Thermography is defined as a diagnostic technique in which an infrared camera is used to measure temperature variation on the surface of a body. The infrared camera actually detects the amount of infrared radiation that reaches the lens of the camera. There are several factors that affect this reading. One major factor is the emissivity of the object. Emissivity is the ratio between the amounts of radiation emitted by a body compared to a black body at that same temperature. Basically this is a calibration factor that ensures the camera is able to compute the correct temperature read-out. Other variables that affect the temperature read-out are ambient temperature, relative humidity and the distance from the object to the camera.
The infrared camera can reveal the inconsistencies in the mat temperature. As a result of temperature variations, consistent compaction results can be affected. In the example below, the temperatures were not significantly low as to adversely affect the compaction. The contractor met the compaction specifications, as measured by a nuclear densometer. The below photos were captured during the paving phase of State Route 123 (SR 123) road reconstruction project. The SR 123 project was located in Mt. Rainier National Park between mileposts seven and eleven. |
