How to Read Geomembrane GRI-GM13 Specifications | Density, Carbon Black, OIT, and Stress Crack Resistance

Purchasers and project engineers still need to confirm the applicable GRI-GM13 revision, geomembrane surface type, nominal thickness, test method, reported unit, acceptance value, testing frequency, and traceability of the submitted results.

Density, carbon black content, carbon black dispersion, oxidative induction time, and stress crack resistance are particularly important because they provide information about the formulation and long-term durability characteristics of an HDPE geomembrane. They are also frequently misunderstood.

A density result does not independently prove chemical compatibility. Carbon black content does not show whether the carbon black is properly dispersed. A high OIT value does not directly predict service life. A 500-hour stress crack result does not mean the liner will last only 500 hours.

This guide explains how to interpret these properties correctly and how to identify incomplete or misleading geomembrane test reports.

What GRI-GM13 Covers

GRI-GM13 Applies to Smooth and Textured HDPE Geomembranes

GRI-GM13 is published by the Geosynthetic Research Institute and is titled “Test Methods, Test Properties and Testing Frequency for High Density Polyethylene Smooth and Textured Geomembranes.”

The current Revision 19, dated June 11, 2025, covers smooth and textured HDPE geomembranes with a formulated sheet density of at least 0.940 g/cc and nominal thicknesses from 0.75 mm to 3.0 mm, equivalent to approximately 30 to 120 mil.^[1]

Separate property tables are used for smooth and textured geomembranes. Buyers should not apply smooth-sheet tensile, elongation, thickness, or puncture values directly to a textured product.

The first step in reviewing a submission is therefore to confirm:

• The material is HDPE rather than LLDPE, fPP, PVC, or another polymer.
• The stated surface is smooth, single-textured, or double-textured.
• The nominal thickness matches the project specification.
• The supplier is referencing the correct GM13 revision.
• The reported results correspond to the actual product being offered.

LLDPE geomembranes are normally reviewed under the applicable GRI-GM17 specification rather than being treated as a flexible variation of GM13 HDPE.

Further information: Jinseed HDPE Geomembrane Liner and Jinseed Textured Geomembrane.

GRI-GM13 Is Primarily a Manufacturing Quality-Control Specification

GRI-GM13 identifies minimum physical, mechanical, chemical, and endurance properties, together with minimum manufacturing quality-control testing frequencies.

It does not provide a complete project design. It does not determine:

• The correct geomembrane thickness for a specific site.
• The required liner-system configuration.
• Site-specific chemical compatibility.
• Interface shear strength for a particular slope.
• Required protection geotextile.
• Allowable strain caused by settlement.
• Installation procedures and weather limitations.
• The complete construction quality-assurance plan.
• A guaranteed geomembrane service life.

A project specification may adopt GRI-GM13 and then add more restrictive requirements, additional tests, higher acceptance values, or application-specific compatibility testing.

Important distinction: Meeting GRI-GM13 means the tested product satisfies the stated manufacturing specification. It does not independently prove that the material is suitable for every containment application.

The Current Revision Also Includes HDPE Seam Requirements

Revision 19 added HDPE seam specifications in an appendix in place of the former reliance on GRI-GM19 for this material category.^[1]

However, sheet-property compliance and field-seam compliance remain separate review tasks.

A roll can meet the GM13 sheet requirements while field seams fail because of:

• Incorrect welding temperature.
• Unsuitable welding speed or pressure.
• Moisture, dust, or contamination in the overlap.
• Insufficient surface preparation.
• Unsupported wrinkles.
• Incorrect extrusion-welding procedure.
• Changing weather conditions.

The material certificate should therefore not be used as a replacement for trial seams, nondestructive testing, destructive peel and shear testing, and field repair records.

How to Read a GRI-GM13 Property Table

Read Each Row from Left to Right

A GRI-GM13 property table contains several types of information. A correct review should follow the entire row rather than looking only at the reported result.

Do Not Treat Every Value as a MARV

GRI-GM13 specifically states that the numerical values in its tables are neither minimum average roll values nor maximum average roll values. They must be interpreted according to the stated test method.^[1]

This distinction matters because the acceptance basis varies by property.

