New fiber reduces long-term concrete cracking by 40%
High-performance crack-fighting PVA fiber introduced by Nycon and Kuraray

October 31, 2005

Westerly, RI and New York, NY

Nycon, Inc., and Kuraray America, Inc., announce a new high-performance PVA structural fiber reinforcement for concrete called KURALON RSC. At a dosage of one pound per cubic yard of concrete, KURALON RSC (i.e., reduction of shrinkage cracking) reduces long-term drying shrinkage cracking in concrete by 40% or more. The crack reduction resulting from RSC reinforcement represents a 50% 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 long-term 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 tend to 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 to 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 RSC 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. He had this to say about KURALON RSC: “The PVA 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 PVA-reinforced 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 (see attached graphic). Stork/Twin Cities Laboratories of St. Paul, MN has established that the RSC at a dosage of 1 lb per cubic yard meets or exceeds the ICC AC32 requirements (see attached).

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 is the sole distributor of KURALON PVA fibers in the U.S.

Kuraray America, Inc., a division of Kuraray Company, Ltd, manufacturer of KURALON fibers, is a leading science and technology company providing innovative chemical, plastics, medical and textile products and services to industrial and consumer markets worldwide. With annual sales exceeding $2 billion, the 76-year-old company has more than 8,000 employees servicing customers through more than 70 subsidiary companies worldwide.

Kuraray Okayama Plant

Attachments:
Bar graph showing long-term crack control
Stork Twin City Testing Data - ICC AC32 Certification of Compliance
Project Profile – Excel Car Wash

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