Concrete is the second-most-used material in the world, after water. Yet for all its utility, conventional concrete comes with significant downsides. Given its volume, concrete is quite heavy, and its vulnerability to cracking often limits service life to less than 50 years. Moreover, concrete manufacturing generates about 8% of human-related global carbon dioxide emissions.

Taking concrete to new levels of lightness, durability and sustainability is the goal of Weina Meng, an associate professor of civil engineering in Stevens’ Charles V. Schaefer, Jr. School of Engineering and Science. A leader in the field of ultra-high-performance concrete (UHPC), she is working on optimizing UHPC mix designs to fully deliver on its promise for large-scale building projects while also bringing down costs.

“The mechanical properties and durability of UHPC are much better than ordinary concrete,” says Meng. “UHPC materials can achieve over 100 years’ service life, making UHPC an ideal material for sustainable and long-lasting infrastructure.”

Economical, Enduring and Eco-Friendly

A prime application for UHPC is in bridge deck repair and rehabilitation. Because UHPC is so dense and strong, a thin layer of just 1 to 2 inches can take the place of 5 to 8 inches of conventional concrete, dramatically reducing the load on existing structures and thus boosting bridge lifespans.

Starting in 2019, Meng partnered with the New Jersey Department of Transportation and Rutgers University to develop lower-cost UHPCs that still maintain their desirable traits. Meng succeeded by crafting formulas in her Stevens lab using materials sourced locally in New Jersey, slashing costs to one-third of commercially available UHPC, down to about $1,800 per cubic yard. The state has already started rolling out this “NJ UHPC” on bridge projects.

As a bonus, Meng’s new UHPC has exhibited lower “shrinkage” than normal, which translates to even greater service life. As fresh-poured concrete dries, water in internal pores evaporates and the material can form tiny cracks, setting the stage for future deterioration. To mitigate this shrinkage, Meng and colleagues are devising novel mixtures. They reported in a recent study in Concrete and Building Materials how to produce early-crack-free UHPC, courtesy of certain ratios of lightweight sand, expansive agents and shrinkage-reducing ingredients. “We are developing technologies for lightweight, sustainable and low-shrinkage UHPC,” Meng says.

In an accompanying study, Meng and co-authors showed that adding biochar — a charcoal-like waste product — to UHPC mixes can also enhance strength, lower shrinkage and helpfully sequester carbon dioxide. To further guide the optimization of UHPC, the researchers have started employing AI-driven programs, as reported in a June 2024 study.

Overall, the innovation in Meng’s lab continues apace. “We are exploring unique material properties and resolving practical problems with UHPC,” Meng says. “This material holds so much promise.”

– Adam Hadhazy