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Sharp price increases for steel reinforcing in the international market place have resulted in designers, contractors & builders looking for construction solutions that involve using less steel. Market analysts point to extraordinary consumption
of steel by China as reasons for the increased global prices. For
example a supplier of steel market information, MEPS
International reports price hikes between February 2003 and
February 2004 as high as 65 percent in the North American market
and the situation is similarly reported in Europe. The market is so volatile at the moment that some steel suppliers are refusing to quote prices until time of delivery and worse still in some areas contractors are simply unable to acquire the steel they need for their projects and lengthy site delays and even complete standstills have been reported. For those seeking alternatives to steel a solution may be found in innovation. Since 1997 Japanese construction companies have been using Structural synthetic fibres to replace steel mesh and steel fiber reinforcements and the technology has since spread into Australia, Europe and North America. Originally conceived for the reinforcement of concrete pavements
the fibres have also seen use in areas such as sprayed concrete linings
in mines and tunnels, marine structures, housing construction and
precast concrete.
A big reason for the fibres acceptance is its ease of use, you can simply throw the bags into the truck mixer and the concrete is reinforced with approximately 1 million little reinforcing bars, thereby reducing labour costs and also alleviating health & safety issues surrounding the handling and placement of steel reinforcement products. Also the structural synthetics are corrosion free and have proved to outperform steel in long term durability tests on cracked concrete.
In the past there has been some negative publicity surrounding plastic fibers purportedly used in concrete for ‘plastic shrinkage’ reinforcement but the technology surrounding the structural synthetics is quite different. |
The post cracking performance of different reinforcements can be accurately
compared using the ASTM C-1550 round panel test and indications are that the
synthetic fibres can at least hold their own against conventional welded wire
mesh or steel fiber and therefore rate as a suitable alternative for many reinforced
concrete applications. To compare reinforcements using the ASTM C-1550 round panel test concrete discs of 800mm diameter x 75mm thick are prepared using the different reinforcing materials.
The disc is then supported
on 3 radial pivots inside the testing rig and a point load is applied
at the centre of the round panel which travels through a total central
deflection of 40mm and cracks the specimen.
Some recent projects using structural synthetic fibre include: For more information: www.elastoplastic.com
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