Full-Scale Study of Infrared Thermography for Assessing Surface and Subsurface Defects in Pavements and Other Civil Infrastructure

Infrared thermography (IRT) is an effective non-destructive testing method in the field of concrete and asphalt pavements inspection. IRT is used to have an initial evaluation of the surface and near surface of pavements in a very time effective manner compared to other types of nondestructive testing (NDT) methods. Different aspects of IRT and its use to assess surface and subsurface defects in different types of pavements are being studied and evaluated in our research group. The effect of the depth of delamination inside concrete pavement on IRT technique is being studied. It is suggested by our group that there is a correlation between the surface crack profile on the asphalt pavements and its temperature, which will help us to evaluate pavement performance condition. Finally, a full laboratory study is being conducted to experimentally quantify the effects of weather conditions and surface coating on the ability of IRT to assess surface cracks on both asphalt and concrete pavements

Application of Infrared Thermography in Pavement Inspection

Infrared thermography (IRT) is an effective non-destructive testing method in the field of concrete and asphalt pavements monitoring. IRT is used to have an initial evaluation of the surface and near surface of pavements in a very time effective manner. The effect of the depth of delamination inside concrete pavement on infrared thermography technique is being studied. It is also suggested by our group that there is a correlation between the surface crack profile on the asphalt pavements and its temperature. Finally, a full laboratory study is being conducted to experimentally quantify the effects of weather conditions on IRT

Concrete Pavement Service Condition Assessment Using Infrared Thermography

Infrared thermography (IRT), an effective nondestructive testing method, is used to obtain an initial evaluation of the concrete pavement surface and near surface in a time effective manner. In this paper, the effect of the depth of delamination inside concrete pavement on infrared thermography technique is studied for bridge decks inspection. To be able to mimic the delamination in subsurface, two Styrofoam cubes have been inserted in different depth near the surface of the concrete cylinder. After heating up the specimen, thermal images were taken from the surface using an infrared thermal camera to evaluate the effect of subsurface defects on detection sensitivity and accuracy.We also investigated the precision to which the shape and the size of the subsurface anomalies can be perceived using an uncooled thermal camera. To achieve this goal,we used image processing technique to accurately compute the size of delamination in order to compare it with the actual size. In addition, distance/thermal graph is used to detect the presence of the defect underneath the concrete surface. Furthermore, thermal transfer modeling was adopted in this paper to assist the setup of this experiment and the results are compared with laboratory findings

3D Crack Profiling Using Real-Time Thermography

The objective of this research is to develop an integrated new system that combines infrared imaging, high resolution visible light imaging, real-time image processing, and data-rich analytics for automated inspection of the surface of the asphalt pavements. The developed system features collecting frames from thermal and visual images and aligning them together for further data processing. We developed an algorithm that can integrate the characteristics captured by both thermal and visual images to provide a quantitative identification of the location of surface cracks and their severity. This work can provide fast and easy decision support to improve pavement preservation practices

An Experimental Study of the Effects of Climate Conditions on Thermography and Pavement Assessment

This paper presents a testing set-up that helps to observe and quantify the effects of different weather conditions on the thermal profiles related to the surface crack on concrete infrastructures. The temperature data for this research are generated using infrared thermography (IRT). IRT is prominently used to monitor surface and close-to-surface defects on pavements. However, the method is more prone to adverse effects of weather conditions compared to other types of nondestructive tests. This is because IRT relies on the temperature profile of the surface of the target. In this research, a full laboratory study is conducted to experimentally quantify the effects of weather conditions and surface coating on the ability of IRT to assess surface cracks on concrete pavements. The goal is to determine the significance of these effects on IRT under each weather condition. IRT technology can be affected by critical environmental conditions, such as sunlight, ambient temperature variation, wind speed and humidity. Many research studies have mentioned the importance of the effect of weather conditions, but no research is dedicated to experimentally quantifying the effect. Around 90 different tests have been conducted from which 1050 unique data points have been extracted. Eventually, around 1,260,000 temperature data have been gathered which gives a huge dataset will give us the opportunity to do several statistical analyses. It is found that wind has a higher effect on the temperature of the crack on concrete pavements compared to humidity in the air. Even though both wind and humidity can affect the temperature of the crack, the different wind speeds and humidity levels have roughly the same amount of effect on the temperature

Chemomechanical Modeling of Sulfate Attack–Induced Damage Process in Cement-Stabilized Pavements

Cement-stabilized pavement layers are subject to sulfate attack (SA) in sulfate-abundant regions due to internal expansion– induced damage throughout its expected service life. SA is a coupled physical-chemical-mechanical damage process for cementitious materials involving complicated chemical reactions between sulfate and components of cement composite. SA contains intricate interactions among porous media, moisture transport, and heat transfer. Engineering mechanics has been used to explain the failure process of the internal expansion caused by this coupled physical-chemical ingress phenomenon. Existing studies have considered only heat transfer or moisture content–dependent modeling. The literature lacks a comprehensive model that considers coupled interaction of temperature and humidity upon sulfate ingression. Thus, a chemomechanical (CM) model has been developed for capturing the true failure process of cement-stabilized pavement subgrades under SA. In this paper, a set of governing equations are developed, and a unique expression for a moisture-dependent and heat-dependent sulfate diffusion coefficient is proposed. Consequently, the equations are solved using the finite-element method. The results conform well with experimental results. The model has been validated to be accurate enough compared with previously implemented models. It is capable of evaluating and predicting SA-induced expansive failure in unsaturated cement-stabilized pavements. Two different models were combined to estimate the mechanical behavior of cement-stabilized subgrades subject to SA. Finally, the Drucker-Prager (DP) failure criterion was used for determining the damage zone

