106 SECTION 206 BASE COURSE REINFORCEMENT GEOGRID
206.1 -DESCRIPTION : This work shall consist of furnishing, testing and installing base reinforcement geogrid elements in accordance with these specifications and in reasonable close conformity with the lines, grades and dimensions shown on the plans or established by the Engineer. Design details for base reinforcement geogrid such as geogrid type, base aggregate minimum thickness, asphalt thickn ess and associated details shall be shown on the plans.
206.2 -REFERENCE DOCUMENTS : ASTM Standards: D1388 Flexural Rigidity D4355 Practice of Sampling of Geosynthetics for Testing D4595 Test Method of Tensile Properties of Geotextiles by the Wide Width Strip Method Corps of Engineers: COE CW02215 Percent open area Geosynthetic Research Institute: GG1 Standard Test Method for Geogrid Rib Tensile Strength GG2 Standard Test Method for Geogrid Junction Strength
206.3 -GEOGRID MATERIAL : 206.3.1 -General : The Contractor shall be responsible for obtaining the geogrid reinforcement materials and associated components that meet all requirements of the Specification. Geogrid reinforcement elements shall consist of a regular network of integrally connected longitudinal and transverse polymer tensile elements with aperture geometry suf ficient to permit significant mechanical interlock with the surrounding soil, aggregate or other material.
206.3.2 -Certification of Materials and Submittals: 206.3.2.1 -Specification Compliance Certification: Prior to construction the Contractor shall submit to the Engineer the Manufacturer’s certification that the geogrid has been evaluated in full compliance with this Specification. The Contractor’s submittal package shall include; but not be limited to; the Manufacturer's written certification that all resin used to produce the geogrid is virgin and classified as polypropylene or high molecular weight polyester.
206.3.2.2-Fitness for Use: The Manufacturer of the base reinforcement geogrid shall supply written certification that the resin and add itives used in manufacture of the geogrid (including coating materials, if applicable) and that the Manufactured geogrid product has been evaluated in accordance with this specification and is durable in a soil environment. Certification shall be notarize d and signed by an officer of the manufacturing company.
107 206.3.3 -Base Course Reinforcement Geogrid: The geogrid shall be a biaxial geogrid and shall have aperture geometry and rib and junction cross -sections sufficient to permit significant mechanical interlock with the material being reinforced. The geogrid shall have high flexural rigidity and high tensile strength at ribs and junctions of the grid structure. The geogrid shall maintain its reinforcement and interlock capabilities under repeated dynami c loads while in service and shall also be resistant to ultraviolet degradation, to damage under normal construction practices, and to all forms of biological or chemical degradation normally encountered in the material being reinforced. The geogrid shal l also conform in all respects to the property requirements outlined below:
PROPERTY TEST METHOD UNITS TYPE I TYPE 2 Interlock Aperture Size 1 I.D. Calipered 2 MD in 1.0 (nom) 1.0 (nom) CMD in 1.3 (nom) 1.3 (nom Open Area COE Methold 3 % 70 (min) 70 (min) Thickness ASTM D1777 Ribs in 0.03 (nom) 0.05 (nom) Junctions in 0.11 (nom) 0.16 (nom) Secant Aperture Stabil ity Modulus @ 20 cm-kg Grid Aperture Test Univ. of Alaska , Fairbanks 4 cm-kg/deg 3.2 6.5 Reinforcement Flexural Rigidity ASTM D1388 5 mg-cm 250,000 (min) 750,000 (min) True Initial Modulus GRI GG1 -87 6 lb/ft 15,000 (min) 32,000 (min) Tensile Strength @ 2% strain ASTM D4595 7 1b/ft 280 (min) 410 (min) Tensile Strength @ 5% strain ASTM D4595 7 1b/ft 580 (min) 810 (min) Junction Strength GRI GG2 -87 8 lb/ft 765 (min) 1080 (min)
*All values listed are RV’s (Minimum Average Roll Values .) Notes:
CW 02215 Civil Works Construction Guide, November 1977.
deforming test materials under load before measuring such resistance or employing “secant” or “offset” tangent methods of measurement so as to overstate tensile properties.
materials under load before measuring their tensile strength so as to overstate tensile properties.
“Geogrid Junction Strength”.
