World of Concrete, the world’s largest concrete trade show, just wrapped up in Las Vegas. A number of interesting applications of FRP composites, both carbon fiber- and glass fiber-based, were on view. What is FRP doing at World of Concrete? A variety of things, but many of them are hidden from view.
The use of carbon fiber for structural retrofit and repair of concrete is becoming more familiar. Glass fiber composite is more familiar to the construction world as a decorative architectural surface, not so much for its structural properties. But at WOC, there were glass fiber composites being used in innovative and unfamiliar ways for structural performance. It underscores as aspect of GFRP that is often forgotten: it’s really strong.
Spiderlath is a glass fiber lattice to be used instead of metal lath. It has strips of foam running through it to provide proper stand-off from the wall, so stucco or grout can establish strong mechanical bond. It does not corrode, is stronger than metal lath, and meets or exceeds all the requirements of ICC-ES AC 275 “Acceptance Criteria for Glass Fiber Lath Used in Cementitious Exteriior Wall or Exterior Plaster.” It can be used for installation of stone veneer, stucco, vertical carvings, floor overlays, and sculptures.
Denso North America offers a carbon-fiber reinforcement system for wood piles in marine applications. A cylindrical net of carbon fiber – nice and corrosion-proof – is placed around the column, and a wider fiber-glass column form around that. Then concrete is cast in the form, using the carbon fiber instead of steel reinforcement for the concrete.
For compromised concrete piles in marine environments, NRI offers a system of epoxy and carbon fiber wrapping.
Several manufacturers were showing fiberglass rebar for concrete. The value of corrosion-proof rebar is significant. Concrete in aggressive environments – think about a concrete sea-wall – gets destroyed from within by corroding rebar. Cracks in the concrete admit water, which causes steel to rust, and the rust is expansive. Ultimately it makes the concrete crack, flake and delaminate. GFRP rebar has not such problem. In addition to straight bars, column restraints are made of a continuous spiral.
Bridge decks are a particular concern, because they are very vulnerable to corrosion, and high in both monetary and social costs to replace. Aslan FRP sent us photos of a bridge deck demonstration project in Kansas. The I-635 Bridges over State Ave in Kansas City, KS, were replaced using traditional epoxy-coated steel reinforcement on the northbound bridge, and GFRP reinforcement on the soutbound side. (A cost analysis found that the price of GFRP rebar was competitive with steel, and the predicted service life considerably longer.
RJD Industries was showing a clever system of fiberglass form-ties for cast-in-place concrete walls. The corrosion-proof nature of these sacrificial ties means that they don’t bleed ugly rust down the side of a concrete building. Even though the ends of the tie may be visible, they blend into the concrete well, and their visibility remains discreetly limited to their own diameter.
Rockwell Window Wells was showing an item that in line with the more familiar architectural application of GFRP, a surface imitation of another material. But in this case, the unit is designed to be placed directly in the ground. Their window well creates a light well for a below0-grade window, and appears to be a stone retaining wall. However, the side view of the uninstalled unit reveals that it’s about 1/4″ thick, weighing dramatically less than stone and taking far less time to install.