Construction Technology

Purdue Concrete Sensors Could Speed Construction Onsite

• By Dian Schaffhauser
• 02/11/21

Engineering researchers at Purdue University have come up with sensors that can determine concrete strength onsite in real-time, and they're testing it right on campus. The hope is that the technology will help builders speed up their construction timelines safely.

According to a campus article, concrete mix designs are tested offsite for "compressive strength" before their use in a construction project. Once the testing is done and the mixes vetted for use, they can't be changed without additional testing. The new sensors would eliminate the need for offsite testing by enabling contractors to verify the concrete's maturity right on the jobsite.

The researchers are working with F.A. Wilhelm Construction Co. to test and compare the technology with traditional commercial sensors installed into a floor of what will be Purdue's five-story Engineering and Polytechnic Gateway Complex. The construction site is managed by Shiel Sexton Co. Inc. and the building is expected to be completed in fall 2022.

"Our sensors could help make better data-driven decisions to determine the construction schedule and improve the quality of concrete construction," said civil engineering Professor Luna Lu.

Lu and her research team also are testing the sensors in highways across Indiana as part of an effort to better determine when concrete is ready to take on heavy truck traffic.

"We're trying to work with contractors to find out how much saving we can do for them in terms of time, cost and the number of people needed at a site, which reduces risk and improves construction safety," said Lu. "That starts with industry collaborations to evaluate how well the sensors work."

Sensors aren't a new addition in testing concrete strength and maturity. General contractors have used them over the last decade. But before the concrete is poured, the mixes have to be tested for strength based on varying temperatures and the results graphed. That graph is used to match up temperature measurements from sensors in the field. Strength values on the graph, called a "maturity curve," help site managers estimate when the concrete is strong enough to continue construction.

If unexpected weather or some other impact calls for a change in the mix, the testing process has to start over again.

The sensors developed by Lu's lab would measure concrete strength directly from the floor deck in real time, eliminating the need for generating a maturity curve beforehand.

Lu's sensors remain in the concrete and generate a measurement of strength by using electricity to send an acoustic wave through the material. How concrete responds to particular wave speeds indicates its strength and stiffness at the microstructure level.

Plus, they're easier to use, said Ryan Decker, Wilhelm's corporate quality assurance manager. "These new sensors are more of a ‘plug and play,' he noted. "We could make judgment calls on the fly."

Twelve of Lu's sensors have been installed into various sections of the Gateway Complex's third floor so that the teams can best understand how well they work compared with commercial sensors in use on the site.

Now, Lu's lab is developing a system to let contractors receive the concrete's strength information remotely.

The sensor technology has a patent filed through the Purdue Research foundation Office of Technology Commercialization.

A video about the sensor testing is available on YouTube.