Thermal mapping has been implemented since the late eighties to establish the susceptibility of road networks to ice occurrence with measurements from a radiometer and some atmospheric parameters. They are usually done before dawn during wintertime when the road energy is dissipated. The objective of this study was to establish if an infrared camera could improve the determination of ice road susceptibility, to build a new winter risk index, to improve the measurements rate, and to analyze its consistency with seasons and infrastructures environment. Data analysis obtained from the conventional approved radiometer sensing technique and the infrared camera has shown great similarities. A comparison was made with promising perspectives. The measurement rate to analyse a given road network could be increased by a factor two.

The mobility during winter season in France mainly relies on the use of de-icers, with an amount ranging from two hundreds thousands tons up to two millions tons for the roads only. Besides the economic impact, there are many concerns on their environmental and infrastructure, both on roads and on airports. In such context and in the framework of the R5G (5th Generation Road) project driven by IFSTTAR, investigations were carried out on the way to modify the infrastructure to maintain pavement surface at a temperature above water freezing point. Two distinct approaches, that can could be combined, were selected. The first one consisted in having a heated fluid circulating in a porous layer within an asphalt concrete pavement sample. The second one specifically relied on the use of paraffin phase change materials (PCM) in cement concrete pavement ones. Experiments on enhanced pavement samples were conducted in a climatic chamber to simulate winter conditions for several continuous days, including wind and precipitations, and monitored by infrared thermography. Studies concerning the first approach consisted in identifying the temperature range of the fluid to maintain asphalt concrete surface freezing-free. Both experimental and numerical approaches were conducted showing the importance of the role of the hydraulic conductivity of the porous layer. The analysis of infrared images indicated a surface temperature above freezing excepted in one situation, for which cold air convection and precipitations were combined at pavement surface. A temperature gradient along the surface was also observed. A good agreement was found between numerical and experimental results. To moderate the effect of precipitation, several PCM insertions were chosen and inserted at different depths, with various volumes and packaging (liquid, or powder of encapsulated liquid paraffin). At this stage of the study, rather mixed results were obtained. Delay in the surface ice formation was not conclusive, probably due to deeper location and an unsufficient amount of PCM used. Further investigation to carry out by coupling numerical and experimental approaches would help in refining the use of PCM for this application. The proposed paper will address the presentation of infrared monitoring developed during these studies.