4196.01 DESCRIPTION.
Engineering fabrics, known as geotextiles, shall be permeable, synthetic textile materials suitable for use with soil, rock, or other geotechnical engineering related materials as an integral part of a highway project, structure, or system. They shall be mildew, rot, insect, and rodent resistant and shall be inert to commonly encountered chemicals found in soil. During all periods of shipment and storage, the fabric shall be maintained, wrapped in a heavy duty protective covering to protect the fabric from direct sunlight, ultraviolet rays, mud, dirt, dust, and debris. The fabric shall be free of defects or flaws which significantly effect its physical properties.

Inspection and acceptance of engineering fabrics shall be in accordance with Materials I.M. 496.01. Each roll of fabric in a shipment shall be labeled with a number or symbol to identify the production run. The fabrics shall meet the following additional requirements for the specific applications:

A. Silt Fencing.
Fabric for silt fencing shall be a woven material with a minimum width of 36 inches (0.9 m). The top edge of the fabric shall be hemmed or otherwise modified so that a braided cord or woven belt can be suitably attached for loop tying to fence posts. The cord or belt shall have a minimum tensile strength of 150 pounds (670 N).

The fabric may be reinforced with plastic netting of nominal 3/4 inch (19 mm) strand spacing and a minimum three strand grab strength of 40 pounds (180 N) and 15 pounds (70 N) after the same accelerated weathering as required for the fabric. Fabric that is reinforced in this manner may have lower grab strengths as indicated.

The fabric and any reinforcing plastic netting shall contain or be treated with ultraviolet stabilizers, sufficient to prevent damaging deterioration for 2 years of outdoor exposure. The fabric shall have the following properties:

Property	Value	Test Method
Grab Strength, dry, minimum ave.      full direction      run direction (See Note 1)	100 lbs. (445 N) 150 lbs. (667 N)	Iowa 913 Iowa 913
Grab strength, after      500 hr. in a QUV      weatherometer with a cycle of 4 hr.      UV @ 60°C and 4 hr.      COND @ 40°C,      minimum ave. value in either      principal direction (See Note 1)	50 lbs. (222 N)	Iowa 913
Filtering Efficiency (See Note 2) Flow Time, maximum minutes	25 - 50% 15	Iowa 909 Iowa 909
Note 1. When plastic net reinforcing is used, the minimum average grab strength requirement for fabric, before and after accelerated weathering, shall be 100 pounds (445 N) and 35 pounds (155 N), respectively. The grab strength shall apply to both the fill and run direction. Note 2. Fabrics that do not meet the minimum filtering efficiency requirement may be approved for trial use on specific projects. Approval will be based on acceptable field performance. Fabric exceeding the maximum filtering efficiency will not be considered.

B. Subsurface Drainage.
Fabrics for use in subsurface drains shall be capable of withstanding normal installation stresses and shall have the following properties:

Property	Value	Test Method
Grab strength, dry, minimum ave. value in either principal direction	90 lbs. (400 N)	Iowa 913
Elongation, dry, minimum ave. value in either principal direction	20%	Iowa 913
Water Permeability, K	0.02 - 0.30	Iowa 911
Apparent Opening Size, minimum	40 (450 µm)	Corps of Engineers W-02215

C. Embankment Erosion Control.
Fabric for use under riprap or gabions used for embankment or erosion control shall be capable of withstanding normal installation stresses and shall have the following properties:

Property	Value	Test Method
Grab strength, dry, minimum ave. value in either principal direction	150 lbs. (667 N)	Iowa 913
Elongation, dry, minimum ave. value in either principal direction	20%	Iowa 913
Water Permeability, K	0.02 - 0.30	Iowa 911
Apparent Opening Size, minimum	40 (450 µm)	Corps of Engineers W-02215

D. Asphalt Overlay Fabric.
Fabric placed under asphalt mixtures to provide waterproofing and delay reflective cracking shall be capable of withstanding installation stresses and shall not be damaged by temperatures common to asphalt mixtures. The fabric shall have the following properties:

Property	Value	Test Method
Grab strength, dry, minimum ave. value in either principal direction	90 lbs. (400 N)	Iowa 913
Elongation, dry, minimum ave. value in either principal direction	20%	Iowa 913
Grab Strength after 400°F (204°C) for 3 hr.* minimum ave. value in either principal direction	75 lbs. (335 N)	Iowa 913
*Applies only when asphalt temperatures exceeding 300°F (149°C) are anticipated.

The asphalt absorption shall be sufficient to produce a good bond between the overlay and the overlaid surface when a tack coat of 0.20 gallon to 0.25 gallon (0.9 L to 1.1 L) of asphalt binder per square yard (square meter) is used. Fabrics such as fiberglass, which do not lend themselves to testing by some of the previously specified methods, may be approved by the Engineer.

E. Subgrade Stabilization Material.
Material used to stabilize a subgrade under pavement or pavement patches shall be capable of withstanding installation stresses. The material shall have the following properties for the type specified for use in the contract documents:

1. Polymer Grid. 

Property	Value	Test Method
Minimum tensile strength at 2% strain. Both directions.	250 lbs./ft. (3650 N/m)	Geosynthetic Research Institute (GRI) Test Method GG1-87
Maximum aperture. Both directions.	2 in. (50 mm)	Internal Dimension Measuring Calipers
Minimum aperture. Both directions.	0.5 in. (13 mm)	Internal Dimension Measuring Calipers
Minimum Ultimate junction strength. Both directions.	800 lbs./ft. (11,675 N/m)	GRI Test Method GG2-87

Inspection and acceptance of polymer grid will be in accordance with Materials I.M. 496.01.