Structural Capacity Enhancement of Geosynthetic-reinforced Asphalt Overlays: Full-Scale APT Evaluation and Design Implications

Abstract

Geosynthetics are commonly used in pavement systems to mitigate reflective cracking; however, their potential contribution to improving the structural capacity of asphalt overlays has not been fully quantified. This study evaluates the structural benefits of geosynthetic paving interlayers using full-scale instrumented pavement models tested in an Accelerated Pavement Testing (APT) facility. Asphalt strain gauges were used to monitor tensile strains under repeated wheel loading. By quantifying stable response parameters such as tensile strain reduction, rutting rate reduction, and modulus Improvement Ratio (MIR), this work provides the experimental and analytical foundation required for the development of simplified design modification approaches. The geogrid-reinforced section exhibited reductions of approximately 38% in cumulative plastic displacement, 38% in rut depth, and over 50% in tensile strain at the bottom of the distressed asphalt layer compared with the unreinforced section. These reductions indicate an apparent increase in the modulus of the asphalt layer, quantified through a MIR of 2.85. The experimentally derived MIR, which is product specific, temperature and interface condition dependent, was incorporated into an empirical pavement design framework based on the AASHTO 1993 methodology, allowing the structural benefits to be translated into design parameters such as increased structural number (SN) or reduced asphalt thickness. A design example indicated that the reinforced system could result in a 32% reduction in asphalt thickness for a design traffic of 30 million standard axles. Findings highlight the potential of geosynthetic paving interlayers not only for reflective cracking mitigation but also as a structural reinforcement mechanism capable of improving pavement performance and enabling more efficient pavement designs.