With over 60% of the population in the United States now living in cities, most Americans find themselves surrounded by concrete. It makes up the pavement we walk on, supports bridges we drive over and is integral in the construction of homes, workplaces and schools. Yet, despite its reputation for strength, concrete is a very brittle product.
Concrete, although strong, cannot hold up under stress – because it is by nature immovable, it doesn’t take much movement to produce cracks. In minor works, this is an inconvenience, but not a serious problem. Cracks appear every few years, are repaired with new concrete, which will, in turn, crack again in the future. This cycle is costly but not considered to be hazardous. Unfortunately, when this kind of damage occurs in major infrastructure it becomes more serious. Cracks create weaknesses that are less able to withstand natural or man-made forces, such as earthquakes or terrorist attacks. When these events occur, the cracked concrete is more likely to experience structural failure.
Seeking a solution, a research team at the University of Michigan began looking at ways to make concrete that is less rigid and more pliable. They began their research by studying the properties of abalone shells. When examining the interior coating (known as ‘nacre’) they made a significant discovery: when viewed at the nanoscale, nacre looks much like a brick wall, composed of thin layers interspersed with a natural polymer which is highly elastic. This polymer allows the more rigid layers to move from side to side when under stress, and as a result, the nacre is incredibly strong, and yet quite flexible.
To replicate this effect, the researchers added tiny fibers into the traditional composite concrete mixture of sand, gravel, and cement. The inclusion of these fibers allowed the resulting concrete to imitate the ductile nature of the abalone shell; as a result, the concrete can distort under tension from 3-5% before failure occurs. This may not sound like much, but it actually increases the strain capacity of this product by 300-500%.
The significance of this “bendable concrete” (officially referred to as engineered cementitious composite, or ECC) cannot be overstated. If used in major infrastructure, this bendable concrete would be better equipped to endure the tensile strain of an earthquake or other disasters without fracturing into pieces. ECC is now being used in several large-scale projects in Japan for exactly this reason.
Beyond just preventing a catastrophic failure, bendable concrete has other benefits. It helps to prevent the minor stress cracks that are commonly seen in concrete structures, even going so far as to “heal” hairline cracks that do occur by a process of carbon mineralization. Researchers are even investigating ways this product may be able to neutralize air pollution in big cities.
Although bendable concrete has many advantages, researchers still need to look at whether it would pose challenges for other associated trades, such as plumbing or electrical works. But ECC undoubtedly has the potential to make US infrastructure more durable and safer for all.
Writer, Angel Content
Julie Adams is a versatile writer, marketer and innovation enthusiast born in Melbourne, Australia. Her years of experience in blogging has given her an eye for quality content, a mind for creativity and a passion for learning.