This new form of concrete uses microfibers in the place of coarser bits of sand and gravel that traditional cement mix uses. The fibers allow the final composite to bend with minimal fracturing and if fracturing does occur, the cracks tend to be less than 50 microns wide. When these tiny cracks form, the dried concrete absorbs moisture from the air. When it does this, the concrete in the crack becomes softer and eventually "grows" until the crack is filled in. At the same time, calcium ions within the crack absorb the moisture along with carbon dioxide from the air. This reaction forms a calcium carbonate material that is similar to the material found in seashells. This regrowth and solidifying of calcium carbonate renews the strength of the cracked concrete.
The rigidity of traditional concrete leads to the formation of large cracks that can seriously degrade the integrity of important structures. Furthermore, when damage does occur to concrete, expensive and resource-consuming measures must be taken to repair the concrete, usually from the outside. Or, if repair measures are insufficient, the structure must be demolished and rebuilt which further expands the need for resources. This new cement composite, while currently three times the price of traiditonal concrete, promises to pay for itself with reductions in repair costs over the lifetime of the structure.
Self-healing and self-repair is a common theme in biological systems from trees to human skin. The less severe the damage is to an organism, the easier it is for the organism to repair itself and for the repair to be strong and long-lasting. These Engineered Cementitious Composites mimic natural systems in their structure by minimizing damage when it does occur, which leads to the ability to repair themselves quickly and effectively.