As with many other products and processes, biomimicry (learning and imitating the processes of nature) is transforming the world of concrete. Although in the early stages of being applied, concrete that is bendable without fracturing is now a reality. Concrete is the most ubiquitous building material on the planet, but it contributes 6-7 percent of greenhouse gases and is thus a major contributor to climate change. It has great compressive strength, but when it cures, it becomes a hard, brittle material.
The idea for bendable concrete is borrowed from nacre (mother-of-pearl), the material that lines the inside of abalone shells. The main material in nacre — small, hard bits derived from calcium carbonate — is made flexible by the natural elastic polymer that surrounds and ties these small chunks together. This combination makes nacre both strong and bendable.
A number of universities around the world, including the University of California at Irvine, Stanford, and the University of Michigan, have been investigating the nacre model for concrete. By eliminating the coarse aggregate from the mix (gravel, sand, and cement) and adding microfibers of silica, glass, steel, and/or polyvinyl, they approximate the flexibility of nacre. The interfaces between these tiny fibers and the cement recreate the controlled slippage in nacre. Bendable concrete, technically called engineered cementitious composite (ECC), is not a single design mix but a broad range of design mixes. The precision of these formulae comes from the application of micromechanics theory.