Carbon fiber is one of those futuristic-sounding, expensive materials that I associate with supersonic airplanes, fancy road race bicycles, and $400,000 dining tables.  So imagine my surprise when I found out that, back in 2003, a group of precast concrete companies banded together with carbon fiber grid provider Chomarat to form AltusGroup, who manufacture a product called Carbon Cast Concrete.  “AltusGroup members use Chomarat’s C-GRID®, as the carbon fiber epoxy based reinforcing in several precast building system products to enhance the strength and reduce the weight of precast concrete” (Drabestott).  Reinforcing humble precast concrete with glamorous carbon fiber seems a lot like parading Susan Boyle around in haute couture, but whatever it’s CARBON FIBER. 

Image credit www.bornrich.org

Carbon Cast concrete “uses conventional steel for primary reinforcing and C-GRID epoxy-coated carbon fiber composite grid for secondary reinforcing and shear transfer. This allows the material to be very lightweight compared to normal reinforced concrete” (Wright).  The C-GRID is made with continuous PAN (polyacrylonitrile) carbon fibers and epoxy resin — the same materials as carbon/epoxy golf clubs and aerospace parts. The carbon strands are chemically bonded together at the intersections with epoxy resin (AltusGroup). 

Images courtesy AltusGroup

So here are a few reasons Carbon Cast Concrete is great:

Non Corrosive: unlike typical steel reinforcing, the carbon fiber grid will not oxidize, nor will it cause rusting, staining or spalling.  This allows precast manufacturers to reduce the amount of concrete over the grid by up to three inches.  They use less concrete per panel, which reduces weight and raw material usage.  This also increases the durability of the concrete.

Light Weight: less concrete means lighter pieces – up to 50% lighter in wall panels and up to 8% in double tees.  Lighter weight components mean lighter structure, reducing costs for everything from transportation to construction cranes.  Lighter pieces also speed erection time because it’s easier and faster to maneuver them into position.

Thermal efficiency: carbon fiber grids improve thermal performance. Because carbon fiber has low thermally conductivity, it reduces the transfer of heat or cold from outside to inside. “The insulation embedded in the walls can deliver 100 percent of its rated performance without hot spots or cold spots. As a result, building owners can benefit from long-term energy savings and a smaller investment in HVAC equipment” (AltusGroup).

Here’s why you won’t be using it:

Cost: Carbon fiber grids costs about twice as much as the conventional steel reinforcing it replaces.

WU XING:

I’m filing Carbon Cast Concrete under EARTH because of the carbon.

Cited:

Drabenstott, Michael. “Carbon Fiber Growing as Reinforcing Material in Precast Concrete.” Carbon Fiber Gear Blog.  Accessed 06/25/10.  URL.

Wright, Fiona. “Carbon Cast Concrete.” EzineArticles.com. Accessed 06/25/10.  URL.