Applications for carbon-fiber-reinforced polymers (CFRPs) have exploded in the last 30 years. These high-performance materials have long been used in the aerospace, marine and automobile industries. More recently, they have gained acceptance in the construction industry as a replacement for traditional structural reinforcement, with applications ranging from seismic strengthening of concrete columns and bridge girders to foundation reinforcement.
Todd Jackson, who is an associate member of ACI Committee 440 on Fiber Reinforced Polymers, says that CFRP materials are being used in place of steel because they offer numerous benefits. At the top of the list is their amazing tensile strength, which is well above that of steel.
“Carbon Fibers have an elongation of 1.5%, while steel has an elongation of 6%,” he explains. “So if you repair a wall with steel reinforcing, the wall could move in an additional 6% before the steel would come into play. If the wall is reinforced with Carbon Fiber Mesh, it won’t move in at all-the fiber material is much stiffer and virtually in tension when applied.”
Fortress Stabilization Systems’ Carbon Fiber/Kevlar mesh is pre-tensioned and pre-cured so that the tows remain straight. This ensures that the material will retain full strength. Once the mesh is encapsulated in the epoxy matrix, the strength is locked in. The fabric will not stretch, creep, or bend over time. Jackson acknowledges that the carbon fiber material won’t actually straighten a bowed basement wall, but it will prevent any additional inward movement.
Aesthetics are another reason more homeowners and contractors are opting to use CFRP systems. In most cases, a repair with Fortress Stabilization’s Carbon/Kevlar straps is barely noticeable because the material conforms to the wall and lies flat to the substrate. “If you cover the repair with paint, you won’t even know it’s there. You don’t have that option when stabilizing walls with I-beams,” says Jackson, noting that steel beams must be installed tied into the ceiling joists and foundation floor.
The Fortress Stabilization System can also be used in lieu of tiebacks, which generally must be anchored to dead-men buried in the ground 8 to 10 feet out from the wall. In restricted spaces or in neighborhoods where property lines are only 5 to 6 feet apart, they aren’t a viable option. “Carbon fiber repairs don’t require going into the next-door neighbor’s yard or excavation of property,” says Jackson.