Q. Can synthetic fibers replace welded wire reinforcement in nonstructural slab-on-ground construction?
A. ACI 302.1R-04, “Guide for Concrete Floor and Slab Construction,” provides the following information:
“Reinforcement in nonstructural slab-on-ground installations is provided primarily to control the width of cracks that occur.
… synthetic fibers can help reduce segregation of the concrete mixture and formation of shrinkage cracks while the concrete is in the plastic state and during the first few hours of curing. As the modulus of elasticity of concrete increases with hardening of concrete, however, most synthetic fibers at typical dosage rates recommended by the fiber manufacturers will not provide sufficient restraint to inhibit cracking.”
The Portland Cement Association (PCA) website FAQ section states, in part:
“… Plastic fibers should not be expected to replace wire mesh in a slab on ground. However, although not affecting joint spacing, plastic fibers are used to reduce plastic shrinkage cracking.
For their complete answer, visit http://www.cement.org/tech/faq_fibers.asp.
Plastic shrinkage cracks are those that occur immediately following concrete placement, before the concrete has hardened.”
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Disclaimer: Questions in this column were asked by users of ACI documents and have been answered by ACI staff or by a member or members of ACI technical committees. The answers do not represent the official position of an ACI committee. Only a published committee document represents the formal consensus of the committee and the Institute.