Engineering geogrid enabled low carbon and aggregate efficient flexible pavements

As the world emphasizes sustainable infrastructure, the pavement sector is under pressure to minimize material utilization and environmental footprint while maintaining functionality. Flexible pavements are mainly responsible for consuming virgin aggregates and related carbon emissions. Reinforcement with geosynthetics, notably geogrids for flexible pavements, provides an effective route to managing these challenges through improved structural efficiency and material savings. This study comprehensively evaluates the impact of geogrid reinforcement on the structural and environmental performance of flexible pavements constructed over relatively soft subgrades with California Bearing Ratios (CBR) of 2%, 5%, and 10%. By systematically varying the geogrid axial stiffness between 400 and 1500 kN/m, a series of advanced 3D finite element simulations were conducted using PLAXIS 3D, with validation against field plate load test data to ensure model reliability. Optimal geogrid placement depths were identified for each subgrade condition-at H/4 and H/3 (H = total thickness of granular layer) from the top of the granular layer for CBR values of 2% and 5%, respectively, and at the base-subbase interface for CBR 10%, demonstrating the significance of tailored reinforcement approaches. The findings witnessed Modulus Improvement Factors (MIF) ranging from 1.3 to 3.0, correlating directly with geogrid stiffness and contributing to substantial reductions in pavement layer thickness, 15-30% for asphalt and granular layers. These reductions enhance material efficiency and result in a 6-24% reduction in carbon footprint, highlighting the double advantage of geogrid application in structural optimisation and environmental sustainability. Field verification proved in good agreement with simulations, with the deviations in settlement being less than 10%, affirming the reliability of the numerical method. This study gives practical advice for integrating geosynthetic reinforcement in pavement design (mechanistic), encouraging resource-saving construction methods, and contributing to the worldwide move toward low-carbon infrastructure solutions.