Fiber Reinforced Pervious Concrete Specification
May 14, 2014
This Addendum is to be used in conjunction with ACI 522.1 Specification for Pervious Concrete Pavement
ACI 522.2.23 Fibers reads: The use of fibers in pervious concrete is permitted when approved by the Architect/Engineer.
Important: ACI 5188.8.131.52 Opening to Traffic reads: Do not open the pavement to vehicular traffic until the concrete has cured at least 7 uninterrupted days …
Selection and Introduction of Monofilament Microsynthetic Fibers into the Pervious Concrete Mix.
Scope: The intent of this document is to provide an overview of the selection and incorporation of synthetic fibers into the pervious concrete matrix.
It is understood that the pervious concrete pavement is not equivalent to a conventional concrete pavement in design or performance. Although the pervious concrete pavement is a rigid structure it contains a substantial void network and is part of a system for collecting stormwater.
Design: The major components for a successful design of a pervious concrete pavement system can be found in ACI 522.1 Specifications for Pervious Concrete Pavement. This document suggests utilizing the guidelines for developing the appropriate mix design for the standard ingredients, which include the cement, aggregates, water, and admixtures and additives as found in ACI 522.1.
Synthetic Fibers: Including synthetic fibers in the pervious concrete matrix provides a number of benefits to the durability of the pavement. Selecting the appropriate synthetic fiber type and configuration as well as the dosage level and length is critical to the successful use.
The concern with using synthetic fibers is the disruption of the void network within the cross-section of the pavement. Thus it is critical to select the appropriate synthetic fiber and the correct configuration, length and dosage level.
- Select a microsynthetic fiber, not a macrosynthetic fiber.
- Select the configuration. The microsynthetic fiber needs to be a monofilament fiber, not a fibrillated fiber. This requirement may seem obvious, but it is imperative as noted above not to disrupt the void network in the pervious pavement. Use of the fibrillated polypropylene fibers could disrupt the desired void network
- Decide on the length of the monofilament fiber. The maximum length selected should be 3/4″ and the minimum length 1/2″.
- Select the optimum dosage level. The denier or fiber diameter may be a factor in making the decision. The finer the monofilament fiber the more fibers per pound of material. Where the standard denier of the monofilament fiber may be in the 15 denier range the ultra-fine denier is 3 denier or below. Thus there will be a large spread in total fiber count. The suggested starting point is 1.0 to 1.5 pcy for standard denier monofilament fiber and 0.5 to1.0 pcy for ultra-fine denier monofilament fiber. Thus we have taken the fiber count into consideration in selecting the dosage level.
Introduction of Fibers:
Pervious concrete mixes have a very small quantity of mortar (cement and sand). The sand portion is typically limited to less than 3 ft3 per yd3 and commonly held to less than 200 pcy. Therefore, it is important to fabricate some trial mixes to ensure there is sufficient mortar to coat the coarse aggregate and the monofilament fiber. Bear in mind that any changes in the ingredient proportions will have a potential to affect the percentage of voids and the void pattern.
For the monofilament fibers to provide a reinforcement network that will modify cracking, aid in distributing stress, moderate effects of freezing and thawing, and help in supporting the open structure the monofilament fibers must be coated with mortar so that they bond with the concrete matrix.
The last step is selecting the appropriate method required to introduce the monofilament fibers into the pervious concrete mix. To ensure that the fibers distribute uniformly in the pervious concrete mix it is suggested that the monofilament fibers be added in a uniform, consistent manner over a short period of time versus bulk feeding the fibers into the mix.
Monofilament Fiber Specification:
Approved Monofilament Fibers must meet the requirements of ASTM C1116, Section 4.1.3 and Note 2 and must meet the requirements of ICC ES AC32 Sections 3.1.1 and 3.1.2 and possess an ICC ES Engineering Evaluation Report (ESR).
Products Meeting the Above Requirements:
ABC Polymer Industries FiberForce 150TM (Mono-TufTM) (15 denier monofilament polypropylene fiber)
ABC Polymer Industries FiberForce 100TM (Mono-ProTM)(3 denier monofilament polypropylene fiber)
ASTM Test Methods for measuring properties of pervious concrete:
- ASTM C1747 – Determining Potential Resistance to Degradation of Pervious Concrete by Impact and Abrasion
- ASTM C1688 – Density and Void Content of Freshly Mixed Pervious Concrete
- ASTM C1701 – Infiltration Rate of In-place Pervious Concrete
- ASTM C1754 – Density and Void Content of Hardened Pervious Concrete
Bobby Zellers, PE/PLS, Director of Engineering Services, (RZellers@ABCFibers.com)
ABC Polymer Industries, LLC, 545 Elm Street, Helena, AL 35080
Phone: 205.620.9889 Website: www.abcpolymerindustries.com