Application Scheme-Infrared thermography to monitor the heat recovery process in the repair of asphalt pavement

Infrared thermal imaging to monitor the heat recovery process in asphalt pavement repair

For many years, due to the 100% use of recycled asphalt pavement RAP materials, a popular maintenance technology-on-site heat recovery (HIR) is used for the repair of asphalt pavement. Only 10% to 20% of the original material can be re-mixed with RAP material to complete the renovation of asphalt pavement. Therefore, HIR can reduce road maintenance costs and adversely affect the environment. Moreover, multiple road problems such as rutting, tearing and cracking can be handled simultaneously. In HIR, operations such as heating, soil loosening, regeneration, mixing, placement, and compaction are required to repair the pavement, and these operations are performed at the construction site. One of the most challenging processes is the heating process. Insufficient heating will not soften the pavement well; excessive heating will cause the asphalt binder to age seriously, affecting the repair performance of the pavement. Therefore, it is necessary to strictly monitor and control the heating quality during the HIR construction process.

At present, construction personnel use infrared temperature guns to monitor the temperature through a single-point temperature monitor (SPTM) during the HIR heating process. SPTM measurement results only represent a certain point temperature, not the entire surface temperature. More importantly, in the previous literature and existing construction codes, there are no indicators for evaluating the quality of HIR heating.

The picture shows the three stages of the heating system monitored by the infrared camera

Therefore, it is necessary to propose a more reliable method for heating temperature monitoring and heating quality evaluation in HIR. The infrared camera can receive the infrared radiation emitted by the detector from the object, and then display the thermal image of the temperature distribution through the signal processing system. The advantage of this technology is that it can measure the entire temperature data of the road surface at the same time, rather than the limited observation point to monitor the heating process of HIR.

The picture shows the RGB road map and infrared thermal image

In this study, infrared thermal imaging cameras were used to monitor the on-site heating temperature of the three heating systems, and three indicators were established to evaluate the temperature uniformity and heating effect. Higher road temperature and poorer temperature uniformity are more likely to cause overheating. Especially as the road temperature increases during the heating process, the requirements for temperature uniformity will become more stringent. Studies have shown that infrared thermal imaging technology can achieve detailed monitoring of pavement temperature during the multi-level heating process of HIR. The combination of digital image processing and neural network can extract and correct deformation temperature maps to restore pavement temperature data.

Reference materials:

Dongdong Han, Yongli Zhao, Yuanyuan Pan, et al. Heating process monitoring and evaluation of hot in-place recycling of asphalt pavement using infrared thermal imaging [J]. Automation in Construction, 111:103055, 2020.