Concrete reinforcing fibres offered cheaper

Tom Shelley reports on an alternative source of polymer fibres to dramatically improve the mechanical engineering properties of concrete

Following the publication of our article in the January edition of Eureka, "Polymer fibres make flexible concrete to withstand earthquakes", it has been brought to our attention that a company in Pakistan has for some time been producing a similar fibre product which it sells for the princely sum of £1.80/kg. Syntech Fibres produces a fibre called "Duracrete", which consists of 13mm to 50mm long polypropylene fibres, which were initially developed to prevent shrinkage cracks leading to reinforcing bar corrosion, a particular problem in marine environments including parts of the City of Karachi where the fibres are made. Managing Director Hamid Omar told us that the exact formulations used, including the crucial coatings, are the results of, "Lots of experiments." Different grades are supplied for different purposes, with 'hard' grades for engineering concrete and 'soft' grades for reinforcing plaster. As in the US-Japanese studies, the fibres have a dramatic effect on mechanical properties. Impact strength of concrete is 14 times greater with fibres than without, flexural fatigue strength is 30 per cent greater, and load carrying deflection prior to failure about 70 times greater giving a vastly increased flexural toughness. Test results cited were produced by the South Dakota School of Mines and Transportation in the US. Recommended dosage is about 0.6 to 1.8kg of fibres per cubic metre of concrete depending on the nature of the work. The fibres may be supplied in bulk or in small 100g or 150g bags to be added as one bag per bag of cement. Syntech Fibres