Optimizing Sustainable Rigid Pavement Concrete: Structural Performance, Carbon Reduction, and Cost Efficiency with Fly Ash and GGBS

The construction industry's dependence on cement contributes heavily to global carbon emissions, necessitating sustainable alternatives for rigid pavement. This study investigates the partial replacement of ordinary portland cement with flyash and ground granulated blast furnace slag (GGBS) to develop an eco-friendly concrete mix that maintains structural performance. Present study systematically evaluated cement properties—fineness, consistency, setting times, soundness, and compressive strength—at five single replacement levels for flyash (6%–30%) and GGBS (3%–27%), followed by five combined replacement levels (e.g., 6% flyash with 3% GGBS). Concrete cubes of M40 grade were cast and tested at 28 days. The results demonstrate that moderate combined replacement, specifically 18% flyash with 15% GGBS, achieved a compressive strength of 38.03 MPa, closely approaching the control mix's 41.05 MPa. Moreover, this combination reduced carbon emissions by approximately 53% (from 369.14 kg/m³ to 173.90 kg/m³) and lowered material costs by about 25% (from ₹5160 to ₹3840 per m³). Higher replacement levels, however, led to significant strength reductions, with the 30% flyash and 27% GGBS combination yielding only 29.22 MPa. The novelty of this work lies in establishing an optimal balance between structural integrity, environmental sustainability, and economic viability for rigid pavement concrete. It is concluded that strategic use of flyash and GGBS can transform pavement construction practices by addressing waste management and carbon footprint challenges simultaneously, thereby offering a practical pathway toward greener infrastructure.