Real-Time Thermal Imaging-Based System for Asphalt Pavement Surface Distress Inspection and 3D Crack Profiling

Infrared thermography is a cost-effective nonintrusive testing approach to assess surface and near-surface distresses, such as asphalt pavement surface cracks. However, the raw data collected by thermal cameras cannot be directly used for pavement surface distress inspection. Thus, advanced thermal image processing methods are desirable for extracting indicators of hidden flaws. The objective of this research was to develop an integrated system that combines infrared imaging, high-resolution visual imaging, real-time image processing, and data-rich analytics for automated inspection to support decision making for pavement preservative maintenance. This work developed a code that can integrate the characteristics captured by both thermal and visual images to provide a quantitative identification of the surface cracks and their severity. Field-test data were collected and a statistical analysis was conducted to correlate temperature gradient to the surface crack profile of asphalt pavement. It was found that the surface temperature distribution pattern has a direct correlation with pavement crack profile, and can be used as an indicator of crack depth. The proposed real-time thermal imaging-based system was found to be feasible for field inspection, and the three-dimensional (3D) crack profiling method can help produce fairly accurate measurements to enable fast and easy decision support for pavement preservation practices

Concrete Pavement Service Condition Assessment Using Infrared Thermography

Infrared thermography (IRT), an effective nondestructive testing method, is used to obtain an initial evaluation of the concrete pavement surface and near surface in a time effective manner. In this paper, the effect of the depth of delamination inside concrete pavement on infrared thermography technique is studied for bridge decks inspection. To be able to mimic the delamination in subsurface, two Styrofoam cubes have been inserted in different depth near the surface of the concrete cylinder. After heating up the specimen, thermal images were taken from the surface using an infrared thermal camera to evaluate the effect of subsurface defects on detection sensitivity and accuracy. We also investigated the precision to which the shape and the size of the subsurface anomalies can be perceived using an uncooled thermal camera. To achieve this goal, we used image processing technique to accurately compute the size of delamination in order to compare it with the actual size. In addition, distance/thermal graph is used to detect the presence of the defect underneath the concrete surface. Furthermore, thermal transfer modeling was adopted in this paper to assist the setup of this experiment and the results are compared with laboratory findings

Use of Heat-reflective Coatings for Reducing the Contribution of Pavement in Urban Heat Index

Many studies have been conducted to find possible strategies for reducing the Urban Heat Island (UHI) effect during hot summer months. One of the largest contributors to UHI is the role paved surfaces play in the warming of urban areas. The use of heat-reflective coatings to combat the effects of pavement have been previously studied, with mixed conclusions. While studies show that heat-reflective coatings may have many useful applications, this study is focused on their ability to reduce UHI. To elaborate this, a concrete sample is put through tests in which it is heated with a halogen lamp and the surface temperature is measured using an infrared thermal camera. The air temperature and body temperatures at varying depths are also recorded using a thermometer and thermocouple respectively. Analyzing the limited results that have been collected thus far found that the concrete was cooler when coated as compared to the concrete samples without coating. This conclusion shows that heat-reflective coatings are capable of reducing the surface temperature of concrete and may have the potential to lessen UHI effects in cities

Materials Characterization and Testing of Heat-Reflective Coatings to Mitigate the Urban Heat Island

The Urban Heat Island (UHI) effect—urban areas higher in temperature than rural counterparts—is exacerbated by pavement surfaces. Heat-Reflective Coatings (HRC) are being developed to cool pavements for UHI mitigation. Six HRCs were tested via engineering performance tests, spectroscopy, and microscopy to determine changes in surface temperature and to understand optimal cooling mechanisms of each coating based on microstructure-property-performance architecture. Integrated multimodal characterization approaches were used to: 1. Determine the micro/nano scale heat reflection mechanisms that in each coating material; 2. Compare the heat reflection performance of each coating and rank them by cost effectiveness; 3. Inspire the design and optimization of new cool pavement with specifications and recommendations. During engineering performance tests, coated concrete samples underwent heating and cooling cycles in which the surface, atmospheric, and subsurface temperatures were recorded using an infrared thermal camera, a thermometer and thermocouples, respectively. Results from performance testing clearly demonstrated an overall decrease in surface temperature for coated samples compared to uncoated concrete. Ultraviolet-Near-Infrared and Fourier Transform Infrared spectrometers were used to quantify solar and thermal reflectance and HRCs were found to have significantly higher reflectance in the visible and near-infrared range compared to uncoated concrete. Scanning Electron Microscopy imaging of HRCs revealed the presence of silicon dioxide and titanium dioxide nanoparticles of varying size and morphology. Results of engineering performance testing and multimodal characterization indicate the potential of using HRCs to mitigate the UHI effect by cooling pavement surfaces