synthetic fibers for Concrete




Micro fibers are used to control plastic shrinkage cracks in concrete and improve slip form concrete placements, such as barrier rail. Macro fibers control cracking in hardened concrete, add toughness, and impact and fatigue resistance to hardened concrete.




Acceptance of synthetic fibers for concrete for use on Iowa Department of Transportation projects will be on the basis of manufacturer and brand name approval. Approved manufacturers and brands of synthetic fibers are listed in the Materials Approved Products Listing Enterprise (MAPLE) as Appendixes A and B for two types of applications. Appendix A lists the approved fibrillated fibers and the Appendix B lists approved macro structural fibers.


The manufacturer shall submit the following items to the Engineer:


1.    Product identification including brand name and product number

2.    A set of current product literature and complete manufacturer recommendations for usage

3.    Current Material Safety Data Sheet (MSDS).


Micro fibers shall meet the requirements of ASTM C1116, Type III. Fibers shall be 100% virgin polypropylene, fibrillated, rough textured, interconnected fibers containing no reprocessed olefin materials.


Macro polyolefin fibers shall meet the requirements of ASTM C1116 and ASTM D7508 with the following exceptions:


         Cut length shall be 1.25 to 2.5 inches

         Aspect Ratio shall be a maximum of 150


In addition, when macro fiber-reinforced concrete is specified for a PCC pavement overlay, macro polyolefin fibers shall be used at an addition of 5.0 pounds per cubic yard evenly distributed into the mix. If less than 5.0 lbs. per cubic yard of macro polyolefin fiber reinforcement is used in the mix, the Contractor shall provide test results showing the mix design has a residual strength of 150 psi as determined by ASTM C1609. Mixing shall be as recommended by the manufacturer such that the fibers do not ball up.



The manufacturer shall file a certification at the beginning of each calendar year stating that the material supplied during that year is identical to material previously tested and approved by the Construction and Materials Bureau.



The Construction and Materials Bureau may sample and test synthetic fibers at any time to verify compliance with specification requirements.