December 6, 2023

In partnership with private industry, the University of Cambridge has taken 3D printing one step further by not only fabricating concrete infrastructure units in an hour, but integrating sensors to allow it to monitor itself and one day repair itself.

If there’s one topic least likely to spark a lively discussion at dinner, it’s the bits and pieces of civil engineering that people see while driving the national road network. These are so often taken for granted that they might be invisible unless they are something as spectacular as a drawbridge, or something nasty like a road being resurfaced.

However mundane these may seem, they are the product of some very complex and serious engineering and have a very real and important function that many people don’t realize until the road ahead washes away or the ramp collapses.

One of these is the so-called head wall, which is a retaining structure with holes placed at the mouth of a drain or culvert. Its purpose is to anchor a culvert or similar and prevent the fill around it from being washed away by running water. In addition, it can provide structural support for attached bridges and roads and control water flow.

It’s a very old piece of civil engineering, but Cambrdige has given a new twist to the one installed on the Cornish A30, using a robotic 3D printer arm to build it on site, laying down layers of fast-setting concrete that harden in just an hour. Again, not very new. The novelty is that while the end walls are being printed, the LiDAR unit precisely scans the structure, creating a digital virtual twin that can be compared to the real thing.

Additionally, wireless sensors were placed in wet concrete to transmit data on temperature, strain, pressure, humidity, resistivity, and electrochemical potential.

Temperature is of particular interest because rapid-setting concrete generates a lot of heat, which can damage the end walls as it hardens and cures. This is important because another innovation of the new structure is that it does not use a traditional steel skeleton. Instead, it relies on its own geometry for strength, which isn’t easy with something with hollow, curved interior walls.

The experiment, led by Professor Abir Al-Tabbaa from the University of Cambridge’s Department of Engineering, aims to use sensors and digital modeling to assess the stability of 3D printed structures, making them more attractive to industry. In addition to creating something that is cheaper and faster to build than conventional structures, the goal is to test the reliability, robustness, accuracy and longevity of the sensors themselves and, perhaps one day, employ a self-healing concrete that the team is developing.

“This project will serve as a living laboratory, generating valuable data over its lifetime,” Taba said. “Sensor data and ‘digital twins’ will help infrastructure professionals better understand how to use and customize 3D printing technology to print larger, more complex cement-based materials for strategic road networks.”

The video below discusses the new smart 3D printed concrete structures.

end wall

source: University of Cambridge