Infrasense Performs Ground Penetrating Radar (GPR) Survey of Pavement Structure near East Greenwich, Rhode Island

In early April, Infrasense conducted a non-destructive survey and report for 10 lane miles of a section of Route 2, in Rhode Island.  The project provided the client with 4 sets of data showing where concrete appears to be present under the asphalt pavement versus an aggregate base.  The survey was conducted at driving speed with no closures, no disruption to traffic, and zero impact to the integrity of the road. 

The GPR data collection system included a pair of 1 GHz horn antennas and a SIR 30 control unit, both manufactured by GSSI in the United States.  The final report included a quantitative table of segments or roadway defined by mile posts along by 4 different wheel paths, along with visual plots showing the structure type along the 5- mile stretch.

The GPR pavement surveys are carried out according to ASTM D4748-10. The resulting data shows a cross-sectional slice of the pavement strata at various offsets. Each slice includes the surface, and any material change in the first few feet below the surface.

Infrasense Carries out Ground Penetrating Radar (GPR) and Infrared Thermography Evaluation of Pavement Structure in District 5, Idaho

This past summer, Infrasense conducted a multi-faceted non-destructive survey and report for 84 lane miles of a section of I-86, made up of abutted concrete panels.  The project provided the client with a comprehensive set of condition results to identify and map out distressed panels along the roadway. Surveys were performed at normal driving speed with no disruption to traffic.

The GPR data collection system included a pair of 1 GHz horn antennas and a SIR 30 control unit, both manufactured by GSSI in the United States.   The infrared survey was performed using a FLIR camera mounted on top of the survey vehicle along with a 4K high resolution visual feed for reference.  The final report included a quantitative table of deterioration, delamination, cracking, spalling, repaired/replaced panels, and panels recommended for replacement.  Infrasense provided plan-view maps of their findings, along with a quantities summary table providing quantitative figures for each mile of each lane.

The GPR pavement surveys are carried out according to ASTM specifications. The resulting data shows a cross-sectional slice of the pavement strata at various offsets. Each slice includes the surface, the top mat of reinforcing steel, and the bottom of the slab. The amplitude of these layers is calculated and then quantities and maps of concrete deterioration and concrete cover are produced. The resulting maps are provided in both PDF and CADD compatible formats.

The infrared surveys were carried out according to ASTM specifications. The infrared data is reviewed simultaneously with the video data to differentiate delaminated areas from surface features (discoloration, oil stains, sand and rust deposits, etc.) that appear in the infrared, but are unrelated to subsurface conditions. Subsurface delaminations produce a thermal barrier and result in higher surface temperatures as the sun heats up the surface. These higher temperature areas are detected with the infrared camera, and subsequently quantified and mapped.

Nondestructive Evaluation of Bridge Decks in North Carolina

Infrasense and BDI recently teamed to perform a unique study of three bridges in Davie County, North Carolina for the North Carolina Department of Transportation (NCDOT).  The objective of the study was to pilot a comprehensive NDE testing program on a small sample of bridge decks, which will be used as a basis for future larger-scale implementation as part of the SHRP2 R06A Implementation Assistance Program.  The testing program included ground penetrating radar (GPR), infrared thermography (IR), high-resolution video (HRV), BDI’s deck acoustic response system, SounDAR, manual chain drag, chloride ion penetration, and rebound hammer.

Infrasense was first on the scene to carry out the high-speed GPR, IR, and HRV surveys. This survey was performed with a vehicle mounted dual horn GPR antenna system mounted off the rear of the survey vehicle and an infrared camera and high resolution video camera system mounted side by side on the roof.  This system allows for the collection of three complete datasets, which are all triggered by a wheel-mounted distance encoder. The surveys were carried out at highway speed, allowing traffic to flow uninterrupted. The analysis of the GPR, IR, and HRV data was carried out using Infrasense’s proprietary software and resulted in quantities and plan-view maps of deterioration, delamination, spalling, patching, and rebar cover.