Examples include:

• A minimum value, such as formulated sheet density.
• A specified range, such as carbon black content.
• A minimum average, such as certain mechanical properties.
• A lowest individual measurement requirement, such as thickness control.
• A retained percentage after aging.
• A qualitative category result, such as carbon black dispersion.
• A minimum failure time, such as stress crack resistance.

A report should not label all GM13 limits as “MARV” merely because that term is commonly used on other geosynthetic data sheets.

Separate Specification Values from Actual Results

A common supplier data sheet contains only the GM13 limit and the word “pass.” That may be acceptable as a basic product declaration, but it is not the same as a batch-specific manufacturing quality-control report.

For project acceptance, request actual test values connected to the relevant production batch, resin formulation, and roll numbers.

How to Read Geomembrane Density

The GM13 Requirement Applies to the Formulated Sheet

GRI-GM13 requires a minimum formulated HDPE geomembrane sheet density of 0.940 g/cc. Density may be measured using ASTM D1505 or ASTM D792, with Method B recommended when ASTM D792 is used.^[1]

The phrase formulated sheet density is important. It refers to the finished geomembrane formulation, which includes the polyethylene resin and incorporated additives.

It should not automatically be interpreted as the density of the unformulated base resin.

ASTM D792 determines density and relative density of solid plastics by displacement. It includes procedures using water or another appropriate liquid.^[2]

Higher Density Is Not Automatically Better

A result of 0.947 g/cc is not automatically superior to a result of 0.942 g/cc.

Density is influenced by:

• Base resin structure.
• Polymer crystallinity.
• Carbon black content.
• Additives and stabilizers.
• Fillers or unintended contamination.
• Manufacturing and cooling history.

A higher density result cannot independently prove:

• Higher puncture resistance.
• Better stress crack resistance.
• Better weldability.
• Longer service life.
• Higher chemical compatibility.
• Use of virgin resin.
• Absence of mineral filler.

Density should be reviewed with carbon black, ash or compositional information where required, tensile properties, stress crack resistance, OIT, and manufacturing traceability.

Incorrect interpretation: “The density is high, so every other performance property must also be high.”

Correct interpretation: “The formulated sheet meets the GM13 density classification, but the remaining properties must still be evaluated separately.”

How to Review a Density Test Result

A complete density entry should identify:

• Actual measured density.
• Unit, normally g/cc or g/cm³.
• ASTM D1505 or ASTM D792.
• Applicable method where relevant.
• Sample identification.
• Production batch or lot.
• Test date.
• Required acceptance value.

How to Read Carbon Black Content and Dispersion

Carbon Black Content and Dispersion Are Different Tests

Carbon black is incorporated into black polyethylene geomembranes to improve resistance to ultraviolet-induced degradation. However, carbon black performance depends on both the amount present and how well it is dispersed through the polymer.

GRI-GM13 treats these as two separate properties:

A product can contain 2.5% carbon black and still have poor dispersion. Conversely, a visually uniform microscopic sample cannot compensate for carbon black content outside the specified range.

Carbon Black Content Must Be Within a Range

GRI-GM13 specifies carbon black content between 2.0% and 3.0% by mass.^[1]

This is a range rather than a simple minimum.

More carbon black should not automatically be considered better. Excessive carbon black or an incorrect formulation can affect processing, mechanical behavior, dispersion, and consistency.

ASTM D4218 is used to determine carbon black content in applicable black polyethylene compounds by a muffle-furnace technique. ASTM describes it as suitable for manufacturing quality control, technical service, and research work.^[3]

GRI-GM13 also permits alternative methods such as ASTM D1603 or ASTM D6370 when an appropriate correlation with the specified method has been established.

Carbon Black Dispersion Uses Microscopic Categories

ASTM D5596 evaluates carbon black dispersion in polyolefin geosynthetics using microscopic fields of view. The method provides a qualitative evaluation based on carbon black agglomerate size.^[4]

Under the GM13 dispersion criterion, ten different microscopic views are evaluated. For near-spherical agglomerates:

• Nine views must be in Category 1 or Category 2.
• One view may be in Category 3.

