Concrete is an extremely strong building material, but has a notoriously weak tensile strength. In order to resist tension, bending, and shear forces, steel rebar or other reinforcement materials are added either prior to the placement or into the mix. Even with reinforcement, concrete is still extremely rigid and prone to cracking. In the event of a major earthquake, the uneven and horizontal forces can cause structures to crack and, in the worst case, cause failure.
To help keep buildings and their occupants safe in major earthquakes, researchers at the University of British Columbia have discovered a spray-on concrete reinforcement that greatly improves concrete’s resistance to earthquakes up to a magnitude of 9.1.
Concrete walls are sprayed with the reinforcement, which is made up of “polymer-based fibers, flyash, and other industrial additives,” in a 0.4 inch (10mm) thick layer. The retrofit reinforcement allows the concrete to bend with the movement of the earthquake, making it much more ductile.
The product is being called Eco-Friendly Ductile Cementitious Composite, or EDCC, due to its heavy reliance on flyash, with is an industrial byproduct of coal.
“By replacing nearly 70 per cent of cement with flyash, an industrial byproduct, we can reduce the amount of cement used,” said UBC civil engineering professor Nemy Banthia in a press release. “This is quite an urgent requirement as one tonne of cement production releases almost a tonne of carbon dioxide into the atmosphere, and the cement industry produces close to seven per cent of global greenhouse gas emissions.”
This is an extremely interesting product to me, because, traditionally, reinforcement has always been added prior to the concrete placement or within the concrete mixture. Since this material is meant as a retrofit for existing walls, it can help save many lives in the event of an earthquake, because it won’t require extremely expensive and time consuming demolition and rebuilding of exterior walls on at-risk structures. Imagine the impacts retrofit reinforcement could have on failing infrastructure around the world.
Within the next couple months, EDCC will be installed in its first official real world application at the Dr. Annie B. Jamieson Elementary School in Vancouver, Canada.
In the video below, you will see an unreinforced wall be put under intense pressure equivalent to a 9.1 magnitude earthquake and then the retrofitted with EDCC wall withstand that same amount of pressure:
Full story: UBC researchers develop earthquake-resistant concrete | UBC