Polypropylene fiber bundle for manufacturing ductile concrete. Photo by Empa Switzerland.
Concrete is an omnipresent material within the constructed environment, and over one cubic meter is made annually for every person on earth. Although concrete was originally invented by the Romans from pozzolan, aggregate, and quicklime—called opus caementicium—it wasn’t until the integration of steel reinforcement that concrete really took hold in the construction industry. Reinforced concrete became one of the primary materials in modern building as a result of its strength, adaptability, and ease of manufacture.
Despite its widespread acceptance (or perhaps because of it), reinforced concrete continues to change. Researchers studying various failure modes in concrete are modifying the recipe in pursuit of a lighter, stronger, and more durable building material. One popular new technique is the replacement of steel with other types of reinforcement such as carbon or glass fibers, which are more resistant to rust and require less insulation than steel reinforcing.
Recently, scientists at Empa Swiss Federal Laboratories developed a more ductile type of concrete using polypropylene fibers. The new concrete is more lightweight and economical than conventional reinforced concrete. According to lead researcher Josef Kaufmann, “We use five kilos of synthetic fiber to replace thirty kilos of steel fibers, and at the same time our bicomponent fibers cost about ten percent less than conventional steel fibers.”