A report showing several Category 4 or Category 5 views does not satisfy this criterion.

Dispersion Is Not the Same as Distribution

ASTM D5596 explicitly distinguishes carbon black dispersion from carbon black distribution. The method evaluates agglomerates within prepared microscopic specimens; it does not prove that carbon black concentration is perfectly uniform across the full width, length, and thickness of every roll.^[4]

For this reason, project reviewers should check:

• Where the test sample was taken.
• How the sample is connected to the production lot.
• Whether the report includes ten views.
• Whether the categories are listed individually.
• Whether the report contains representative microscopy images where required.
• Whether carbon black content was tested separately.

Common Carbon Black Reporting Problems

Reject or clarify reports that contain:

• Carbon black content without a test method.
• A single percentage with no batch identification.
• “Carbon dispersion: Pass” with no category information.
• A supplier’s internal grade that cannot be connected to ASTM D5596.
• Content and dispersion combined into one result.
• Testing completed only on masterbatch rather than finished sheet.
• A claim that 4% or 5% carbon black automatically gives better UV performance.

How to Read Oxidative Induction Time

OIT Evaluates the Stabilization Level of the Formulation

Oxidative induction time is measured by differential scanning calorimetry. It is used as a quality-control indicator of the stabilization or antioxidant protection present in a polyolefin formulation.

OIT does not directly measure:

• Total geomembrane service life.
• Hydraulic conductivity.
• Chemical compatibility with a project liquid.
• Stress crack resistance.
• UV resistance under every climate.
• Field-weld durability.

ASTM D8117 describes Standard OIT as a qualitative assessment of material stabilization and warns that accelerated thermal-aging results can be misleading when used without understanding the additive package and test conditions. It also states that definitive relationships for using field-sample OIT values to determine life expectancy have not been established.^[5]

GRI-GM13 Allows Standard OIT or High-Pressure OIT

GRI-GM13 provides two alternative initial OIT methods:

The manufacturer has the option to select one of these methods for evaluating the antioxidant content unless the project specification requires both.

This means a report containing only a valid Standard OIT result is not automatically incomplete under generic GM13. Similarly, a report containing only a valid HP-OIT result may satisfy the initial OIT provision.

However, the report must not compare a Standard OIT result directly with the 400-minute HP-OIT requirement or compare an HP-OIT result with the 100-minute Standard OIT requirement.

ASTM D3895 Is an Outdated GM13 Reference

Older GM13 documents and many copied product data sheets identify ASTM D3895 as the Standard OIT test method.

GRI-GM13 Revision 16, dated March 17, 2021, updated the Standard OIT reference from ASTM D3895 to ASTM D8117. The current Revision 19 continues to reference ASTM D8117.^[1]

Standard OIT and HP-OIT Results Are Not Directly Interchangeable

Standard OIT and HP-OIT use different test conditions. Their numerical values should not be treated as equivalent indicators on a one-to-one basis.

ASTM D5885 uses high-pressure differential scanning calorimetry and explains that OIT depends on both the resin and additive package. It also warns that the result should not be used to estimate geomembrane lifetime directly.^[6]

The following conclusions are therefore invalid:

• “400 minutes HP-OIT is exactly four times better than 100 minutes Standard OIT.”
• “A product with 800 minutes HP-OIT must last twice as long as one with 400 minutes.”
• “The highest OIT value always identifies the best geomembrane.”

OIT results should be used to confirm minimum stabilization, formulation consistency, and antioxidant retention after defined aging exposures.

Oven Aging Uses Retained OIT

Initial OIT confirms the stabilization level before aging. GRI-GM13 also evaluates how much OIT remains after air-oven aging.

The GM13 oven-aging procedure uses ASTM D5721 at 85°C for 90 days. The retained OIT requirements are:

Retained OIT is calculated by comparing the aged result with the original unaged result:

OIT retention (%) = aged OIT result ÷ original OIT result × 100.

