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Problem Statement
Accurate determination of concrete slab thickness and assessment of underlying conditions are critical for evaluating the structural integrity and service life of built infrastructure. Traditional coring methods are invasive, time-consuming, and often compromise the structure. A non-destructive and high-resolution approach was required to measure slab thickness, detect reinforcement, and identify potential voids beneath the structure.
Overview
A Ground Penetrating Radar (GPR) survey was conducted using a 500 MHz broadband antenna (250–750 MHz) to measure the thickness of a reinforced concrete slab and assess subsurface anomalies.
Engineering Impact
Enabled non-destructive thickness measurement of reinforced concrete structures.
Identified reinforcement conditions and spacing with high clarity.
Provided early detection of subgrade cavities, supporting preventive maintenance and rehabilitation planning.
Reduced the need for invasive coring, saving time and preserving structural integrity.
Conclusion
This study highlights the effectiveness of GPR with a 500 MHz broadband antenna for slab thickness evaluation and subsurface assessment. The ability to resolve reinforcement, underlying strata, and cavities establishes GPR as a reliable tool for condition monitoring and structural health evaluation in civil infrastructure.
Methodology
System Configuration: 500 MHz antenna with ultra-wide bandwidth for shallow, high-resolution imaging.
Survey Design: Closely spaced parallel profiles were collected to generate 2D sections and depth slices.
Processing Workflow: Standard GPR data processing, including filtering, migration, and amplitude analysis, was applied to refine thickness estimation and anomaly mapping.
Key Findings
Slab Thickness Measurement: Clear reflection signatures allowed accurate estimation of concrete slab thickness.
Rebar Detection: Strong hyperbolic signatures of reinforcement bars were visible due to the high-frequency content in the shallow region of the slab.
Underlying Strata: Distinct layering below the slab was imaged, providing insights into subgrade composition.
Cavity Detection: Possible voids or cavities were detected beneath the reinforcement slab, indicating potential risk zones.
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