A major source of bridge deterioration requiring constant maintenance is mechanical expansion joints installed between adjacent simple span bridge decks. This project utilized patented U-M developed ultra-high ductility “bendable concrete” in a bridge deck over I-94 in Ypsilanti, Michigan. The concrete is not only durable but also self-repairing.
Number of bridges in the US
Number of bridges that are "structurally deficient”, having at least one key structural element in poor condition
The number of times Americans cross these structurally deficient bridges each day
In 1889, the Lake Alvord Bridge, the first reinforced concrete bridge in the United States, was built in San Francisco. The first concrete street in the United States was built in 1891 in Bellefontaine, Ohio.
Fabrication of concrete is a multistage process that uses considerable energy. The binder in the majority of concrete, Portland cement, is made by grinding together limestone (for its calcium content) and clay (for its silicon content) into powder, then heating the mixture in a kiln to more than 1,450 degrees Celsius. At such high temperatures, the molecules from each material diffuse into each other, in a process called sintering. The resulting solid pieces, called clinker, are then ground again with other trace materials. To make concrete, cement is mixed with an aggregate—such as gravel and sand—to give it structure, then water is added.
Standard concrete is brittle and will crack under tension. For concrete construction, brittleness is also synonymous with cracks and deterioration. Over the past two decades, University of Michigan researcher, Victor Li, has developed a ductile concrete known as Engineered Cementitious Composite (ECC), popularly known as “bendable concrete.” The primary reason for ECC’s high performance is the ability of it to strain-harden under uniaxial tension while forming diffused microcracks. ECC has an ultimate strain capacity typically over 4% which is over 400 times that of normal concrete!
Within the United States, a major source of bridge deterioration requiring constant maintenance are mechanical expansion joints installed between adjacent simple span bridge decks used to control deck cracking when the bridge span is subjected to expansion and contraction due to temperature cycles. Bridge deck cracking allows salt and water to contact reinforcing steel, thereby causing corrosion through steel oxidation and concrete cover spalling, and ultimately leading to structural failure. Typical to many regional and state departments of transportation within the US, the State of Michigan Department of Transportation (MDOT) has actively sought engineered and constructed solutions to the expansion joint problem.
An ECC, “bendable concrete”, demonstration project, in cooperation with the Michigan Department of Transportation, was completed during summer 2005 on the Grove Street Bridge crossing I-94 in Ypsilanti, MI. The 225 mm thick ECC link measured 5.5 m by 20.25 m. Construction included 25.5 m3 of ECC, delivered on-site by standard ready-mix concrete trucks from a nearby batching plant. Construction of the demonstration bridge took place in two phases to allow for continued use of the bridge during construction.
Now, nearly 15 years after this ECC link slab was installed, the performance of this link slab remains unchanged showing little sign of traditional wear. With further long-term performance monitoring and additional demonstration experience, ECC link slab can be an effective replacement of conventional expansion joints resulting in significantly reduced bridge deck maintenance needs.
Figure 9.22: Condition of ECC link-slab (a) immediately after construction and opening to traffic in 2005 and (b) in 2015. Apart from light abrasion on the surface of the link-slab, the condition remained about the same after ten years of use.
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James R. Rice Distinguished University Professor of Engineering
E. Benjamin Wylie Collegiate Professor of Civil Engineering
Professor of Civil and Environmental Engineering
Professor of Materials Science and Engineering
Professor of Macromolecular Science and Engineering
Dr. Victor Li is the James R. Rice Distinguished University Professor of Engineering, and the E.B. Wylie Collegiate Professor of Civil Engineering at the University of Michigan, Ann Arbor. His research interest is in multifunctional materials targeted at enhancing civil infrastructure sustainability and resiliency. He led the research team that invented Engineering Cementitious Composites, popularly known as “Bendable Concrete”. Professor Li was awarded the International Grand Prize for Innovation by the Construction Industry Council and the RILEM Life-time Achievement Award in 2016. He received the Distinguished Graduate Mentor Award in 2015 and the Distinguished Faculty Award in 2006 from the University of Michigan. In 2005, he received the Stephen S. Attwood award, the highest honor bestowed by the College of Engineering at the University of Michigan. In 2004, Professor Li was honored by the Technical University of Denmark with a “Doctor technics honoris causa” in recognition of his “outstanding, innovative contributions to materials research and engineering and providing our society and the construction industry with new, safe and sustainable building materials”. Professor Li is a Fellow of the American Society of Civil Engineers, the American Society of Mechanical Engineers, the World Innovation Forum, and the American Concrete Institute. His research and societal impacts have been featured in the CBS Evening News, CNN, the Discovery Channel, the Architectural Record, the American Ceramic Society, the Portland Cement Association, and the Forbes Magazine, amongst many other public media. Professor Li is named inventor on ten US patents.
Watch Victor Li testify to the Michigan House of Representatives Appropriations Subcommittee on Transportation discussing the potential benefits of using bendable concrete on Michigan roads and bridges.