Nearly 5,000 years ago, Egyptians used a kind of cement to construct the Great Pyramid of Giza. British bricklayer Joseph Aspdin obtained a patent in 1824 for Portland cement. But even after all these years, this foundational element of modern buildings, bridges, tunnels, pipelines, offshore wind farms, and other massive construction projects is still dangerously heavy to manage, posing a threat to construction crews—and prone to cracking, posing a threat to all of us who use these critical structures.
Weina Meng, assistant professor of civil engineering at Stevens Institute of Technology, has made it her mission to make cement-based material perform better. The National Science Foundation recently granted her a $500,000 Faculty Early Career Development (CAREER) award to address the challenge of transforming calcium-silicate-hydrate (CSH)—the ingredient that makes cement strong—to achieve unprecedented mechanical properties.
Early experiences put Meng’s civil engineering career on track
It’s a natural fit for Meng, who has spent nearly all her life observing, working with, and researching construction materials.
“My father is a civil engineer, and ever since I was three or four, he would take me with him to job sites to see how he built bridges and railroads, and tell me what they were doing,” she recalled. “Every summer, I’d work with him on construction sites, where I learned that what is most important is to ensure the quality of the materials and structures.”
Her current research was directly inspired by a nearly 330-foot long-span bridge her father had to place over a railroad track.
“An 8,800-ton bridge girder was precast along the railroad, and then it had to be turned 77 degrees and placed across the railroad overnight in a single night,” Meng said. “It was constructed with concrete and reinforced with steel, which made it very heavy, and very difficult and very dangerous to move. I thought if we could make a material that was strong but lightweight, it might help with construction time, and civil engineers like my father would be safer.”
After earning both her undergraduate and graduate degrees in civil engineering from her father’s alma mater, Southwest Jiaotong University, Meng came to the U.S. to focus her studies on creating sustainable and resilient concrete materials. She earned her Ph.D. in civil engineering from Missouri University of Science and Technology.
Since joining Stevens in 2018, she has been working on research to improve the crack resistance of cement-based materials to rival that of a surprising natural benchmark: nacre, or mother-of-pearl, a composite material made by some mollusks.
Making an abstract idea concrete—literally
“I have worked with a lot of professors, and one of them once posed a question about the possibility of making structures without steel bars,” Meng noted. “I think eliminating steel is an important part of transforming the design of structures and making them more durable. Cement-based concrete is easily damaged, and once that happens, harmful ions corrode the steel too. If we can eliminate the steel, we’ll solve some of the durability problems. Based on this, I spent more than six months reading science and nature papers day and night! Eventually I found that mimicking the architecture and chemical compositions of nacre could be a possible solution. I find that getting to a brand-new idea like this is more challenging than conducting research. Once you know the problem, you can always find solutions.”
That’s exactly what she will be doing in her five-year CAREER project, "Consecutive Assembly-and-Mineralization Processed Calcium-Silicate-Hydrate Nacre with High Specific Flexural Strength and Fracture Toughness." Meng and her team will mimic the growth of nacre by designing and controlling the development of CSH mesocrystals, then proving the high flexural strength and fracture toughness of the resulting, highly organized architecture.
“With its unique architecture, nacre is ultra-lightweight yet one of the strongest biomaterials,” she explained. “By studying the nanostructure of nacre, I noticed that it’s made of very weak calcium carbonate, or aragonite, but the way the aragonite combines with the organic materials created by the shell makes it strong. I thought that if we could create cement with a similar structure as nacre, we could tremendously enhance the resilience, sustainability, and durability of civil structural elements, while minimizing the need for reinforcement with steel bars.”
The project involves creating the methods to synthesize and control the growth; developing the process to scale the fabrication from small particles to half-inch squares; and characterizing, testing, and optimizing the mechanical properties of the multi-layered artificial structure. Key techniques will include freeze-casting, controlled mineralization, organic phase infiltration, and hot-pressing, while testing will be conducted through experiments, modeling, and machine learning. As a longer-term goal, the team will be working to accelerate the process from its current three-to-four-day cycle to one day, which will make scaling up more feasible. Sustainable structures for a stronger society
The development of this CSH nacre has the potential to transform the design, construction, and maintenance of engineering structures for sustainability.
“Its unprecedented mechanical properties would enable the fabrication of structural components with ultra-thin sections and ultra-high mechanical performance, while being aesthetically appealing,” Meng said. “This would mean accelerated construction and rehabilitation of buildings, bridges, and other structures with little or no steel reinforcement required, minimizing building materials, improving functionality, reducing maintenance costs, saving construction laborers’ lives, and enhancing the prosperity of our society.”
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