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By understanding the effects of adding synthetic fibers into pervious concrete mixtures and carefully selecting and introducing the correct fibers into the mix, you can significantly improve the durability of your pervious concrete pavement.

We know there is a major technical advantage in using Fiber Reinforced Concrete versus wire mesh. The quantifiable evidence shows that the 3-dimensional fiber reinforcement is proactive whereas the single layer of wire mesh, at best, is reactive.

Nowhere in ACI's 318 can one find any reference to the substitution of structural steel with microsynthetic or macrosynthetic fibers. Plainly stated when the area of the steel is used in the structural design of the cement concrete-steel composite element then the synthetic fibers cannot replace the steel in question.

ABC Polymer Industries (www.abcpolymerindusties.com) has developed three macrosynthetic fibers, each exhibiting its own well-defined engineering properties in the concrete composite.

Fibril Tuf, a microsynthetic, fibrillated polypropylene fiber, is designed to optimize the mechanical bond between the concrete mortar matrix and the fiber networks.

Fibril Tuf has been tested using the consensus test methods required in ICC ES Acceptance Criteria 32, the single consensus acceptance criteria in the WORLD for evaluating synthetic fibers. Fibril Tuf meets or exceeds all of the AC32 criteria for use as plastic shrinkage crack reinforcement and temperature-shrinkage crack reinforcement.

FRC- Ready Mixer Profit Center

Since Fiber Reinforced Concrete (FRC) is growing in popularity with the engineers and contractors, as well as, referenced within a growing number of project specifications and codes, the Ready Mixer should present and promote the concrete fibers along with the concrete admixtures and additives. Fibers are a Ready Mixer Profit Center!

Why Codes and Specifications Recognize Fibers’ Benefits

With an increasing number of specifications and codes recognizing the use of fibers as plastic shrinkage crack control and temperature-shrinkage crack control reinforcement in concrete rather than wire mesh, the Ready Mixer needs to be able to provide the products required by these specifications and codes.

In those states, counties, municipalities, townships and other smaller governed entities where the ICC International Residential Code is recognized as the controlling building code there has been a modification to the secondary AND the temperature-shrinkage reinforcement specification. The specific reference is IRC Subsection 1909.3 Joints Slabs-on-Ground. herein the code talks to the use of both microsynthetic fibers and wire mesh in residential slabs-on-ground.

It is the building/construction department engineer’s responsibility to select the material that will best meet the needs of the agency in terms of ‘value engineering’ and local conditions. Criteria must be established to ensure that the materials selected provides the end results required.

ICC ES AC32 provides the best acceptance criteria for Microsynthetic Fiber as both secondary/temperature-shrinkage reinforcement and plastic shrinkage cracking reinforcement. Both are addressed in Subsection 1909.3. Additional support documents for the use of Microsynthetic Fibers would include ASTM C1116 and ACI 544.1R.

The use of the wire mesh is also addressed in this subsection. Unfortunately. there is very limited documentation regarding WWF as secondary reinforcement. There are no standard tests to provide limits of performance. All five of the equations used to establish the appropriate WWF to be utilized are empirical equations, which are based solely on observation not performance.

The specifications and the codes recognize the value of FRC versus the use of wire mesh.

The most significant, positive shift in the concrete-value of FRC over wire mesh is ICC’s International Residential Code specifications for residential slabs-on-ground which now explicitly requires that the wire mesh must be supported on permanent supports in the upper half of the slabs. This requirement along with ICC ES acceptance of Fiber Reinforced concrete as reflected in Acceptance Criteria 32, 208 and pending 383 have helped to increase the industries awareness, acceptance, and preference for FRC.

DEPENDABLE

For over 25 years, Fiber Reinforced Concrete (FRC) has delivered solid, dependable results in projects down the street and around the world. Initial acceptance was based more on faith than fact, but conclusive tests now quantify the clear benefits of this 3-dimensional concrete reinforcement system. With the increasing acceptance of FRC came the development of new fibers that contributed even more benefits and value to the concrete.

ABC Polymer Industries now has available a full spectrum of fibers for use in reinforcing concrete. Besides the monofilament and fibrillated polypropylene fibers in multiple forms we also produce macrosynthetic fibers and have available nylon and steel fibers. Also we can provide blends of these various products to meet current specification requirements.

