The rising cost of conventional steel reinforcement has dramatically increased the demand for synthetic, as well as steel, ï¬bers as an alternative to wire mesh in shotcrete applications. More importantly, with the shift to the shotcrete industry is discovering that reinforcement yields signiï¬cant economic advantages, as well as definite engineering benefits for long-term shotcrete durability.
Signiï¬cant economic beneï¬ts result from the elimination of placing wire mesh. In addition, the use of ï¬brous reinforcement in lieu of wire mesh reduces rebound from the receiving face by up to 20%.
Suitable shotcrete applications include slope stabilization, tunnel liners and water diversion channels, structural repairs, swimming pools, arti-ï¬cial rock, waterscapes, and thin overlays. These applications beneï¬t from the three-dimensional network of reinforcement formed by the ï¬bers, which reduces plastic shrinkage cracking and drying shrinkage cracking. The ï¬bers also provide quanti-ï¬able toughness and enhanced durability, including increased surface abrasion resistance and impact resistance. Performance is predicated on the proper selection of the ï¬ber type, length, conï¬guration, and addition rate. Elimination of potential voids created by the wire mesh pattern is just one more advantage of using ï¬ber.
General Product Information
There are three ï¬ber types that contribute to the physical properties of shotcrete: steel ï¬bers, micro- synthetic ï¬bers, and macro-synthetic ï¬bers.
Although the price of steel ï¬bers has risen, the fact remains that the in-place cost of steel ï¬ber-reinforced shotcrete is less than the cost of ï¬xing and placing conventional steel. In general, steel ï¬bers must meet the requirements of ASTM A 820 and may be manufactured from either drawn wire or slit sheet steel. Steel ï¬bers, ï¬rst introduced in the mid 1970s, are generally available in four lengths: 3/4, 1, 1-1/2, and 2 in. (20, 25, 38, and 50 mm). The standard unit of sale is typically 50 lb (22.7 kg) boxes or bags.
Micro-synthetic ï¬bers can be nylon mono-filament or polypropylene monofilament and ï¬brillated ï¬bers. They have been in use since the early 1980s for secondary temperature-shrinkage