A major factor in the construction of a building is determining when the concrete of each floor is strong enough to add loads. This typically involves testing the concrete mix designs before they are implemented in a project, and, once approved, any changes to the mix must undergo additional offsite testing before they can be approved and used. Changes can become necessary due to unexpected weather or other schedule disruptions. All of this takes valuable time — as much as a month — before the concrete is even poured at the job site.

Purdue engineers have designed technology that eliminates the need for time-consuming offsite testing and safely speeds up the construction timeline. The team developed sensors that allow construction contractors to verify the maturity of the concrete onsite.

“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 Luna Lu, professor of civil engineering at Purdue. “That starts with industry collaborations to evaluate how well the sensors work.”

The team is working with F.A. Wilhelm Construction Co. Inc. to test the sensors and compare the results with traditional commercial sensors. The test is being conducted on Purdue’s five-story Engineering and Polytechnic Gateway Complex, currently under construction. Twelve sensors have been installed in the third floor of the complex.

The team is also testing the sensors on Indiana highways to determine when concrete is ready to withstand heavy truck traffic.

“Our sensors could help make better data-driven decisions to determine the construction schedule and improve the quality of concrete construction,” said Lu. The sensors developed in her lab eliminate the need to develop a maturity curve in advance. Instead, they measure the strength of the concrete from the floor deck in real time.

The sensors use electricity to send an acoustic wave through the concrete. The concrete’s response to the wave speeds indicates its strength and stiffness. This provides information on the concrete’s microstructure as well as how strong it is.

“These new sensors are more of a ‘plug and play.’ We could make judgment calls on the fly,” said Ryan Decker, Wilhelm’s corporate quality assurance manager.

The team is currently working on a system for contractors to remotely receive information from the sensors.