Infrasense Gets to the Bottom of Pavement Thickness

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Infrasense has recently performed subsurface pavement thickness investigations on sections of the Pennsylvania Turnpike. The newly completed work represents Infrasense's second pavement thickness analysis project on the Pennsylvania Turnpike in as many years. The objective of the work is to reduce the number of cores required by the turnpike authority to characterize the pavement.

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Vehicle setup for pavement thickness survey using GPR

Infrasense, Inc. recently completed a subsurface pavement thickness investigation on sections of the Pennsylvania Turnpike using ground penetrating radar (GPR). This work was part of a new 2-year multi-phase effort and included determination of asphalt and concrete pavement thickness over 66 directional miles of composite pavement structure. The objective of the work was to investigate the possibility of reducing the number of cores that the turnpike authority typically uses to characterize its pavement structures. Thickness data was collected with a single air-coupled radar antenna, and was synchronized with a Global Positioning System (GPS) to provide coordinate locations for the detected pavement thicknesses. Data collection was performed at normal highway speeds with a single shadow vehicle, allowing traffic to flow without any disruption.

Infrasense has played a key role in the development and implementation of GPR for pavement assessments over the past 25 years. Currently, the most common application of this state-of-the-art technology is the determination of pavement layer thickness because, unlike traditional coring, GPR requires no lane closures and provides a timely and cost-effective means of collecting continuous thickness data. This data may be used for network-level pavement management, project-level rehabilitation design, or quality assurance of newly constructed pavements. Infrasense surveys have covered over 10,000 lane miles of pavement. Projects range in size from our recent project in Pennsylvania to a survey of 3,500 miles for the Oklahoma Department of Transportation.

At the network level, GPR can provide layer structure data used to identify homogeneous sections and to compute the remaining life of segments of the network. Computation of remaining life enables highway agencies to optimize their programming and planning of pavement rehabilitation. A number of agencies have implemented GPR at the network level, including the California Department of Transportation (CalTrans) and the Oklahoma DOT.

At the project level, GPR data provides information that enables owner agencies and consultants optimize rehabilitation design by providing accurate information on the current pavement structure. GPR data is also used to implement pavement recycling by providing details on the thickness of the bound material and how it varies over the project length.

Many GPR pavement thickness studies focus on supporting FWD operations. Pavement strength evaluations using a Falling Weight Deflectometer (FWD) provide useful data to pavement engineers for estimating remaining life and planning rehabilitation. Accurate pavement layer thickness data enhances FWD pavement strength evaluations, since thickness data is required for calculation of the pavement moduli. Thus, the availability of GPR data can provide a better estimate of the remaining life of a particular pavement and can enable more accurate planning decisions.

Layer thickness estimates are also useful for quality assurance/quality control (QA/QC) for construction of new pavements and overlays. GPR can provide a faster, nondestructive and more complete means of obtaining QA/QC data then coring. Inadequate layer thickness can be quickly identified, and construction pay factors may be determined.

About Infrasense, Inc.
Since 1987, Infrasense, Inc. has applied the most current technologies to the most difficult challenges in subsurface scanning. Infrasense’s engineers are able to nondestructively extract critical information from a diverse range of structures. The firm has conducted research to advance the field of subsurface detection, while also providing valuable information to clients across the country. Learn more about Infrasense, Inc. and its services at


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Ken Maser
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