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.

Concrete Masonry Units, also affectionately called “CMU,” provide those fortunate enough to be able to lay hands on them with an easy, fire-resistant, low maintenance, cheap way to throw a wall together in a hurry.  All that’s needed is a foundation, the aforementioned CMU, reinforcement, mortar, concrete to fill the voids in the blocks where necessary, and somebody with a strong back to put it all together.  Convince your somebody to stack these ingredients evenly in neat rows – and voila!  You have a wall.  You can even cover up CMU with something else if they look ugly.  So where’s the drawback?

According to the Portland Cement Association, “the standard concrete block is a rectangular 8X8X16-inch unit (200X200X400 mm) made mainly of portland cement, gravel, sand, and water. The concrete mixture may also contain ingredients such as air-entraining agents, coloring pigment, and water repellent” (Source: PCA).  While cement is in many ways an exquisite material, it is also energy intensive to produce.  It’s also subject to price volatility due to fluctuations in demand, although I read somewhere that right now it’s being consumed by humankind in larger quantities than water.*

One solution to the problem of too much cement in one’s concrete walls is to bulk the mixture up with a large quantity of dirt.  Rammed earth construction and adobe are two alternatives that use soil composites and recycled rock materials – often from the very site on which the construction occurs (local is good).  This construction technique produces absolutely gorgeous, thick, luscious walls with amazing striations running through them.  Of course, the look is a bit “unconventional” and this might make it tricky to finance the construction in say, a pseudo-Victorian duplex development.  The other problem with this type of construction is that not every Tom Dick or Harriet knows how to do it.

Integrity Blockhas attempted to take the convenient aspects of a unitized masonry construction system and combine them with the earth-friendly, dirt-filled characteristics of rammed earth construction.  Integrity Block’s building blocks are made out of a super-secret proprietary soil composite that contains pre-consumer recycled content (waste material from mining and quarrying operations). The manufacturing process consumes 40 percent less energy and emits 39 percent less carbon (Source: Edmonds).  While the goal is to cut cement out of the formula for the blocks at some future date, right now there is 40% less cement than in traditional CMU (Source: Schwartz).

So here are some reasons why Integrity Block has all the makings of awesomeness: the super-secret proprietary soil composite is formulated such that blocks come in earthy colors like brown or gray; the blocks come in standard sizes, and they meet typical CMU performance standards and established codes.  Anyone (by which I mean almost everyone) who can lay CMU will be able to work with Integrity Block.  I can practically smell the LEED credit.

As far as I can tell, Integrity Block distributes its product only in Northern California, in order to keep the old carbon footprint low, but they’re trying to expand production across the United States (Source: Edmonds).  Let me know if you’ve used this product and describe the experience, if you’re inclined.

The large quantity of soil that has crept into these blocks make assigning them to the Earth category something of a no-brainer.  I wonder how they would perform in a marine environment – I’m picturing a sea-side marsh in Georgia, for example.

Cited:

“Concrete Masonry Units.”  The Portland Cement Association.  Accessed 01/29/10. URL.

Edmonds, Molly.  “What’s so Special about Integrity Block?” HowStuffWorks.com.  Accessed 01/26/10.  URL.

Schwartz, Ariel.  “10 Green Startups to Watch” FastCompany.com 11/10/09. Accessed 01/26/10. URL.