New methods of reinforcement

Press, 6 May 1983, Page 16

New methods of reinforcement

Concrete reinforced with polypropylene fibres has many advantages over steel: polypropylene is cheaper, has a high stress factor and does not rust. Since the late 19605, M. J. McKendry, Ltd, has followed with interest the development of polypropylene fibres. They knew that this material, if it met the industry and their own standards, would offer many advantages in the reinforcing of small thin-walled, precast concrete products. The late Mr M. J. McKendry was enthusiastic about the use of the polypropylene reinforcement in concrete but cautiously delayed its introduction until he could confidently offer finished

products which were of higher quality than those being manufactured. Research continued through the 1970 s but it was not until recently that McKendrys believed that they knew enough about the material to change their specifications for the manufacture of some of their products. As a further check, Mr Dick Sullivan, an independent consulting engineer, was asked to test the product. The results showed that polypropylene is chemically more inert than concrete. Any chemicals which attack the fibre will also attack the concrete. Polypropylene, in the form of fibrillated tape cut to a predetermined length and added to the concrete mix, quickly disperses itself through the mix. Although polypropylene can be handled in a similar manner to ordinary concrete, external vibration of the forms is recommended. Cured concrete with fibrillated polypropylene reinforcement, which is added in correct length and proportions, will have: Higher impact resistance. Cracking will not reduce the strength of the product.. Reinforcement will not deteriorate from chemical attack.

With this'product knowledge, McKendrys has confidently changed to using fibrillated polypropylene fibre, with a nominal amount of mild steel reinforcement, in their troughs. Because manufacture is quicker and less steel is used, the final product is now much more competitive.

McKendrys also markets packed bags of polypropylene. These packs (to the size required) are sold throughout the country.