Aidin J. Golrokh

Many studies were conducted to find possible strategies for reducing the urban heat island (UHI) effect during the hot summer months. One of the largest contributors to UHI is the role that paved surfaces play in the warming of urban areas. Solar-reflective cool pavements stay cooler in the sun than traditional pavements. Pavement reflectance can be enhanced by using a reflective surface coating. The use of heat-reflective coatings to combat the effects of pavements on UHI was pre-viously studied but no consistent conclusions were drawn. To find a conclusive solution, this work focuses on the abilities of heat-reflective pavement coatings to reduce UHI in varying weather conditions. Within this context, both concrete and asphalt samples were subject to a series of per-formance tests when applied to a heat-reflective coating, under the influence of normal, windy, and humid conditions. During these tests, the samples were heated with a halogen lamp and the surface temperature profile was measured using an infrared thermal camera. The air temperature was recorded with a thermometer, and the body temperature at multiple depths of the samples was measured using thermocouples. The results from these tests show that the effectiveness of the heat-reflective coating varies under different weather conditions. For instance, the coated samples were about 1 °C cooler for concrete and nearly 5 °C cooler for asphalt, on average. However, this temperature difference was reduced significantly under windy conditions. As such, the findings from this work conclude that the heat-reflective coatings can effectively cool down the pavement by increasing the surface albedo, and thus might be a viable solution to mitigate UHI impacts in the city/urban areas.

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.

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.

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.