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Problem Statement
In transportation and pavement engineering, accurate knowledge of asphalt overlay thickness is essential for structural capacity assessment, maintenance planning, and rehabilitation design. Traditional coring is destructive and provides only point-specific data. A non-destructive, high-resolution solution was required to evaluate the asphalt layer and underlying concrete slab, along with potential anomalies at their interface.
Overview
A Ground Penetrating Radar (GPR) survey was performed using a 500 MHz broadband antenna (250–750 MHz) to measure the thickness of asphalt overlay placed over a concrete base and to assess the condition of underlying strata.
Engineering Impact
Delivered non-destructive thickness evaluation of both asphalt and concrete layers.
Provided a continuous pavement profile beyond point-specific coring methods.
Enabled early detection of debonding and voids, supporting preventive maintenance planning.
Reduced investigation time and preserved pavement integrity.
Conclusion
This case study demonstrates the utility of GPR for layer thickness measurement and interface assessment in asphalt-over-concrete pavements. The ability to resolve asphalt thickness, concrete slab conditions, and potential anomalies makes GPR a powerful diagnostic tool for pavement engineering and infrastructure management.
Methodology
System Configuration: 500 MHz broadband antenna for shallow high-resolution imaging of pavement layers.
Survey Design: Parallel lines with dense spacing were acquired for both 2D radargrams and 3D volumetric reconstruction.
Processing Workflow: Filtering, migration, amplitude analysis, and depth conversion techniques were applied to quantify layer thicknesses and highlight anomalies.
Key Findings
Asphalt Thickness Measurement: The asphalt overlay thickness was mapped with high accuracy based on clear dielectric contrast between asphalt and concrete interface.
Concrete Slab Imaging: Underlying concrete slab thickness was also estimated, providing a complete pavement profile.
Interface Characterization: The asphalt–concrete contact zone was clearly delineated, allowing detection of potential debonding or moisture ingress.
Anomaly Detection: Reflections indicated possible air gaps, voids, or material deterioration at localized points within the slab system.
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