Dear Sir
I refer to John Greenhalgh’s article in September’s issue of T&TI “Performance of fibres for concrete”. I can offer to clear up some of the “confusion” he refers to about fibre choice by updating some of the information contained in that article. The references to structural synthetic fibres (SSF) – particularly their performance relative to steel fibre – may have been true three years ago, but the swift engineering advances still underway in plastics technology have vastly changed the current situation.
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There is not much to be learnt from studying a graph such as Figure 1 in the article, which plots residual strengths versus fibre fraction by volume. When the comparison between SSF and steel fibre is evaluated for a particular project, it is almost always price per cubic metre of concrete reinforcement to achieve a specified performance that is the yardstick.
Several SSF producers are now offering products that equal, or better, the best performing steel fibres on offer. For example, in a recent trial on a Norwegian Tunnel project, 8kg of Barchip Kyodo fibre (SSF) achieved 1141 Joules compared to 35kg of hooked end steel fibre, which achieved 1127 Joules. These are rather different outcomes to the article’s asserted performance levels of SSF of between 24% – 50% of steel fibre.
The statement that there is little detailed information available regarding the behaviour of SSF in fire and creep is similarly true of steel fibre. The advantages of the synthetic fibres over steel fibre, such as non-rusting, lighter and easier to handle and competitive cost/toughness, have to be weighed up for each project, taking into account price, end use and client’s specification.
The structural synthetic fibre industry has proven itself over the last six years in various mining, tunnelling and civil applications and, with the current pace of development, the future looks very encouraging. As Mr Maguire says to Ben (played by Dustin Hoffman), in that famous Hollywood scene from “The Graduate”, “There is a great future in plastics”.
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By GlobalDataAndrew Ridout
Elasto Plastic Concrete (Europe) Ltd
