Concrete results

Weina Meng, an assistant professor of civil engineering at Stevens Institute of Technology, is developing a new, low-cost ultra-high-performance concrete for the New Jersey Department of Transportation that would be used to rehabilitate bridges. If the compound can be produced at scale, it would greatly reduce the maintenance needs of some of New Jersey most critical transportation structures.

“For now, the commercial product is very expensive, about $3,000 per cubic yard” for UHPC, Meng said. “Just to compare, conventional concrete is about $100 per cubic yard.” So clearly, a cheaper compound with the same properties as UHPC would produce tremendous savings.

Meng and her team at Stevens have developed two versions of the new compound. One would be applied to pre-cast elements, such as girders. The other would cover the bridge deck.

The cost reductions are possible because the new compound uses inexpensive and locally available materials, according to Meng. The Stevens team increases the proportion of lower-cost ingredients in the mix, using cheaper sand and manufacturing byproducts, for example.

In addition, the researchers developed a process that produces a more tightly structured compound. “We use a particle packing model to optimize or maximize the particle packing density given the materials we use,” Meng said.

The mix and the process have worked in the laboratory, the next step is to try and scale up production to a commercially viable level. The Transportation Department will try out several plants and choose the facilities that will eventually produce the new UHPC.

When production is underway, the agency will apply the new compound to small bridges and monitor its performance. Meng said the  process should be completed in 2024.

While the Transportation Department is focused on bridges, Meng said the new UHPC could have other uses where concrete is a common material. In fact, she said, UHPC is already used in architecture around Europe.

“Because it is much easier to cast and it has much better durability … the UHPC could be working without repair for one hundred years,” Meng said. “Some prediction models on this is two hundred years, but just being conservative, I think one hundred years is a reasonable value.”

Meng has been working on other projects as well. She is using a $500,000 grant from the National Science Foundation to find ways to improve cement. And she’s basing her work on the properties of an unusual natural substance.

The grant, awarded under the Faculty Early Career Development program, is specifically aimed at making calcium-silicate-hydrate – the ingredient that makes cement, well, cement – even stronger. Meng’s research has focused on improving the crack resistance of cement modeled on the characteristics of nacre, or mother-of-pearl. Meng and other researchers at the Hoboken school, are employing a mesoscale assembly process to generate CSH mesocrystals layers, inspired by nacre, for cement-based composites.

Over the course of the five-year CAREER project, titled “Consecutive Assembly-and-Mineralization Processed Calcium-Silicate-Hydrate Nacre with High Specific Flexural Strength and Fracture Toughness,” the Stevens team will attempt to imitate the nacre growth process then test the resilience of the resulting compounds.

Meng is originally from China and received graduate and undergraduate degrees in civil engineering from Southwest Jiaotong University in Chengdu. After receiving her PhD from Missouri University of Science and Technology, she joined the Stevens faculty in 2018.

Engineering has always been a part of Meng’s life. “My father is a civil engineer,” she said. In fact, he also graduated from Southwest Jiotong University. “I think is a very impactful skill.”

While she had other offers, she chose Stevens because she felt welcome there. “When I talked to the department chair and the dean, I felt they would really support the young faculty,” Meng explained. “Stevens is like a family.”