Sustainable and performing technologies for safe and innovative road maintenance

Maintenance is a very important aspect of road user safety. It becomes crucial when it has to be carried out in winter, as road damage/potholes develop exponentially due to the effects of rain, freezing/thawing and heavy traffic. However, especially for high-traffic roads, maintenance operations are not as easy and safe for workers, as it is often not possible to close the road section to traffic. An innovative, compact and autonomous vehicle capable of repairing potholes can be used to solve this problem. This system is equipped with a 3D printer capable of extruding an asphalt mixture directly onto the pothole. The rehabilitation is carried out in two stages. In the first, the robot maps the location, size and depth of the pothole. Then, after processing the data, it autonomously calculates the amount of material to be loaded into its material tank and unloads it into the pothole. Finally, the vehicle traffic will take care of the compaction of the material. In this study, three different bituminous mixtures commonly used for pothole repair were investigated. The first was a cold asphalt mixture composed of natural aggregates, bitumen emulsion, and cement. The second was a hot mix asphalt applied at ambient temperature, consisting of basalt aggregates, reclaimed asphalt pavement (RAP), bituminous membranes, cement, and a fluxing oil. The third was a cold asphalt mixture composed by 100% RAP, a multifunctional additive, cement, and water. Each mixture was evaluated in terms of Indirect Tensile Strength (ITS), Marshall Stability, and Particle Loss (PL) after 28 days of curing. Based on the experimental results, the third mixture demonstrated the best overall mechanical performance and was the only one to meet the minimum requirements set by the Lombardy region. Consequently, it was selected for further investigation. A second phase of testing was carried out to optimize the contents of rejuvenating additive and water, aiming to further enhance its performance and compliance with technical specifications. The implementation of these mixtures through the automated robotic system has proven to be an excellent way to improve the safety of road maintenance operators, ensuring excellent road infrastructure quality, while using high-performance and sustainable materials in line with the requirements of the European Green Deal.