A camera method reads 3D-printed concrete as it hardens

Eight feet of wall, and the bottom layer starts to crack. Nobody on site can see it. Engineers at Rowan University say they now have a way to watch that happening, while the wall is still being printed and cured. Their method measures how 3D-printed concrete deforms as it is built, including how lower layers respond each time new material is laid on top.

The starting point is an old tool. Digital image correlation, or DIC, tracks deformation by comparing camera images against a reference image taken before the load or movement began. The difficulty with printed concrete is that there is no reference: the structure is still being built, and the picture of its starting state does not exist. Islam Mantawy, assistant professor in civil and environmental engineering at Rowan, put the stakes plainly. A structure that fails mid-build forces teams to start over, and a method meant to be faster and cheaper becomes slower and less efficient.

The team's answer was to reverse the direction of the analysis. Behrad Koohbor, associate professor of mechanical engineering, described it as writing the history of the process by starting from the end and going back. The researchers worked backward from images of the finished structure through thousands of images captured during printing and curing. They found that the concrete's own surface roughness acted as the tracking pattern, so no markers had to be added to the material. A mathematical approach then validated the method.

For builders, the practical gain is early warning. The researchers note that temperature, humidity and chemical composition all shape how a printed structure cures, and that tracking them could help engineers catch a problem before it spreads to the rest of the wall. The same logic, they argue, could serve other additive manufacturing processes, where quality control is limited because no finished part exists when production starts. Mantawy linked the work to a longer goal: without knowing what is happening inside the structure, self-operating 3D printing will not be possible. The source does not say how accurate the measurements are, at what scale the method has been tested, or when it could move from the research team's work to construction sites.