CAN SYNTHETIC FIBERS REPLACE WELDED-WIRE FABRIC IN SLABS-ON-GROUND?

Abstract

Reinforcing steel, such as welded-wire fabric (WWF), is often used to control cracks in concrete due to temperature and shrinkage stresses. WWF does not prevent concrete from cracking, but instead holds the cracks tight, maintains aggregate interlock and prevents faulting of the slab. Such reinforcement can also provide defined amounts of structural strength after the element cracks. Low dosages of low-denier fibrillated and monofilament-synthetic fibers are increasingly being used to replace conventional WWF. This study compares the performance of these synthetic fibers at low fiber content to that of a conventional WWF in order to determine how efficient the different reinforcement alternatives are in controlling the formation of plastic shrinkage cracks. The testing program also seeks to determine how efficient the reinforcements are in providing resistance to additional opening of cracks in hardened concrete after initial cracking has occurred in the slab. Six low-denier synthetic fibers, a coarse monofilament self-fibrillating synthetic fiber, a deformed steel fiber and a conventional WWF were studied. Compressive strength, average residual strength and round determinate panel tests were used to evaluate toughness. Results show that the use of low-denier-monofilament and fibrillated-synthetic fibers at low fiber dosages is more effective than the conventional WWF in controlling plastic shrinkage. However, the WWF significantly outperformed all low-denier-synthetic fibers in resisting crack opening in the hardened concrete. Both WWF and low-denier synthetic fibers mitigate cracking, but in different ways. The choice of reinforcement therefore depends on what performance is required. One solution may be to add the two products together in the same concrete to combine the properties of both the low-denier-synthetic fibers and the WWF.