A growing number of highways in the United States are set to pilot a Purdue University invention that could save taxpayers millions of dollars and dramatically reduce delays in traffic.
The invention, a sensor that allows concrete to “talk,” reduces construction time and the number of times concrete pavers need repairs while improving road sustainability and reducing carbon emissions.
The sensor is integrated directly into the formwork, sending engineers more accurate and consistent data about concrete strength and the need for repair than is possible with the tools and methods currently in use.
“For example, we don’t know when concrete will reach the proper strength needed to accommodate traffic loads immediately after construction,” said Lona Low, a Riley Professor and acting chair of Purdue’s Lyles School of Civil Engineering, who has been leading sensor development since 2017. “Concrete may go through past failures.” Premature, which leads to frequent repair.
According to data from the Federal Highway Administration, concrete pavement makes up less than 2% of US roads but nearly 20% of the US interstate system. Low’s research focused on improving the conditions of concrete pavement first because it is the most difficult road material to repair. Interstate concrete pavement must reliably support a significant proportion of the nation’s traffic.
More than half of US states with concrete interstate pavement signed up to participate in a pooled funding study for the Federal Highway Administration to implement the sensors. The participating states are Indiana, Missouri, North Dakota, Kansas, California, Texas, Tennessee, Colorado, and Utah.
Other states are expected to join as the study begins in the coming months. Two states — Indiana and Texas — have already begun experimenting with the sensors on highway paving projects.
The technology is also on its way to hitting the market later this year as the REBEL Concrete Strength Sensing System, a WaveLogix product. Le founded WaveLogix in 2021 to manufacture the technology on a larger scale. The company licenses the technology from Purdue Research’s Office of Technology Commercialization, which has filed for patent protection on the intellectual property.
Fast Company magazine named the invention one of the next big things in tech for 2022, which recognizes projects that are already having an impact on a real-world problem while also showing promise for making an even bigger impact in the years to come. The American Society of Civil Engineers’ 2021 Report Card for American Infrastructure also named the technology as one of its “Game Changers” for the year. Other organizations, such as the American Highway Association and state transportation officials, have followed the technology’s developments since it was first introduced in 2019.
Replacing outdated industry standards to make roads last longer
Purdue’s invention is gradually rising as a better alternative to the tests that have been the industry standard since the early 20th century.
Lu and her lab began developing the technology in 2017, when the Indiana Department of Transportation asked for help eliminating premature failure of a newly repaired concrete sidewalk by pinpointing more precisely when the sidewalk was ready to open to traffic.
After including an early prototype of the sensor in sections of various highways in Indiana, INDOT added the sensor technology to its Indiana Test Roads catalog. This catalog lists tests that contractors and construction workers use to ensure road pavement quality.
Methods used by the industry for more than a century require large samples of concrete to be tested in a laboratory or on-site facility. Using this data, engineers estimate the level of strength a given concrete mix will reach after it has been poured and left to mature at a construction site. Although these tests are well understood by the industry, discrepancies between laboratory and outdoor conditions can lead to inaccurate estimates of concrete strength due to different cement compositions and ambient temperatures.
With the technology Lu and her team invented, engineers no longer need to rely on concrete samples to estimate when fresh concrete has matured enough. Instead, they can observe fresh concrete directly and accurately measure several of its properties at once.
The sensor communicates with engineers via a smartphone app exactly when the pavement is strong enough to handle heavy traffic. The stronger the pavement is before vehicles use it, the less repair is needed. The ability to receive real-time information about concrete strength levels also allows roads to be opened to traffic on time or sooner after a new pour.
Construction workers can install the sensors by simply throwing them onto the floor of the concrete formwork and covering them with concrete. Next, they connect the sensor cable to a reusable portable device that automatically starts recording data. Using the app, workers can receive information on real-time changes in concrete strength for as long as strength data is required.
Reduce carbon emissions by reducing traffic and cement
By reducing road repairs and construction schedules, this technology can reduce the carbon dioxide that vehicles may emit while waiting in traffic to get around a construction site.
WaveLogix, a startup, is developing a way to reduce carbon emissions by lowering the amount of cement needed in concrete mixes. Cement manufacturing is responsible for 8% of the global carbon footprint. WaveLogix has advanced a solution that uses artificial intelligence to optimize the design of concrete mixes based on data that sensors will collect from highways across the country.
Building codes require a higher cement content in concrete mixes to ensure that the sample tested concrete meets the required strength thresholds. Excess cement can lead to premature cracks in the pavement. Based on these code requirements and data from the World Cement and Concrete Association, Low estimates that overdesigning concrete mix causes more than 1 billion tons of carbon emissions annually.
“The biggest problem with concrete admixtures is that we use more cement to increase the strength of the concrete. It won’t help open the road for traffic sooner,” Lu said.
These codes are based on how concrete mixes were made in the early 1900s, which was before equipment that could grind cement into a fine powder was developed in the 1950s. Because concrete mixes use this fine powder today, they must have different water-cement ratios than they did a hundred years ago. The codes also do not take into account how weather in different states affects the concrete mix. Pouring concrete in the middle of an Indiana winter, for example, requires different concrete mixes to reach the proper level of strength than if the concrete was poured during a California winter.
Lu believes that this new method using artificial intelligence can reduce by 20% to 25% the amount of cement used in concrete mixes – and at the same time make pavement more durable and less expensive.
“I feel a strong sense of responsibility to make an impact on our infrastructure by developing new types of technology. In civil engineering, if we don’t make an impact on the world, there is no world to worry about,” Lu said.