Evaluation of Impact of Hot-Mix Asphalt Density Differentials on Thermal Streak Phenomenon by Passive Infrared Thermography

Abstract

The impact of hot-mix asphalt (HMA) density differentials on thermal streaks and their temporal evolution were examined by means of infrared thermography under laboratory conditions. A series of experimental tests was performed using specimens containing three asphalt blocks, one of which had an arbitrarily lower density and was positioned between the other two blocks with higher densities. The specimens were uniformly heated to a temperature similar to that found in real on-site situations during HMA laydown and left to cool at ambient temperature, simulating a thermal streak caused by density differentials. Surface cooling at ambient temperature was recorded using a thermographic camera. Results demonstrated that HMA density variations of 6.5% or higher produce surface temperature differentials of 4°C or more after 3 min of cooling, and can be straightforwardly detected by infrared thermography. Thermal modeling confirmed the experimental trends and constitutes a valuable tool for future investigation under different conditions.