SWUTC Research Project Description
Use of Infrared Thermography to Control the Quality of Joints Construction and to Detect Reflective Cracking in Asphalt Pavements
University: Louisiana State University
Principal Investigator:
Mostafa Elseifi
Gulf Coast Research Center for Evacuation and Transportation Resiliency
(225) 578-4821
Project Monitor:
Marwa Hassan
Louisiana State University
Department of Construction Management
Funding Source: USDOT
Total Project Cost: $25,000
Project Number: 600451-00111
Date Started: 5/1/13
Estimated Completion Date: 5/31/14
Project Summary
Project Abstract:
Test methods for controlling the construction quality of flexible pavement layers and assuring the quality of new pavements have changed little over the past four decades. State department of transportation (DOT) agencies typically base their quality assessments of asphalt paving construction on localized nuclear density measurements and/or the results of testing conducted on pavement cores. For asphalt paving construction, the performance of asphalt pavements has been linked to the density achieved in the field [1-3]. Field density is intended to provide an indication of the percentage of void content in the mix. High air void may lead to premature failure due to stripping, oxidation, raveling, and ultimately cracking. Low air void may lead to rutting and shoving.
One limitation of density measurements is that the density is determined after construction is completed. In addition, measurements are localized and do not provide a complete assessment of the mat installation. Therefore, immediate corrective actions may not be taken to improve the quality of the installation. IT, also known as thermal imaging, has the potential for quality control purposes because it can be used during paving operations. This approach measures the heat radiated by the installed mat to provide a color-coded image that identifies cooler areas in blue and warmer regions in red. In recent years, the Washington State Department of Transportation successfully used infrared cameras to detect segregation due to temperature differentials in asphaltic concrete pavements [4-5]. Pavement temperature differentials are a result of cooler concentrated masses of HMA in the mat. The cooler areas end to resist compaction, creating cyclic areas of low density pavement (Figure 2). These areas will prematurely fail by raveling and/or fatigue cracking. The proposed research will investigate an innovative application of IT to assess the quality of longitudinal joints density between adjacent lanes during asphalt paving construction. This NDE technique will also be used to assess the quality of construction of HMA overlay on top of a rigid pavement as an indicator of reflective cracking potential.
Project Objectives:
The objective of this research is to investigate the potential of using Infrared Thermography (IT) as a Non-Destructive Evaluation (NDE) quality control measure of joints density during asphalt paving construction and to detect reflective cracking potential in hot-mix asphalt (HMA) overlay. Specifically, two applications will be evaluated: (1) control of longitudinal joints density during regular asphalt paving construction and its potential use for taking corrective actions during compaction; and (2) assess density of HMA overlay constructed on top of rigid pavement as an indicator of reflective cracking potential. Field experiments will be used to assess the benefits of this technology and its potential implementation as a quality control NDE tool.
Task Descriptions:
Task 1: Identify Construction Projects in Louisiana
The objective of this task is to identify a number of asphalt paving construction projects in Louisiana to collect field data using IT. Table 1 presents the experimental work plan proposed in this study. A minimum of three projects will be evaluated in the first category, which will assess the use of IT to control longitudinal joints density during regular asphalt paving construction and its potential use for taking corrective actions during compaction. The experimental plan will attempt to identify projects with three nominal maximum aggregate sizes (NMAS) and with different lift thicknesses ranging from 1.5 to 3.0 in. Similarly, a minimum of three projects will be evaluated in the second category, which will assess the use of IT to assess density of HMA overlay constructed on top of rigid pavement. Cores will be extracted or obtained from the district to measure the density and air voids of the mat using conventional methods in the laboratory.
Task 2: Conduct Field Testing
The objective of this task is to conduct the experimental plan described in Task 1. Data will be collected continuously during compaction operations with particular emphasis on the locations near the joints. However, areas away from the joints will also be scanned using IT for comparison purposes. The variation of thermal measurements during construction operations will be monitored. For HMA overlays on top of rigid pavement, the locations of the joints in the underlying concrete layer will be marked prior to asphalt paving. These areas will then be scanned using IT.
Task 3: Analyze Collected Data and Determine Feasibility of the Technology
The objective of this task is to analyze the collected field data and to determine the feasibility of the technology for the proposed application. Sensitivity of IT measurements to change in thermal variations and to weather conditions will be determined. In addition, a statistical analysis will be conducted to determine whether the surface temperature near the joints is statistically different from the surface temperature away from the joints. The change of the trends with NMAS and lift thicknesses will also be investigated.
Task 4: Develop Correlations for Assessing Construction Quality Using IT
In this task, correlations will be established between the thermal fields measured using IT and the density of the extracted cores. These correlations may be used by the Department to establish the need for corrective actions during field compaction of HMA. The change of these correlations and their validity will be determined for different NMAS and lift thicknesses.
Task 5: Preparation of the Final Report
A final report, documenting the entire research effort, will be submitted to CETR for review and comments. The final report will summarize the process and results of the experimental program. In addition, recommendations for future research to validate the proposed methodology will be developed.
Implementation of Research Outcomes:
This study assessed whether temperature differentials measured using Infrared Thermography (IRT) occur in an overlay built on top of discontinuities such as joints and cracks in an existing concrete pavement and to study the horizontal and vertical thermal profiles in the asphalt overlay using a validated Finite Element (FE) modeling approach.
Based on the results of the study, it was concluded that cracks in the existing pavement do not influence the thermal profiles in a HMA overlay. This was expected given the small width of the crack in comparison to the mat surface area, which would not cause major convection losses through the crack. However, thermal measurements on top of a joint were consistently lower than away from it, which may indicate that temperature loss may occur at the joints. While this difference may not be large enough to be identified as thermal segregation, it can influence the bulk properties of the overlay at the joints and promote early cracking.
Products developed by this research:
Journal Article Submitted for Review: Use of Infrared Thermography to Control the Quality of Joints Construction and to Detect Reflective Cracking in Asphalt Pavements, Mostafa Elseifi, submitted to the ASCE Journal of Materials in Civil Engineering, currently under review.
Curriculum Module Developed: Results from this research will be utilized in a technical elective class taught by Dr. Mostafa Elseifi at Louisiana State University.
Impacts/Benefits of Implementation:
Results of this research will help inform asphalt contractors and state agencies in highway overlay construction.
Web Links:
Final Technical Report