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In 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 about 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 provide 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.

1. Temperature-Shrinkage Reinforcement:

Here is verbiage was taken directly from the code.

Concrete slabs on ground containing Microsynthetic fiber reinforcement. Fiber length shall be a ½ inch to 2 inches (13 to 51 mm) in length. [Typically specified length sha¾” (19 mm)]. Dosage amounts shall be from 1.0 to 1.5 pounds per cubic yard (0.6 to 0.9 kg/cubic meter) in accordance with the manufacturer’s recommendations. The Microsynthetic fibers shall comply with ASTM C1116, Section 4.1.3 and Note 3 and ICC ES AC32, Sections 3.1.1 and 3.1.2. The manufacturer or supplier shall provide certification of compliance with ASTM C1116 and ICC ES AC32 when requested by the building official. Dosage rate shall be established per the manufacturer’s recommendations in compliance with the minimum requirement of the agency.

Concrete slabs on ground containing 6×6 W1.4 x W1.4 welded wire reinforcement fabric located in the middle to the upper 1/3 of the slab. Welded wire reinforcement fabric shall be supported with approved materials or supports at spacing not to exceed 3 ft (914 mm) in both the North-South and East-West directions or in accordance with the manufacturer’s specifications. Welded plain wire reinforcement fabric for concrete shall conform to ASTM A185, Standard Specification for Steel Welded Wire Reinforcement, Plain for Concrete Reinforcement.

Fibers a Viable Option for Temperature –Shrinkage Reinforcement:

The above proposed added verbiage to the code provides for an option to conventional temperature-shrinkage reinforcement with the use of microsynthetic fibers and, in addition, mandates that the conventional welded wire reinforcement fabric is properly placed in the concrete cross-section to ensure optimum performance, which is not currently achieved in most cases.

In the case of sidewalks that are within the boundaries of the ingress and egress of private, commercial and industrial establishments and in areas where the concrete slabs-on-ground are subject to more than foot traffic the Microsynthetic fibers will provide increased fatigue strength, impact resistance and surface abrasion resistance.

Financial Impact of Proposed Amendment:

What should result from providing this new verbiage is a more durable, longer performing concrete slab on ground. Thus the repair and/or replacement cycle will be extended resulting in a much-improved life cycle cost.

Providing an alternative secondary reinforcement materials’ language enables the government agency to also benefit from reduced initial in- place costs when using the Microsynthetic fiber based on the current pricing of wire mesh.

2. Plastic Shrinkage Reinforcement

Here is verbiage was taken directly from the code.

As an alternative to secondary/temperature-shrinkage reinforcement provided by microsynthetic fibers, there is plastic shrinkage reinforcement, which provides to a lesser degree enhancement to the concrete durability. Concrete slabs on ground containing Microsynthetic fiber reinforcement. Fiber length shall be 1/2 inch to 2 inches (13 to 51mm) in length. [Typical specified length shall be a ¾ inch (19mm)]. The Microsynthetic fibers shall conform with ASTM C1116, Section 4.1.3 and Note 3 and ICC ES AC32, Section 3.1.1. The manufacturer or supplier shall provide certification of compliance with ASTM C1116 and ICC ES AC32 when requested by the building officials. Dosage rate shall be established per the manufacturer’s recommendations in compliance with the minimum requirement of the agency.

No welded wire reinforcement fabric will be specified for Plastic Shrinkage Reinforcement.

Fibers a Viable Option for Plastic-Shrinkage Reinforcement

The proposed verbiage for Plastic Shrinkage Reinforcement provides the specifying agency the option to include a uniquely applicable reinforcement to the concrete solely to mitigate the potential negative effects of plastic shrinkage cracking and plastic settlement. This reinforcement system will perform within the first 12 hours of the concrete’s life.

Financial Impact of Proposed Amendment:

What should result from this proposed verbiage is:

• A more uniform concrete, thus a more durable concrete.
• Fewer potential flaws caused by ambient conditions (wind, temperature, and humidity) when the concrete is placed resulting in longer effective service with less maintenance.

Prepared by R.C. Zellers, PE/LS, Director, Engineering Services, ABC Polymer Industries, LLC