Automated Whole Life Road Repair and Thin Surfacing | INNOVATE UK PROJECT 10053184
This project will provide confidence for the industrial partners to move forward with the production of AI-enabled robotic repair heater products that autonomously collect and apply multiple sensor data in heating. Our adoption of renewable electrical power eliminates the current reliance on hazardous LPG gas and polluting diesel-powered generation. Our predicted marketing within the plant-hire industry will disrupt the road repair market.
While alternative cold repair materials have been investigated, hot-placed asphalt remains the preferred option for road-wearing courses. However, current equipment and methods used in repairing, e.g., potholes, are inherently unreliable and frequently characterized by early failure. There is a similar need to ensure long life and cost savings with thin asphalt overlays that promise to drastically reduce the carbon footprint of road pavement upkeep.
The state-of-the-art in heated asphalt repair uses an LPG gas-powered, manually operated heater applied to heat the placed asphalt surface (typically to 130-160°C). Control feedback relies on near-surface air temperature sensing with a safety cut-out to avoid overheating and the dangerous ignition of asphalt’s bituminous content. Heaters are sometimes used in ad hoc clearing of loose material within the host surface.
Eight years of investigation by the project team into repair with accelerated life testing of pothole-type defects prove that current equipment and methods are unreliable because they do not operate according to the fundamental principles of thermal energy transfer in solids. Without this, it is not possible to predictably fuse newly applied asphalt to the existing concrete or asphalt base and thus deliver repair life comparable to the residual life of the surrounding road. For predictable fusion, temperatures in the host-fill boundary region must exceed the so-called cessation temperature of asphalt (85°C) during the compaction process that follows the placement of the introduced asphalt. Using our in-house developed numerical models, founded on heat transfer science, we have discovered that combinations of climatic conditions, internal heat dissipation, and imperfect heat transfer across the host-fill boundary can result in temperatures substantially lower (e.g., 50°C) than the cessation temperature in the boundary region, even when asphalt is introduced at a high temperature (e.g., 160°C). Our in-house developed, unique, 3D-printed, multi-thermocouple sensor, which simultaneously measures temperatures above and below this boundary, has enabled us to verify this. Currently operated quality control methods based on completed surface temperature only are thus proven misleading.