JEC COMPOSITES MAGAZINE - Issue #38 - January/February 2008 - 26

BUSINESS Niche market Carbon fibre grid improves precast concrete While carbon fibre is universally acclaimed for its strength as a primary material – witness its use in aerospace, automotive and wind energy applications – carbon fibre also has a remarkable capacity to make other materials stronger. The same high-strength characteristics that make it desirable for demanding applications render it ideal as a reinforcing material. Nowhere is this property more evident than with concrete. manufactured in a factory and then shipped to a job site for erection. In 2005, five precasters along with C-GRID™ manufacturer TechFab LLC formed AltusGroup, a partnership dedicated to expediting the development and commercialization of precast concrete using C-GRID carbon fibre grid reinforcing. Because precasters’ market areas are limited by the cost effectiveness of transporting the heavy concrete pieces, their willingness to share the technology with other AltusGroup members enabled the development of the building industry’s first-ever national brand of precast concrete in the United States: CarbonCast. Since introducing the technology nearly four years ago, AltusGroup members have realized significant progress in promoting the acceptance of carbon fibre grid reinforced precast concrete. It has been used on nearly 200 projects ranging from 30-storey condominiums to 75,000seat sports arenas. events, and wind loads. It typically takes the form of rebar, prestressing strand, or post-tensioning cables. Secondary reinforcing – usually a mesh or grid, or occasionally loose fibres placed in the mix – controls cracks caused by shrinkage or thermal loading on the surface. In terms of rebar and mesh, common carbon steel is the least expensive material, though its price is rising. Carbon steel is strong and generally easy to work, but it still rusts, even when galvanized or epoxy coated. When steel corrodes, it doubles in volume, causing cracking or spalling. When wet, it may also cause staining. Naturally, any cracks in the concrete will accelerate the ingress of moisture, causing even more havoc. As a result, a structure’s performance and aesthetics suffer over time. Nonetheless, for decades steel has been the reinforcing material of choice for precast concrete. Until recently, no other material made major inroads. Advancements in industrial-grade carbon fibre production have made it a costeffective alternative to steel mesh reinforcing for precast concrete structures. Reinforced precast products manufactured with epoxy-coated carbon fibre grid are extremely competitive from a cost perspective with conventional precast products that employ steel mesh for secondary reinforcement. Carbon fibre effectively eliminates concrete cover requirements, enabling new precast JOHN M. CARSON DIRECTOR COMMERCIAL DEVELOPMENT TECHFAB, LLC s a replacement for conventional steel reinforcing, carbon fibre grid can dramatically improve many aspects of concrete performance. It had been used primarily in concrete for rehabilitation applications, everything from bridge decking to balcony repairs to industrial floor retopping to roof renovation. It delivered outstanding resistance to corrosion, adding years of durability to the projects. Several forward-thinking companies have explored the initial use of carbon fibre grid in precast concrete for large concrete elements such as facade panels, walls and parking garage components that are Why precast concrete needs reinforcing Concrete is strong in compression but weak in tension. Reinforcing steel compensates for this weakness, but it requires extra concrete covering it to develop its strength and to help protect it from the elements that cause corrosion. There are two types of reinforcing: primary and secondary. Primary reinforcing resists tensile stresses induced by external loads, such as gravity, seismic The Macro Fibre Composites actuator JEC Composites Magazine / No38 January - February 2008

JEC COMPOSITES MAGAZINE - Issue #38 - January/February 2008

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #38 - January/February 2008