Example:

• Original HP-OIT: 520 minutes.
• HP-OIT after oven aging: 442 minutes.
• Retention: 442 ÷ 520 × 100 = 85%.
• Initial interpretation: the result exceeds the 80% retained HP-OIT criterion.

ASTM D5721 states that air-oven aging can be used to compare thermal-aging behavior and stabilizer packages, but it does not independently predict performance where stress, environment, temperature, and time interact.^[7]

UV Resistance Is Evaluated Separately

GRI-GM13 also includes a fluorescent UV-condensation exposure under ASTM D7238. The UV criterion is based on a minimum 50% retained HP-OIT value after 1,600 hours of exposure.

Standard OIT is not used for this UV-retention criterion because the higher Standard OIT test temperature can produce unrealistic results for some antioxidants in UV-exposed samples.

A report should therefore distinguish among:

• Initial Standard OIT.
• Initial HP-OIT.
• OIT retained after oven aging.
• HP-OIT retained after UV exposure.

Combining these into one row labelled only “OIT” makes the report difficult to audit.

Common OIT Reporting Errors

Request clarification when a report:

• Provides an OIT result without identifying Standard or High-Pressure OIT.
• Uses ASTM D3895 while claiming compliance with current Revision 19.
• Compares Standard OIT with the HP-OIT acceptance value.
• Reports aged OIT in minutes but does not calculate retention.
• Reports a retained percentage without the original and aged values.
• Uses initial OIT alone to claim a specific 50-year or 100-year service life.
• Omits the aging duration or exposure temperature.
• Uses a generic formulation report that cannot be traced to the offered product.

How to Read Stress Crack Resistance

HDPE Can Be Sensitive to Slow Crack Growth

Stress cracking is the development of cracking under sustained stress at a level lower than the short-term tensile strength of the material. The response can be influenced by resin microstructure, additive package, processing history, thermal history, loading, temperature, and surrounding environment.

Stress crack resistance is therefore evaluated separately from normal tensile strength.

A geomembrane can pass tensile yield and break-strength tests but still have inadequate resistance to slow crack growth.

GRI-GM13 Uses the ASTM D5397 Appendix Procedure

GRI-GM13 requires a minimum stress crack resistance of 500 hours using the ASTM D5397 Appendix single-point notched constant tensile load procedure, commonly abbreviated as SP-NCTL.^[1]

ASTM D5397 is an accelerated index test used to evaluate the susceptibility of polyolefin geomembrane sheet to stress cracking under a constant tensile load and accelerated environmental conditions.^[8]

Five Hundred Hours Is Not the Geomembrane Service Life

The 500-hour result is an accelerated laboratory acceptance threshold. It does not mean that the geomembrane will crack after 500 hours in a landfill or pond.

It also does not prove a specific field service life.

Field stress-cracking risk depends on factors including:

• Resin and formulation quality.
• Residual manufacturing stress.
• Field-weld geometry.
• Wrinkles and unsupported bridging.
• Localized settlement.
• Anchor-trench movement.
• Point loading and indentations.
• Chemical exposure.
• Temperature.
• Installation damage.
• Long-term tensile strain.

Correct interpretation: A result of at least 500 hours demonstrates that the tested formulation reaches the GM13 minimum SP-NCTL index requirement.

Incorrect interpretation: A result of 500 hours guarantees a particular number of years in service.

Stress Crack Testing Frequency Is Formulation-Based

GRI-GM13 links stress crack resistance testing frequency to GRI-GM10 and the formulation rather than requiring the test on every roll.

This makes formulation traceability critical.

The supplier should be able to connect:

• Resin producer and resin grade.
• Carbon black or masterbatch source.
• Antioxidant and stabilizer package.
• Manufacturing plant.
• Production process.
• Product surface type.
• Stress crack test report.
• Production lots supplied to the project.

If the resin or additive formulation changes, an old stress crack report may not represent the newly supplied material.

Do Not Replace SP-NCTL with ASTM D1693

Older polyethylene specifications may refer to environmental stress crack resistance under ASTM D1693. GRI-GM13 specifically uses ASTM D5397 Appendix SP-NCTL for its stress crack acceptance value.

