Transmaterial

Bendable Concrete

University of Michigan has developed a new type of fiber-reinforced bendable concrete which looks like regular concrete, but is 500 times more resistant to cracking and 40 percent lighter in weight. Tiny fibers that comprise about 2 percent of the mixture's volume partly account for its performance. Also, the materials in the concrete itself are designed for maximum flexibility. Because of its long life, the Engineered Cement Composites (ECC) are expected to cost less in the long run, as well.

Traditional concrete has many problems including the lack of durability and sustainability, failure under severe loading, and the resulting expenses of repair. U-M's Victor Li believes that ECC addresses most of those problems. The ductile, or bendable, concrete is made mainly of the same ingredients in regular concrete minus the coarse aggregate, Li said. It looks exactly like regular concrete, but under excessive strain, the ECC concrete gives because the specially coated network of fibers veining the cement is allowed to slide within the cement, thus avoiding the inflexibility that causes brittleness and breakage, Li said.

Fiber-reinforced concrete is not new, but Li believes that U-M's ECC - under development for the past 10 years - is vastly superior to other fiber-reinforced concretes in development today. The key is that ECC is engineered, Li said, which means that in addition to reinforcing the concrete with microscale fibers that act as ligaments to bond the concrete more tightly, scientists design the ingredients in the concrete itself to make it more flexible.

"The broad field of micromechanics has tried to understand how composite materials behave," Li said. "We went one step further and used the understanding as a material design approach in the development of ECC." [Excerpted from the University of Michigan website; suggested by Shawn Gehle, Kansas City.]

posted by Blaine @ 2:01 PM