108 206.3.4 -Alternate Material: Alternate geogrid materials will be considered . However, the material properties of the geogrid must be evaluated based on testing the total structure and not based on simply adding the values of the individual components/layers together. Also, no preloading or strain “offset” is permitted when repo rting True Initial Modulus values as outlined in the table found in section 3.3 Base Course Reinforcement Geogrid. Such materials must be pre -approved in writing by the Engineer prior to bid date. Alternate material packages must be submitted to the Engi neer a minimum of 15 days prior to bid date. Submittal packages must include the following as a minimum:
with the specific geogrid which quantifies the structural contri bution of the geogrid to the pavement structure. The increase in the structural layer coefficient of the base course must meet or exceed that of the design geogrid.
stability modulus at 20 cm -kg, when tested in accordance with the “Grid Aperture Stability by In -Plane Rotation” test of 3.2 or greater for Type 1 and 6.5 or greater for Type 2.
States, where the results of the specific alternate geogrid’s use can be verified after a minimum of one year of service life.
The burden of proof that the alternate material is equal to the specified material is the responsibility of the alternate geogrid material supplier. The Engineer will be the sole judge of the adequacy of the proposed alternate geogrid.
206.4 -MANUFACTURING QUALITY CONTROL : Conformance testing shall be performed as part of the manufacturing process. If the Manufacturer has an established quality control program, then documentation d escribing the program shall be submitted to the Engineer for review. As a minimum, the Manufacturer shall conduct quality control testing as outlined below:
Test Test Procedure Testing Frequency (SF) Flexural Rigidity ASTM D1388 100,000 Tensile Modulus GRI GG1 100,000 Junction Strength GRI GG2 100,000
The Manufacturer shall perform these tests. Samples not satisfying the specifications shall result in the rejection of the applicable rolls at no cost to the owner. At the Manufacturer’s discretion and expense, additional testing of individual rolls may be performed to more closely identify the noncomplying rolls and/or to qualify individual rolls. The Manufacturer shall certify the quality of the rolls of geosynthetic rein forcement. As a minimum, the Manufacturer shall provide quality control certificates for each batch of resin and each shift’s production. These quality control certificates shall be signed by an office of the Manufacturer and supplied to the Engineer at least fourteen (14) days prior to installation of the base reinforcement geogrid.
109 The quality control certificate shall include:
206.5 -TRANSPORTATION, HANDLING AND STORAGE : The Contractor shall check the geogrid upon delivery to ensure that the proper material has been received. Duringal l periods of shipment and storage, the geogrid shall be protected from temperatures greater than 140º F and all deleterious materials that might otherwise become affixed to the geogrid and adversely affect its performance. Follow Manufacturer’s recommendations in regards to protection from direct sunlight. All tears, cracks, punctures or flaws to the base reinforcement geogrid coating, if applicable, shall be repaired by placing a suitable patch over the defective area as approved by the Engineer. If the substrate of a coated geogrid is exposed at roll ends or as a result of cuts, cracks, punctures or flaws, the exposed area shall be sealed with a coating solution identical to the original coating. The coating solution shall be applied by dip coating or spread coating with an applicator. The area shall be thoroughly clean and dry, and working temperatures shall not be below 32°F. All exposed substrate or repair patches shall be treated in the same manner.
206.6 -CONSTRUCTION : A qualified and experienced representative of the geogrid manufacturer or its supplier shall be on site, for a minimum of one day at the start of installation, to assist the Contractor and the Engineer in the proper construction/installation techniques. Thereafter, the representative shall be available on an a s needed basis, as requested by the Engineer, during the construction of the remainder of the project. A quality assurance program shal l be conducted by the owner’s representative verifying that the product supplied to the jobsite meets the design requirements. Independent testing of field samples shall be conducted at the frequencies outlined below.
Property Method Frequency (S Y) Flexural Rigidity ASTM D1388 150,000 Tensile GR1 GG1 150,000 Junction Strength GR1 GG2 150,000
Foundation soil shall be excavated to the lines and grades as shown on the drawings or as directed by the Engineer. Geogrid shall be laid at the proper elevation and orientation as shown on the construction drawing or as directed by the Engineer. Correct orientation (roll direction) of the geogrid shall be verified by the Contractor. Geogrid may be temporarily secured in -place with staples, pins, sand bags or backfill as required by fill properties, fill placement procedures, or weather conditions, or as directed by the Engineer. Base course aggregate material shall be placed in lifts and compacted as directed under minimizes the development of wrinkles in and/or movement of the geogrid. Tracked construction equipment shall not be operated directly upon the geogrid. A minimum fill thickness of four ( 4) inches is required prior to operation of tracked vehicles over the geogrid. Turning of tracked vehicles should be kept to a minimum to prevent tracks from displacing the fill and damaging the geogrid. Rubber tired equipment may pass over the geogrid re inforcement at slow speeds, less