A supplier should not describe an ASTM D1693 result as equivalent GM13 compliance without a project-approved technical basis.

How to Review Density, Carbon Black, OIT, and Stress Crack Results Together

Use a Combined Acceptance Table

No single result proves complete material quality. Review the properties as a connected formulation-control package.

This table provides only an initial review. Final acceptance still depends on:

• Correct test methods.
• Correct specimen preparation.
• Applicable GM13 revision.
• Product thickness and surface type.
• Testing frequency.
• Batch and formulation traceability.
• Laboratory competence.
• Project-specific specification.

Use the Results to Identify Different Types of Risk

Do Not Add the Results into a Single Quality Score

Density, carbon black, OIT, and stress crack resistance use different units and evaluate different characteristics. They should not be combined into an unofficial percentage score.

For example, it is technically weak to say:

• Density contributes 20 points.
• OIT contributes 30 points.
• Carbon black contributes 20 points.
• Stress crack resistance contributes 30 points.

A product that fails one mandatory property is not made compliant because it performs strongly in another property.

Other GRI-GM13 Properties That Must Still Be Reviewed

Thickness Must Match the Correct Surface Type

GM13 contains different thickness procedures for smooth and textured geomembranes.

Smooth geomembrane thickness is commonly evaluated under ASTM D5199. Textured geomembrane core thickness is evaluated under ASTM D5994 because surface asperities affect ordinary thickness measurements.

The report should identify:

• Nominal thickness.
• Average thickness.
• Lowest individual measurement.
• Measurement method.
• Smooth or textured surface.
• Weld-edge treatment for textured products.

A product should not be accepted only because its average thickness exceeds nominal. Localized measurements must also satisfy the applicable individual-value requirement.

Tensile Values Depend on Thickness and Surface Type

GRI-GM13 uses ASTM D6693 Type IV specimens for tensile testing.

Review:

• Yield strength.
• Break strength.
• Yield elongation.
• Break elongation.
• Machine-direction results.
• Cross-machine-direction results.
• Applicable smooth or textured table.
• Correct nominal thickness column.

Smooth and textured geomembranes have different break behavior and should not be compared using one universal elongation requirement.

Tear and Puncture Values Increase with Thickness

Tear and puncture requirements are thickness-dependent. A supplier must not use a 1.5 mm test value to approve a 2.0 mm product specification unless the value satisfies the correct 2.0 mm requirement.

Review the actual test units carefully. Test reports may use:

• Newtons.
• Pounds-force.
• Kilonewtons per meter.
• Pounds per inch.

Unit conversions should be checked rather than accepted from a copied data sheet.

Textured Products Require Asperity Review

For textured HDPE geomembranes, GM13 includes an asperity-height requirement measured under ASTM D7466.

Asperity height is a manufacturing index property. It is not a direct replacement for project-specific interface shear testing.

A geomembrane can meet the GM13 asperity-height requirement but still require ASTM D5321 interface testing with the actual project soil, geotextile, GCL, drainage geocomposite, or other adjacent material.

GM13 Does Not Include Every Project Property

Project-specific specifications may also require:

• Chemical compatibility testing.
• Permeation or diffusion assessment.
• Low-temperature performance.
• Site-specific interface shear testing.
• Multi-axial strain evaluation.
• Electrical leak-location compatibility.
• White-surface or conductive-layer properties.
• Site-specific puncture testing.
• Additional exposed-weathering evaluation.

These requirements should be listed separately rather than incorrectly described as universal GM13 properties.

How to Review Data Sheets, MQC Reports, and Conformance Testing

A Product Data Sheet Is Not a Batch Certificate

A product data sheet describes the manufacturer’s standard product. It commonly contains specification limits or typical values.

It should identify:

• Product name.
• Polymer type.
• Surface type.
• Available thicknesses.
• GM13 revision.
• Test methods.
• Units.
• Specified values.
• Document issue date.

It does not necessarily prove that the delivered rolls were tested.

