738GEOGRIDS

738.1POLYMER REQUIREMENTS—

Geogrids must be manufactured from either polymeric coated polyester (PET), high density polyethylene (HDPE), or polypropylene (PP) polymer according to the class and type indicated. No post -consumer recycled material is allowed in polymer resins used in the manufacturing of geogrid products. Requirements for the polymers are indicated in Table A.

Table A1 Requirements for Geogrid Polymers (All values are minimums unless indicated otherwise) Property Units Test Method PET HDPE PP Carboxyl End Group (CEG) Content of PET Yarns mmol/ kg ASTM D7409 < 30.0 N/A N/A Number Average Molecular Weight (Mn) of PET Yarns - ASTM D4603 25,000 N/A N/A Polymeric Coating Except for manufacturing selvedge edges, the polymeric coating for PET geogrids must be continuous with no more than 10% of the surface area having uncoated, unbound fiber bundles as determined according to ASTM D610 , 5.1 -5.3 and

5.5Procedure.4

N/A N/A Carbon Black Content2 % ASTM D5596, ASTM D1603 or ASTM D4218 N/A 1.0 to 3.5 1.0 to 3.5 Melt Flow Index g/10 min ASTM D1238 using Condition 190/2.16 for HDPE and Condition 230/2.16 for PP N/A 0.50 0.25 Density g/cm3 ASTM D792 or ASTM D1505 N/A 0.940 0.905 Resistance to UV Degradation3 % ASTM D4355 and ASTM D6637 (Method A or B) N/A 95 95 Notes:

maximum average roll value and Carbon Black Content which is a minimum and maximum average roll value range. The maximum average roll values are determined mathematically similar to a MARV, except the values are the average plus two standard deviations.

tested to determine the Ultimate Tensile Strength (T U) in the machine direction (MD) for uniaxial geogrids and both the machine and cross machine directions (MD and XD) for biaxial geogrids. The value is calculated by dividing T U of the UV exposed material by the T U of the virgin material and multiplying by 100. TU of all samples are determined according to ASTM D6637, Method B. For biaxial geogrids the minimum required value must be met in both the MD and XD.

or unbound surface area.

738.2CLASS 1 UNIAXIAL GEOGRIDS—

stabilized earth (MSE) walls.

longitudinal and transverse polymer tensile elements having aperture geometry sufficient to permit

mechanical interlock with the surrounding material. Required values and test methods for geogrid properties are indicated in Table B. Sample materials according to ASTM D4354.

Table B Requirements for Class 1 Geogrids – Uniaxial Geogrid Reinforcement (All values are minimums unless indicated otherwise) Design Parameter Units Test Method Type A Type B Polymer Type - N/A Polymeric Coated PET Integrally Formed5 HDPE Ultimate Tensile Strength, (TU) lbs/ft ASTM D6637 (Method B) Design Specific Creep Reduction Factor, (RFCR)1 (determined for a 100 year design life) - AASHTO R 69, ASTM D5262, and ASTM D6992 1.60 2.60 Installation Damage Reduction Factor, (RFID)1,2 - AASHTO R 69 1.30 1.30 Durability Reduction Factor, (RFD)1 - N/A 1.20 1.10 Combined Reduction Factor (RFOV)1,3 - AASHTO R 69 2.50 3.70 Machine Direction (MD) Aperture Size in. N/A 0.60 to 6.0 (Min. to Max.) 0.60 Cross Machine Direction (XD) Aperture Size in. N/A 0.50 0.50 Rib Section Area Ratio4 - N/A 0.30 0.30 Percent Open Area % N/A 45 45 Notes:

Tensile Strength. If product specific data values are lower, the value indicated in Table B must be used. If product specific data values are higher, the product specific data values must be used.

1.5 inch as specified in Section 738.2(b)3.

MARV is determined by subtracting two standard deviations from the average ultimate tensile strength obtained from the last twelve months of manufacturer quality control testing. Conduct testing for T U according to ASTM D6637, Method B.

to AASHTO R 69, ASTM D5262, and ASTM D6992. Test samples unconfined in the direction in which the load will be applied. Use the ratio of ultimate strength to creep limiting strength to c alculate the creep reduction factor. If the calculated creep reduction factor is greater than the creep reduction factor indicated in Table B, use the calculated creep reduction factor.

factor (RFID) indicated in Table B for material with a maximum particle size of 1.5 inches (excluding random oversized particle sizes) unless project specific conditions or a specific geogrid indicates a higher value that was determined according to AASHTO R 69. For materials having greater than 1.5-inch maximum particle size, determine RFID according to AASHTO R 69 except as follows:

RFID = TU/Tdam RFID must never be less than 1.3.

indicated in Table B unless project specific conditions or a specific geogrid indicates a higher value.

geogrid using the individual reduction factors to account for installation damage, durability, and creep. The Combined Reduction Factor is the product of the individual reduction factors. Maximum allowable strain of the geogrid is 5 percent for the 100-year design life when applying the Combined Reduction Factor (RFov). Determine the allowable long-term geogrid strength (TL) from:

TL = TU / RFOV, or T5, whichever is less RFOV = RFCR x RFID x RFD TL ≥ Td

where:

TL = long-term allowable geogrid tensile strength (lbs/ft). TU = ultimate tensile strength (lbs/ft). RFOV = combined reduction factor (dimensionless). RFCR = creep reduction factor (dimensionless). Ratio of TU to creep-limiting strength, determined according to AASHTO R 69. Use the minimum value indicated in Table B, unless product specific values are greater, use the higher product specific value. RFID = installation damage reduction factor (dimensionless). Use the minimum value indicated in Table B. If product specific value is higher, use the product specific value. RFD = durability reduction factor (dimensionless). Use the minimum value indicated in Table B, unless project specific conditions or specific geogrid indicate a higher value. Td = required design tensile strength of geogrid reinforcement (lbs/ft). T5 = MARV tensile strength at 5 percent elongation (lbs/ft).

738.3CLASS 2 BIAXIAL GEOGRIDS—

or similar applications. Polypropylene (PP) biaxial grids are required for stabilization (confinement) applications. Polyester (PET) geogrids are required for reinforcement applications such as load distribution pads or slope reinforcement.

longitudinal and transverse polymer tensile elements having aperture geometry sufficient to allow mechanical interlock with the surrounding material. Provide Class 2 , Type A and B biaxial geogrids fabricated of stiff ribs with connections that are either integrally formed or welded. Provide biaxial geogrid conforming to the properties indicated in Table C. Sample materials according to ASTM D4354.

Table C Required Properties for Class 2 Biaxial Geogrids (All values are minimums unless indicated otherwise) Property Units Test Method Type A Type B Type C Subgrade and Subbase Stabilization Reinforcement Polymer Type – - PP PP Polymeric Coated PET Aperture Size1,2 in - 1.0 to 1.7 (Min. to Max.) 1.0 to 1.7 (Min. to Max.) N/A Aperture Open Area3 in2 - 1.0 to 2.9 (Min. to Max.) 1.0 to 2.9 (Min. to Max.) N/A Percent Open Area % - 65 65 65 Ultimate Tensile Strength, (TU)1,4 lbs/ft ASTM D6637 (Method B) 1,080 1,780 Design Specific Elongation at Ultimate Tensile Strength1 % ASTM D6637 5.0 to 15.0 (Min. to Max.) 5.0 to 15.0 (Min. to Max.) N/A Junction Efficiency5 % ASTM D7737 and ASTM D6637 90 90 N/A Flexural Rigidity g-cm ASTM D1388 >1,000 >1,000 N/A Resistance to Installation Damage6 % AASHTO R 69 80 80 N/A Notes:

geogrids are as specified in Table C. TL for Class 2, Type C biaxial geogrids is determined as specified in Section 738.2(b)5 for Class 1, Type A uniaxial geogrids, with TU not less than 2,000 lb/ft in either the MD or XD direction. Do not apply reduction factors to Class 2, Type A and B biaxial geogrids.

738.4HANDLING and STORAGE—At a minimum, conform to ASTM D4873 for identification, storage ,

and handling of geogrid . Provide clear identification to every roll of geogrid that provides identification of product designation, the manufacturer’s name, lot number, material quantity, and clearly differentiates between rolls of similar geogrid. P rotect the geogrid from direct sunlight, ultra-violet rays, temperature greater than 140F, mud, dirt, dust, and debris.

738.5CERTIFICATION—Certify each shipment as specified in Section 106.03(b)3. Verify that the product

received meets the designed value for TU as specified on the plans . If verification testing is performed, testing must be conducted according to the standards and procedures indicated herein for the material Class and Type. When conducting verification testing for tensile strength, follow ASTM D6637 (Method B), except the calculated tensile stre ngth is determined using the average value of the test results for a minimum of ten test specimens. The calculated tensile strength must be greater than TU listed in Bulletin 15.

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