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Shortly after, BDI carried out a suite of NDE tests including manual chain drag, chloride ion penetration, and rebound hammer; as well as a recently developed method, SounDAR (Deck Acoustic Response).  SounDAR, developed by BDI, is a method that automates the cumbersome and time-consuming process of manual chain drag using a vehicle-mounted system. The system includes a series of chains, and other impact devices, along with corresponding microphones covering 8-feet of bridge width per driving pass. The recorded acoustic response is analyzed using a proprietary software to produce a delamination map. In addition to increased data collection efficiency, SounDAR has the advantage of being an objective measure, as opposed to manual chain drag which relies on onsite interpretation and varies significantly from inspector-to-inspector.

The results from this study showed good correlation between all of the methods for each of the three bridge decks. The prospective larger-scale NDE testing program will likely deploy a 2-phased approach, with Phase 1 including the driving speed methods to cover all of the decks in the program, followed by higher resolution inspection methods carried out on a subset of the decks based on the Phase 1 results and agency needs.

Infrasense Collects and Analyzes Thickness of Pavement Structure Layers on South Carolina’s I-85 Using Ground Penetrating Radar

In May 2017, Infrasense carried out a GPR pavement thickness survey of 24 lane-miles of I-85 near Spartanburg, SC.  The right shoulder, right lane, center lane, and left lane were surveyed in both northbound and southbound directions.  The results of the survey included a statistical summary of the pavement layer thicknesses in each lane, as well as a tabulated sheet of asphalt and base layer thicknesses reported every 5 feet with corresponding GPS coordinates.  The project provided the client with a continuous and comprehensive roadway profile to facilitate a data-driven approach rehab design efforts.

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The GPR equipment used for this survey was a single 1-GHz horn antenna and a SIR 20 control unit, both manufactured by GSSI in the United States.  The GPR data, collected at 1 scan per foot, was synchronized with a high-resolution differential GPS unit. This particular GPR system allows for collection at highway speeds, and can provide subsurface data to a depth of 3 feet.

How does it work?
Ground penetrating radar operates by transmitting short pulses of electromagnetic energy into the pavement using an antenna attached to a survey vehicle. These pulses are reflected back to the antenna with an arrival time and amplitude that is related to the location and nature of dielectric discontinuities in the material. The reflected energy is captured and may be displayed on an oscilloscope to form a series of pulses that are referred to as the radar waveform. The waveform contains a record of the properties and thicknesses of the layers within the pavement. For more info visit: http://www.infrasense.com/gpr-pavement-thickness/

Infrasense Carries out Ground Penetrating Radar (GPR) and Infrared Thermography (IR) Condition Surveys of 17 Bridge Decks in Wisconsin’s North Central Region

This past summer, Infrasense conducted a multi-faceted non-destructive survey and report for 17 bridge decks in Wisconsin DOT’s North Central Region.  The project provided the client with a comprehensive set of condition results to facilitate a data-driven approach to programming their bridge inventory. Surveys were performed at normal driving speed with no disruption to traffic.

The GPR data collection system included a pair of 2 GHz horn antennas and a SIR 30 control unit, both manufactured by GSSI in the United States.   The infrared survey was performed using a FLIR camera mounted on top of the survey vehicle along with a visual feed for reference.  The final report included a quantitative table of deterioration, debonding, patching, and spalled areas.  A select number of the decks were chosen by the client for further reporting, where Infrasense provided plan-view maps of their findings, along with ground-truth confirmation at suspect locations on the decks.  Finally, the report included an underside visual inspection summary, with pictures and descriptions. 

 Final map of a bridge deck consisting of GPR, IR and sounding

Final map of a bridge deck consisting of GPR, IR and sounding

The GPR bridge deck surveys are carried out according to ASTM D6087-08. The resulting data shows a cross-sectional slice of the bridge deck at various offsets. Each slice includes the top of the deck, top mat of reinforcing steel, and the bottom of the deck. The amplitude of these layers is calculated and then quantities and maps of concrete deterioration and concrete cover are produced. The resulting maps are provided in both PDF and CADD compatible formats.

The infrared bridge deck surveys are carried out according to ASTM D4788-03 (2013). The infrared data is reviewed simultaneously with the video data to differentiate delaminated areas from surface features (discoloration, oil stains, sand and rust deposits, etc.) that appear in the infrared, but are unrelated to subsurface conditions. Subsurface delaminations produce a thermal barrier and result in higher surface temperatures as the sun heats up a deck. These higher temperature areas are detected with the infrared camera, and subsequently quantified and mapped.

