Radar measurements assess the integrity of concrete civil structures after fires

After a fire, it is crucial to assess concrete civil structures for damage, but conventional approaches for monitoring structural health can themselves be partially destructive. To evaluate the integrity of fire-damaged concrete materials, Singh et al. developed a non-destructive method for finding cracks and voids.

“Various other techniques have been studied to improve damage detection, especially to improve the accuracy in nondestructive techniques,” said Dharmendra Singh.

As exposure to extreme temperatures causes the quality of the concrete to deteriorate, the velocity of an ultrasonic pulse traveling through the structure is reduced. Measuring this velocity can thus locate anomalies in the material. In particular, the group’s approach relies on using millimeter wave radar to measure the transmission and reflection of the ultrasonic pulse through the concrete. They extracted the real part of the material’s permittivity from these measurements, which helps decipher where specifically the abnormality is.

“A direct relationship with the depth and damage was easily visible in this representation of measured values,” Dharmendra Singh said.

To validate their proposed method, the researchers compared concrete heated to 800 C with a control specimen, and observed changes in its physical, mechanical and microstructural properties. The results agreed well with conventional approaches.

For practical implementation of this technique, the group plans to develop a handheld, portable analyzer that can provide automated measurements, completed with a user-friendly interface for visualizing the damage.

Source: “Development of a novel approach to detect damage in concrete structures with millimeter wave radar assessment system,” by Sanjeev K. Singh, Naina Narang, and Dharmendra Singh, Review of Scientific Instruments (2021). The article can be accessed at https://doi.org/10.1063/5.0045700 .