Mechanistic evaluation of geosynthetic interlayer performance in asphalt overlays: Effects of temperature, loading rate, and placement depth

Abstract

Reflective cracking remains a critical challenge in bituminous pavement rehabilitation. This distress occurs when existing cracks in the underlying pavement propagate upward through the asphalt overlay, compromising rehabilitation durability and necessitating repeated maintenance interventions. Geosynthetic interlayers offer a promising solution for mitigating this problem, but their effectiveness depends on multiple factors that have rarely been studied systematically. This thesis presents a mechanistic evaluation of three geosynthetic interlayer types - a paving fabric (PF), a carbon-glass fiber geogrid (Carbophalt GB), and a fiberglass geocomposite (Glasphalt GV) - using a crack widening device developed at ÉTS. This device enables rapid, reproducible assessment of crack resistance in reinforced bituminous systems using compact specimens (80 mm × 80 mm × 80 mm). The experimental program systematically examines the effects of temperature (-20 °C, 25 °C, and 40 °C), loading rate (2 and 5 mm/min), and placement depth (one-third, one half, and twothirds from the specimen bottom), with the full rate-depth factorial conducted at 25 °C and 40 °C. Performance parameters include stiffness indices (K0-4mm and K̄ 10 30%), energy dissipation, Toughness Improvement Factor (TIF), fracture energy (GIC), and interfacial J-integral. The results show clear behavioral differences among materials. Paving fabric delivers stable performance with low rate-sensitivity (TIF of 1.36-1.54 at 2 mm/min and 1.08-1.21 at 5 mm/min), attributable to progressive fiber activation that enables effective energy absorption across both displacement rates. Glasphalt GV shows strong rate sensitivity: poor performance at 2 mm/min (TIF of 0.54 - 0.57) reverses to excellent performance at 5 mm/min (TIF of 1.12- 1.29), indicating its glass fiber network requires dynamic loading for effective activation. Carbophalt GB shows moderate, stable performance (TIF ≈ 1.0). One-third depth placement consistently outperforms other positions across all materials and conditions, enabling early crack interception and effective stress redistribution before significant damage accumulates in the upper asphalt layer. Unreinforced specimens achieve higher stiffness but exhibit brittle failure, whereas reinforced systems trade stiffness for ductility - precisely the intended function of geosynthetic interlayers. At elevated temperature (40 °C), reduced asphalt viscosity limits force development despite increased deformation capacity. The interfacial J-integral analysis confirms that paving fabric at one-third depth requires the highest energy for crack propagation, validating its superior crack resistance. A supplementary pull-out investigation revealed that the bolt-clamped configuration induced tensile-tearing failure of the geotextile rather than interface debonding, providing lessons for future bond-strength testing protocols. A finite element model calibrated against the measured response reproduced the peak force, the peak displacement, and the dissipated work within 3 percent. An exploratory correlation framework between monotonic and cyclic fatigue loading parameters was developed using log-linear regression on three consistent material datasets, providing a diagnostic tool for anticipating fatigue ranking from faster monotonic tests. This research provides practical recommendations for interlayer selection and placement: paving fabric for general applications across variable traffic conditions, Glasphalt GV only for high-speed dynamic loading environments, and one-third depth placement for all geosynthetic types. The findings also show that laboratory testing protocols should incorporate multiple loading rates, as single-rate testing may misrepresent field performance.

Date	4 Sept 2026
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Alan Carter (Supervisor), Michel Vaillancourt (Co-supervisor) & Eshan Dave (Co-supervisor)