Infrasense Welcomes New Employees

In 2017, Infrasense welcomed Aleksey and Patrick aboard as our two newest full-time employees! Aleksey and Patrick will be filling Geoscience Engineer and Staff Engineer roles, respectively. 

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Aleksey received his Ph.D degree in Geological Engineering from the Missouri University of Science and Technology (MS&T). During his postgraduate  studies, he was actively involved in multiple projects assessing condition of concrete and pavement structures using various geophysical methods.

Before signing on with Infrasense, Aleksey worked as a postdoctoral fellow at the Missouri MS&T. His primary research interests involved application of GPR for civil engineering problems. He also enjoyed teaching a variety of geophysical classes for undergraduate and graduate students.

When his work days are done, Aleksey loves spending time with his wife and daughter exploring Boston area. Also, he enjoys taking pictures that never appear online and baking bread & pastries.

Patrick received his Bachelor’s degree in Geoscience from the University of Massachusetts - Lowell. After graduating with honors, Patrick worked at a geoscience and geophysics consulting firm performing myriad geological and geophysical surveys. Recently, Patrick passed the Professional Geologist exam, adding another set of “P.G’ initials to his resume! His experience and knowledge with computers, electronics, geology, and geophysics has helped Patrick hit the ground running at Infrasense.

Outside the office, Patrick keeps busy with odd jobs such as repairing computers and phones, customizing cars, and taking care of his corals and exotic plants.

Evaluation of Pascack Road Bridge Deck in NY using Ground Penetrating Radar (GPR)

In order to facilitate rehabilitation planning of an asphalt overlaid bridge deck carrying I-87 over Pascack Road, ground penetrating radar (GPR) was used to quantify and map concrete deterioration.

The GPR data was carried out at driving speeds using a vehicle-based system, so no lane closures were required. In addition to being deployed at driving speeds, GPR has the ability to penetrate and detect deterioration through the full thickness of the deck, regardless of the presence of an overlay. The GPR equipment used for this survey was a dual 2-GHz air-coupled horn antenna system manufactured by GSSI, Inc. of Nashua, NH.

Evaluation of Pascack Road Bridge Deck in NY using Ground Penetrating Radar (GPR)

This bridge deck analysis was carried out according to ASTM D6087-08 using Infrasense's proprietary software, winDECAR® and was surveyed with 40 lines of GPR data, each representing a longitudinal cross-section through the deck. The cross-section shows the different structural layers of the bridge deck including the bottom of the asphalt overlay, top reinforcing steel, and bottom of the deck. The amplitude of these layers is calculated and then quantities and maps of concrete deterioration, asphalt overlay thickness, and concrete cover are produced. The resulting maps are provided in both PDF and CADD compatible formats.

Condition evaluation of Lafayette Road Bridge Deck with Ground Penetrating Radar (GPR) by Infrasense

Infrasense recently performed a ground penetrating radar (GPR) survey of the bridge deck carrying Lafayette Road over the Soo Line and B.N. Railroad in St. Paul, Minnesota. The GPR data collection system included dual 2GHz horn antennas and a SIR-30 control unit manufactured by GSSI of Nashua, NH. This GPR survey was carried out at normal driving speeds, with no lane closure or disruption to traffic. The results of the survey will be facilitate planning future maintenance rehabilitation efforts.

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The GPR data analysis was carried out according to ASTM D6087-08 using Infrasense's proprietary software, winDECARR. The analysis involves tracking the reinforcing steel and bottom deck reflections and calculating the concrete dielectric constant, rebar concrete cover, and concrete attenuation (loss of energy through deck). The results include quantities and maps of concrete deterioration and rebar-cover, and are provided in PDF and CADD compatible formats.

