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news
August 2005
Westerly, RI and New York, NY
Nycon, Inc., and Kuraray America, Inc., announce a new high-performance PVA structural fiber for concrete called Kuralon RSC15*. At a dosage of one pound per cubic yard of concrete, Kuralon RSC15 can reduce long-term drying shrinkage cracking in concrete by 40 percent or more. Independent tests show the crack reduction resulting from Kuralon RSC15 reinforcement represents a 50 percent improvement over polypropylene fibers at only half the dosage.
The breakthrough in crack reduction comes from a newly engineered PVA fiber that generates a molecular bond strength between the PVA fiber and concrete that is 300 percent greater than that of polypropylene, fiberglass or steel fibers.
Compared to these other fibers, PVA fibers are significantly better at preventing longterm cracking because of their improved bond strength with concrete. Both steel and glass have high tensile strength, but low bond strength with concrete and mortars. As concrete dries, these fibers can slip out, losing the benefit of their tensile strength. PVA fibers, on the other hand, form a molecular bond with the concrete during hydration. With their low elongation and ultra-high bond strength, they are not easily pulled from the concrete.
A high modulus of elasticity is another factor contributing to the reinforcing effectiveness of Kuralon PVA fibers. “Typically, polypropylene fibers are used to reduce early plastic shrinkage,” says Richard McCabe, Senior Advisor for Kuraray America. “After 24 hours their work is largely done because their modulus of elasticity is less than that of concrete. That means they are ‘stretchier’ than concrete, where a true structural fiber is as stiff as the concrete it reinforces.”
Other PVA fiber characteristics include a high resistance to alkali environments exceeding that of polypropylene or glass fibers. They are highly abrasion-resistant and, with a density of 1.3, they also finish nicely.
Kuralon RSC15 fibers come prepackaged in disposable one-pound bags or larger and can be added at the ready-mix plant or on the job site. Normal mixing time is three minutes.
Ed Dornn, owner of Excel Design and Construction, used PVA fibers for a 10,000 square foot car wash in the harsh conditions of Brandon, Manitoba Canada. He had this to say about Kuralon RSC15: “The Kuralon fibers were used to produce a durable mix that would hold up under heavy load, exposure to chemicals and moisture, and the extreme freeze/thaw cycles typical of Canadian weather patterns. We needed a
reinforcing fiber that would create a tough surface and prevent delamination—one that would minimize shrinkage cracking, permeability, and spalling of the slab. The fibers really performed very well: The workability, placement, and finishability of the PVAreinforced mix was very good. The fibers played an important role in preventing the aggregates and fines from settling out. The fines, which tend to rise to the surface and weaken it resulting in shrinkage cracking, were tied up in the matrix. Even with vibration, the mix stayed together with no segregation of the aggregates. We are very excited about the high performance of PVA reinforcing fibers in Canada’s unforgiving winter climate.”
Test results for the new PVA fiber were performed by Concretum Construction Science, AG, of Zurich, Switzerland. Stork/Twin Cities Laboratories of St. Paul, MN has established that Kuralon RSC15 at a dosage of 1 lb per cubic yard meets or exceeds the ICC AC32 requirements.
Headquartered in Westerly, Rhode Island, Nycon, Inc., is a global supplier of synthetic and steel reinforcing fibers for concrete and mortar applications. Established in 1985, Nycon distributes Kuralon PVA fibers in North America.
Kuraray America, Inc is U.S. subsidiary of Kuraray Co. Ltd., the manufacturer of Kuralon PVA fibers. and a leading science and technology company providing innovative chemicals, fibers and diversified products. With annual sales exceeding $3 billion US dollars worldwide, the 79-year-old company has approximately 6700 employees servicing customers through more than 80 affiliated companies in Japan and overseas.
N.B. RSC is the abbreviation for reduction in shrinkage cracking.
PVA is the abbreviation for polyvinyl alchohol.
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