An MQC Report Should Be Traceable to Production

A manufacturing quality-control report should provide actual production test results and connect them to identifiable material.

Request:

• Manufacturer and plant.
• Product designation.
• Nominal thickness.
• Surface type.
• Production date.
• Resin or formulation lot.
• Geomembrane production lot.
• Roll numbers.
• Sample identification.
• Test methods and versions.
• Actual results.
• Acceptance values.
• Test dates.
• Laboratory identification.
• Authorized review or approval.

Further information: Jinseed Geomembrane Quality Control.

Conformance Testing Provides an Independent Project Check

Purchasers may require samples from delivered rolls to be tested by an independent laboratory before installation.

The conformance-testing plan should define:

• Who selects the rolls.
• Who witnesses sampling.
• Sample dimensions and orientation.
• Chain-of-custody procedure.
• Testing frequency.
• Required laboratory competence or accreditation.
• Acceptance limits.
• Retesting procedure.
• Dispute-testing procedure.
• Responsibility for cost and schedule delays.

Independent testing should not use anonymous samples provided only by the supplier. Sample identification must connect the test result to the delivered roll and production lot.

Check Whether the Result Is Greater Than, Less Than, or Equal to the Limit

Report symbols matter.

GRI-GM13 Specification Review Checklist

Confirm the Document Basis

• Is the standard identified as GRI-GM13?
• Is the revision number and date stated?
• Is the material actually HDPE?
• Is the product smooth or textured?
• Does the nominal thickness fall within the applicable GM13 range?
• Does the project specification add more restrictive requirements?

Confirm the Four Key Formulation and Durability Properties

Confirm Report Traceability

• Are actual results provided?
• Are the units correct?
• Are current test methods identified?
• Are sample and batch numbers listed?
• Can the results be linked to delivered rolls?
• Does the report identify the resin or formulation represented?
• Were tests completed at the required frequency?
• Are individual and average results shown where required?
• Are aging-retention calculations visible?
• Are deviations clearly listed?

Request a Project-Specific HDPE Geomembrane Submittal

Jinseed supplies smooth and textured HDPE geomembranes for landfill, mining, wastewater, aquaculture, hydraulic, and environmental containment applications.

To prepare a technical submittal or quotation, provide:

• Application and project location.
• Required GRI-GM13 revision.
• Nominal thickness.
• Smooth or textured surface.
• Required roll width and length.
• Total quantity.
• Project-specific test requirements.
• Required MQC and third-party reports.
• Delivery destination and schedule.

Request an HDPE Geomembrane Specification and Quote

Buyers should request batch-specific results rather than relying only on a generic statement that the product is “GRI-GM13 quality.”

Technical Sources

1. Geosynthetic Institute, GRI-GM13 Revision 19 — Test Methods, Test Properties and Testing Frequency for HDPE Smooth and Textured Geomembranes, June 11, 2025.
2. ASTM International, ASTM D792-20 — Density and Specific Gravity of Plastics by Displacement.
3. ASTM International, ASTM D4218-20 — Determination of Carbon Black Content in Polyethylene Compounds by the Muffle-Furnace Technique.
4. ASTM International, ASTM D5596-03(2021) — Microscopic Evaluation of the Dispersion of Carbon Black in Polyolefin Geosynthetics.
5. ASTM International, ASTM D8117-21 — Oxidative Induction Time of Polyolefin Geosynthetics by Differential Scanning Calorimetry.
6. ASTM International, ASTM D5885 — Oxidative Induction Time of Polyolefin Geosynthetics by High-Pressure Differential Scanning Calorimetry.
7. ASTM International, ASTM D5721-22 — Air-Oven Aging of Polyolefin Geomembranes.
8. ASTM International, ASTM D5397-20 — Evaluation of Stress Crack Resistance of Polyolefin Geomembranes Using the Notched Constant Tensile Load Test.

Technical note: GRI-GM13 is a manufacturing quality-control specification for general HDPE geomembrane applications. Material selection, chemical compatibility, liner thickness, slope stability, installation procedures, seam testing, protection requirements, and project acceptance must follow the approved design and construction quality-assurance documents.