Ground Penetrating Radar (GPR) Evaluation of I-85 Shoulders from MP 98 to MP 106 in South Carolina

Infrasense recently carried out a subsurface pavement structure evaluation on 8 miles of Interstate 85 between Gaffney, South Carolina, and Grover, North Carolina. To determine the thicknesses of the pavement structure layers, ground penetrating radar (GPR) was used in the field testing program which included continuous data collection along the right shoulder in each direction of Interstate 85, from milepost 98 to milepost 106. The data was collected at driving speed, so traffic flow was not disrupted. The deliverables for this project included continuous layer thickness information provided in tabular and graphical formats. The results will be used as part of a rehabilitation design effort, and to ensure the shoulders can support traffic that is redirected during construction.

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The GPR equipment used for this survey included a 1GHz horn antenna and SIR-30 data acquisition system, both manufactured by GSSI of Nashua, NH. The 1GHz antenna is particularly well suited for pavement evaluations as it provides an optimum balance of resolution and depth of penetration. Using this equipment, and in-house analysis software, the GPR layer thickness results are typically within 10% of core thickness values.

Nondestructive Condition Evaluation of Main Street Bridge Over Chemung River in Elmira, New York by Infrasence

Infrasense has recently performed a condition evaluation of the bridge deck carrying Main Street over the Chemung River in Elmira, New York. The evaluation was carried out using infrared thermography (IR), ground penetrating radar (GPR), and high-resolution video (HRV) imaging.

The Infrared Thermography (IR) survey was performed according to ASTM D 4788 – 03 (2013) using the latest technology mounted to an elevated platform on top of the survey vehicle and operated remotely from within the vehicle. Data was collected with maximum temperature differentials caused by delamination. 
The IR and HRV input was compiled in a series of passes across the roadway area of the deck, moving at approximately 30 mph. The Main Street deck required two passes - one for each lane. Each pass covered a deck width of 15 feet while the IR and HRV cameras were connected to an electronic distance measuring instrument (DMI) for accurate location referencing.

Graphic - Falls Church Asphalt Thickness

The GPR surveys were completed according to ASTM D 6087-08. The survey included 11 lines of data for the roadway area and 3 lines of data for the two shoulder areas; each representing a cross sectional slice of the deck at a particular offset. The DMI distance data was continuously recorded into each GPR record, so that each GPR data scan had an associated distance.

The GPR evaluation of Pavement Network Located in Falls Church, Virginia

Infrasense recently completed the subsurface pavement structure evaluation of approximately 79.93 lane-miles of public roadways in Falls Church, Virginia using Ground Penetrating Radar (GPR) testing to determine the thicknesses of the pavement structure layers. It was performed along the centerline of each roadway, centerline of each lane, and at an offset approximately 1 foot from the outside edge of each lane. The resulting pavement structure information was integrated into the Falls Church Pavement Management System, and will be used for programming future rehabilitation efforts.

Graphic - Falls Church Asphalt Thickness

The survey was carried out at the posted speed limit for all roadways, and the entire Falls Church network was covered in only 3 days. The GPR data was collected with concurrent distance data via a wheel-mounted encoder and differentially corrected GPS data. GPR provides the benefits of being nondestructive, non-disruptive to the traveling public, and offers complete coverage. The pavement thickness measurements from GPR are typically found to be within 10% of core thicknesses.

Dr. Ken Maser Presented on Network-Level Pavement Structure Evaluation at the World Conference on Pavement and Asset Management (WCPAM)

  Dr. Ken Maser presented the results of a network-level pavement substructure evaluation completed in Idaho. The project focused on a network of 700 miles of roadways covering a wide range of geographic and pavement structure conditions. The roadways were continuously surveyed with a Traffic Speed Deflectometer (TSD) and with Ground Penetrating Radar (GPR). The TSD data was analyzed along with the associated GPR layer thickness data to determine subgrade modulus, pavement modulus, structural number, and remaining life. 

Dr. Ken Maser presented the results of a network-level pavement substructure evaluation completed in Idaho. The project focused on a network of 700 miles of roadways covering a wide range of geographic and pavement structure conditions. The roadways were continuously surveyed with a Traffic Speed Deflectometer (TSD) and with Ground Penetrating Radar (GPR). The TSD data was analyzed along with the associated GPR layer thickness data to determine subgrade modulus, pavement modulus, structural number, and remaining life. 

New 3D-GPR System Being Used on 2017 Projects!

