acceptable GSB material when blended with suitable aggregate fractions. BW-GSB alone satisfied most physical requirements but its 24.8% soaked CBR was below the desired threshold, so direct unblended use is not recommended for structural GSB. The 50:50 S1-C3 mix achieved 36.5% soaked CBR, 1.948 g/cc MDD and 0.52 MPa UCS, making it a balanced Grade I option. The multi-material S3-C3 mix (50% BW-GSB, 10% Conventional GSB, 20% RBA, 20% CTW) achieved 40.1% soaked CBR and the highest UCS of 0.68 MPa—the best sustainable experimental mix. ANN predictions agreed strongly with experiments (R² = 0.932 for soaked CBR, 0.983 for MDD), supporting data-driven preliminary screening. In pavement design, S3-C3 required only 325 mm GSB thickness versus 300 mm for conventional GSB, and life-cycle cost analysis showed the GSB road to be the lowest-cost option, saving 48.97% over bitumen and 62.11% over concrete. Overall, demolition-waste GSB can support sustainable, cost-effective and structurally reliable flexible-pavement construction. Future work should include repeated-load triaxial testing for resilient modulus and permanent deformation, field trial sections, leachate and geo-environmental assessment of CTW and mixed waste, larger datasets for ANN and hybrid optimisation, expanded life-cycle assessment covering embodied carbon and transport sensitivity, and performance-based specifications for demolition-waste GSB under Indian conditions.  

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