ISO Standard Values Relevant to Biaxial Woven Polyester Geogrids
ISO 10319:2015 outlines the procedure for testing the tensile strength and elongation of geogrids, which is critical for biaxial woven polyester geogrids. Below are key parameters relevant to Biaxial Geogrid:
- Tensile Strength: Measured in kN/m, this is the maximum force per unit width that the geogrid can withstand before breaking. For biaxial geogrids, tensile strength is tested in both longitudinal (machine direction, MD) and transverse (cross-machine direction, TD) directions.
- Elongation at Break: Expressed as a percentage, this indicates the strain at which the geogrid fails under tensile load. Typical values for polyester geogrids are in the range of 10–13%, as noted in your provided data and supported by web sources.
- Tensile Strength at Specific Strains: ISO 10319:2015 allows for measuring tensile strength at specific strain levels (e.g., 2% or 5%), which is useful for comparing geogrid performance under operational conditions.
- Junction Efficiency: While not directly specified in ISO 10319:2015, junction efficiency (typically 90–95% for woven polyester geogrids) can be evaluated through related standards like ASTM D7737-11, which measures load transfer capability at junctions.
- Test Conditions: ISO 10319:2015 requires testing under controlled conditions (e.g., 20°C ± 2°C, 65% ± 5% relative humidity) using a wide-width strip (typically 200 mm wide) to ensure accurate representation of in-field performance.
Additional standards that may apply include:
- ASTM D6637-15: Used for determining tensile strength of geogrids, often referenced alongside ISO 10319:2015 for biaxial geogrids.
- JC893.1-1998 & JT/T480-2002: Chinese standards cited for polyester geogrids, specifying tensile strength and elongation properties.
- ASTM D7748-14: Measures resistance to bending forces, relevant for assessing geogrid stability in applications.
Based on your provided data and web sources, biaxial woven polyester geogrids typically have:
- Material: High-tenacity polyester yarns, often coated with PVC, bitumen, or SBR for UV and chemical resistance.
- Elongation: 10–13% at break, with some sources indicating ≤4% for specific products.
- Mesh Size: Common sizes range from 12.7 x 12.7 mm to 40 x 40 mm, allowing interaction with fill material.
- Applications: Retaining walls, road bases, embankments, and slope stabilization.
Comparison Chart for Biaxial Woven Polyester Geogrids
The chart below compares biaxial woven polyester geogrids with minimum tensile strengths of 20 kN/m, 40 kN/m, and 60 kN/m in both longitudinal and transverse directions.
| UTS (kN/m) | Material | Tensile Strength @ 2% Strain (kN/m) | Tensile Strength @ 5% Strain (kN/m) | Elongation at Break (%) | Junction Efficiency (%) | Polymer Type | Typical Applications | ISO Test Standard |
|---|---|---|---|---|---|---|---|---|
| 20/20 | PET | 4–6 | 8–12 | 10–13 | 90–95 | Biaxial | Retaining walls, road base | ISO 10319:2015 |
| 40/40 | PET | 8–12 | 16–24 | 10–13 | 90–95 | Biaxial | Embankments, pavements | ISO 10319:2015 |
| 60/60 | PET | 12–18 | 24–36 | 10–13 | 90–95 | Biaxial | Heavy pavements, slopes | ISO 10319:2015 |
Notes on the Comparison:
- UTS (kN/m): The tensile strength values (20/20, 40/40, 60/60 kN/m) are specified for both longitudinal and transverse directions, as is standard for biaxial geogrids. These align with typical biaxial polyester geogrid specifications.
- Tensile Strength at 2% and 5% Strain: Estimated based on proportional scaling from your uniaxial data (e.g., 20–30 kN/m at 2% strain for 100 kN/m UTS). For biaxial geogrids, these values are typically lower than uniaxial due to balanced strength distribution. Exact values depend on manufacturer specifications, but ranges are consistent with industry norms.
- Elongation at Break: Set at 10–13%, as per your data and confirmed by sources for polyester geogrids. Some sources suggest ≤4% for specific products, but 10–13% is more typical for woven polyester.
- Junction Efficiency: Assumed at 90–95%, consistent with your data and typical for woven polyester geogrids with stable junctions.
- Polymer Type: Specified as biaxial to reflect the bidirectional strength requirement.
- Applications: Adjusted to reflect common uses for biaxial geogrids, such as pavements and embankments, which benefit from equal strength in both directions.
- ISO Test Standard: ISO 10319:2015 is the primary standard for tensile testing, as specified in your data and widely used for polyester geogrids.
Additional Considerations:
- Coating: Biaxial woven polyester geogrids are often coated with PVC, bitumen, or SBR to enhance UV resistance, durability, and adhesion (e.g., in asphalt reinforcement).
- Mesh Size: Typically 12.7–40 mm, allowing effective soil interlock.
- Testing Notes: ISO 10319:2015 involves wide-width tensile testing, which is critical for biaxial geogrids to ensure uniform stress distribution. Manufacturers may also report values per ASTM D6637-15 for U.S. markets.