Infrasense recently deployed an air-launched 3D-Radar system on projects in Iowa, Florida, and Virginia. The high-resolution system contains 21 antennas spaced 3 inches apart, and is capable of penetrating up to 5 feet below the surface. Infrasense has used this system to evaluate bridge deck, pavement, and tunnel deck conditions. 

2nd Annual Infrasense Tech Retreat for Internal Engineering!

This past week, the Infrasense team spent a few days in the White Mountains to share some technical knowledge, explore the snowy outdoors, and prepare for what looks to be another busy year providing clients with accurate and useful NDE testing services.

Activities ranged from an overview of our performance in 2016, a refresher on field safety practices, a deeper discussion of our proprietary software, and training with new testing equipment. But it wasn't all tech-talk; we also found time to go skiing, hike around the beautiful Echo Lake, and cook a few meals together as a team! Here are a few shots from our 2nd annual tech retreat! 

Infrared Testing: The Complementary Dual Camera System

How our high resolution video complements the abilities of Infrared.

Infrared data is collected using a FLIR thermographic camera, which measures surface temperature and can provide information regarding subsurface damage in bridge decks.  The camera is mounted to a vehicle and data can be collected at highway speeds with clear and accurate results.  After surveying each lane, the data is stitched together to create a comprehensive plan-view thermography image.

   Figure 1. IR stitch of two inner spans of a two-lane bridge with clear delamination/debonding

Figure 1. IR stitch of two inner spans of a two-lane bridge with clear delamination/debonding

The areas that appear white in Figure 1 are hot spots resulting from debonding or delamination.  When an overlay debonds or a delamination exists at the rebar-level, the resulting air void acts as a thermal barrier, producing relatively higher temperature (white blotchy areas) in the IR image.  We delineate these areas to provide both subsurface defect quantities and maps to our clients. High resolution video is also collected with the infrared data, and used to filter out surface features that produce thermal anomalies but are unrelated to subsurface conditions.   Similar to the infrared, the video data can be stitched together to create a plan-view image for a bridge deck. This image can be used to identify, quantify, and map areas of patching, spalling, and cracking.

   Figure 2.  Video proof that thermal anomaly in IR image is surface obstruction

Figure 2.  Video proof that thermal anomaly in IR image is surface obstruction

Figure 2 shows an area of thermal activity in front of the vehicle that was found to match the shape and location of surface staining in the high resolution video.  As a result, this area was delineated and categorized as a "thermal obstruction" instead of a delamination.  Obstructions can include discoloration, oil stains, rust deposits, debris, shadows, etc.

 

   Figure 3.  Video proof that thermal anomaly in IR image is due to subsurface deficiency

Figure 3.  Video proof that thermal anomaly in IR image is due to subsurface deficiency

Figure 3 shows a few areas of thermal activity, similar to what we see in Figure 2.  Playback of the video in this location shows no surface obstructions, meaning that these ‘hot spots’ are due to a subsurface thermal barrier.  These were delineated and categorized as delaminated areas.  With the aid of a visual to go with the IR data, we are able to confidently distinguished areas of subsurface distress.

State of the Practice & Future of GPR & NDT for Pavement & Deck Surveys

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On Thursday, December 1, 2016, Ken Maser, Ph.D., PE, will give a presentation on the state of the practice and the future of GPR and other forms of NDT for both pavement and bridge deck applications. The presentation will be in webinar format, via the Transportation Learning Network

The 1.5-hour webinar will cover the various applications of ground penetrating radar (GPR) and other nondestructive testing (NDT) applications around the United States. Also to be covered is a recent application of Traffic Speed Deflectometer (TSD) in Idaho, as well as the use of Infrared Thermography for bridge deck surveys. The presentation will also give insights into the implementation stage of SHRP2 involving 3D radar applications. 

Ken founded Infrasense in 1987, and is an internationally recognized authority in the field of nondestructive evaluation and subsurface condition investigations. Ken has served as a consultant to the Strategic Highway Research Program (SHRP), and has managed numerous network-level pavement and bridge deck evaluations throughout his career. 

Highway and bridge designers, project programmers, materials and research staff, and consultants in the transportation field should all tune in! The deadline to register is Monday, November 28, 2016. For more information, visit www.translearning.org