Quantifying the Fly Ash Dividend: A Cradle-to-Gate Life Cycle Assessment of M30 Concrete Paver Blocks under Indian Sourcing Conditions

A cradle-to-gate LCA of six M30 paver block mixes was executed in openLCA v1.11 with Ecoinvent 3.8 and ReCiPe Midpoint (H) under Indian sourcing conditions. The principal conclusions are: (i) Cement production is the overwhelming environmental hotspot, contributing ≈ 87% of GWP for the control and ≈ 80% for the optimum sustainable mix. No aggregate-side intervention, in isolation, can meaningfully reduce cradle-to-gate impact. (ii) Class F fly ash at 10% of OPC is the principal decarbonisation lever, delivering 8.1–11.6% GWP reduction, 6.3–12.7% fossil energy savings, 7.3–12.2% PM reduction, and 5.9–10.9% water-use reduction per block. Scaled to infrastructure: 8,276–8,393 kg CO₂ eq. saved per km of paved road. (iii) C&D waste substitution in isolation produces near-zero change in cradle-to-gate impact (< 0.12% GWP variation). Its sustainability value lies in landfill diversion and virgin-aggregate conservation — benefits outside the cradle-to-gate boundary. (iv) Filtering through IS 15658:2021 mechanical compliance, three of the six mixes — including the highest-environmental-benefit mix — are undeployable. M30-FA10-RCA0 is the overall optimum (40.8 MPa CS, 4.68 MPa FS, 8.1% GWP reduction). M30-FA0-RCA15 is the waste-diversion optimum (≈ 35 tonnes of unprocessed C&D waste per km of paved road, full compliance retained). The study provides the first openLCA-based environmental benchmark for M30 paver block production under Indian sourcing conditions that explicitly couples LCA outcomes with IS 15658:2021 compliance.

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