Right now I believe the ready mix producers and the concrete contractors have an excellent opportunity to enhance their financial gains simply by taking the opportunity presented and promote Fiber Reinforced Concrete. The engineering community and the code writers finally have realized there is an advantage to using a 3-dimensional secondary/temperature-shrinkage reinforcement versus a single plane of wire mesh, which more often than not ends up residing on the subgrade.

A: Most ready mixed concrete sales people are not aware of the process required to secure a change order to the specifications for a given project when desiring to replace the wire mesh with FRC or to offer an alternate to the FRC system specified.

Let's Talk about defining industry terms and a little about FRC testing.

There are some terms being used when we are defining synthetic and/or steel fibers as well as their properties and applications that create some confusion for those that may be considering using Fiber Reinforced Concrete.

Plastic Shrinkage Crack Reinforcement would be appropriate for slabs-on-grade and on elevated deck and thin precast concrete elements where the weather conditions (temperature, wind speed and humidity) could produce plastic shrinkage cracks. The cause of plastic shrinkage cracking is rapid loss of moisture from the surface of the concrete element.

Item Microsynthetic Fibers Welded Wire Fabric

1.0 to 1.5 lbs/pcy

6x6 W1.4 x W1.4

6x6 W2.0 x W2.0

There is so much more gained when the engineer specifies synthetic fibers as the  temperature-shrinkage reinforcement instead of the wire mesh. The added value when using the 3-dimensional reinforcement system in lieu of the single plane of wire mesh is truly measurable.

Following A 26.6 percent decline in cement consumption from 2008 to 2009, the Portland Cement Association (PCA) forecasts a modest 5.2 increase in this year-the first year-over-year improvement since consumption peaked in 2005. Stimulus-funded infrastructure projects and pent-up demand for sustainable, cost-effective materials will propel consumption up another 16.5 percent in 2011 and 14.5 Percent in 2012, according to PCA.

It is Spring and the time is ripe to ferret out those projects that are specified with conventional secondary/temperature-shrinkage reinforcement and flip them to current generation microsynthetic fiber reinforcement or new generation macrosynthetic fiber reinforcement.

A: A structurally reinforced slab-on-ground uses a composite of concrete and structural steel to support the design load. Structural steel may be rebar or WWF. The cross sectional area of the steel is inserted into engineering formulae found in ACI 318 to determine the load carrying capacity for a given slab design. In a structural concrete slab the thickness of the slab is not a factor in determining the load carrying capacity of that slab. The cross-sectional area of the steel, spacing of the steel and tensile properties of the steel are the parameters of the steel used in the calculations.

Q: What is the correct placement requirements for WWF in a concrete slab-on-ground?

A: Somewhere in any presentation on Fiber Reinforced Concrete the speaker will show a picture of WWF laying on the subgrade rusting. The speaker will declare that there is no way the laborer charged with the responsibility of elevating the wire mesh to the correct height in the concrete cross-section will ever succeed. The speaker goes on; as long as the laborer is standing on the wire mesh there is no way it will ever be raised to the correct height.

Engineering Report

Impact Resistance – There is a test described in ACI 544.2 which uses a modified Proctor Density/Marshall Compaction set-up. A 10 pound hammer dropped 18’’ inches imparts a dynamic load on a steel ball that transfers the load to a concrete disk. This test has been used to show how the 3-dimensional network of fibers distributes this point load to a greater mass of the concrete. The cracking pattern of the fiber reinforced concrete disks are visually different than those of the plain concrete tested. Furthermore, this test shows how the fibers hold the concrete together after it cracks. Anyone who has tried to jack-hammer FRC can attest to its impact resistance.

Microsynthetic Fibers:

Microsynthetic Fibers are the original generation of synthetic fiber and are comprised of polypropylene monofilament and fibrillated fibers and nylon monofilament fibers. Typically these fibers are ¾” (19mm) long and are used at a dosage rate of 1 to 1.5 pounds per cubic yard as a means to address plastic shrinkage reinforcement and/or secondary/temperature-shrinkage reinforcement. The length range for microsynthetic fibers is ¼” to 2 ½” and the dosage range is 0.5 to 3.0 pcy.