Monitoring the Internal Conditions of Road Structures by Smart Sensing and In Situ Monitoring Technology: A Review

Internal-condition sensing for road structures is crucial for road service safety, performance assessments, and maintenance. In recent years, new technologies for monitoring structural conditions of roads have been updated, significantly improving road-sensing capabilities. Most of these techniques use a new generation of sensors and monitoring systems by means of buried sensors in roads to obtain the accurate mechanical status of road-internal structures. This paper presents an exhaustive and systematic literature review of in situ sensing technology for the internal-structure conditions of pavements in the past 20 years. The principles, advantages, and disadvantages of existing monitoring sensors, such as fiber-optic grating sensors and resistive strain gauges, and their applicability in pavement monitoring are reviewed. Meanwhile, sensing technology based on conductive sensitive materials (CSMs) are shown to have broad application prospects, and the details of conductive polymer compositions, preparation processes, and sensing performance factors are discussed. Lastly, further opportunities and challenges for using polymer CSMs for in situ road monitoring are highlighted.