No—not on GSM alone. A same-weight geotextile may be accepted as a replacement if it meets the project’s material, performance, durability, and installation requirements and receives the required approval. For example, a 300 g/m² product with a puncture strength of 2.0 kN does not meet a specified minimum of 2.5 kN, even though its weight matches.
The replacement does not necessarily need to reproduce every value on the original product’s data sheet. It must meet the governing project requirements, including any specified material type, product restrictions, and substitution conditions.
Numerical examples below illustrate the review process. They are not universal acceptance limits, current prices, or Jinseed product specifications.
Compare the Specification, Not Just GSM
FHWA identifies opening size, permeability, durability, and strength as design requirements for geotextile filters and separators.[1] The comparison below assumes the same test methods, conditions, and acceptance basis.
| Property | Project requirement | Proposed replacement | Result |
|---|---|---|---|
| Nominal mass per unit area | 300 g/m², with a specified tolerance | 300 g/m² | Nominal match; verification required |
| Machine-direction wide-width tensile strength | ≥15 kN/m | 18 kN/m | Meets requirement |
| Cross-machine-direction wide-width tensile strength | ≥15 kN/m | 13 kN/m | Below minimum |
| Static puncture strength | ≥2.5 kN | 2.8 kN | Meets requirement |
| Apparent opening size | ≤0.20 mm | 0.30 mm | Exceeds maximum |
| Water flow performance and durability | Evidence for specified service conditions | Not supplied | Cannot verify compliance |
This product does not qualify under the stated requirements. Its cross-machine strength is below the minimum, its opening size exceeds the maximum, and supporting data are missing. The two tensile directions cannot be averaged to obtain a pass. For this example, wide-width tensile strength, static puncture and apparent opening size must each be assessed using the method and edition specified for that property; a pass in one property cannot offset failure in another.
Check the Application and Material
When comparing PET non-woven geotextile grades, confirm the polymer and fabric construction first. Changing from PET to PP, or from nonwoven to woven fabric, can affect deformation, pore structure, and long-term performance.
For durability, give the reviewer the expected chemical exposure, temperature, design life, and time exposed to sunlight before burial. A generic claim such as “chemical resistant” does not establish suitability for those conditions.
| Application | Replacement checks |
|---|---|
| Road separation | Strength, puncture resistance, and applicable filtration properties. Check aggregate size and angularity, initial cover thickness, and compaction equipment against installation requirements. |
| Drain or shoreline filtration | Soil particle-size distribution, opening size, water flow capacity, and clogging risk. Consider reversing flow or high hydraulic gradients where present; soil–geotextile testing may be needed. |
| In-plane drainage | Flow capacity at the specified pressure, hydraulic gradient, and contact conditions. Results for water passing through the fabric do not establish flow capacity along it. |
| Geomembrane protection | Contact aggregate, cover load, liner type and thickness, and geotextile compression and puncture properties. Verify the combined system where existing evidence is insufficient. |
| Reinforcement | Load–strain behavior, creep and creep rupture over the design life, and reductions for installation damage and aging. Check interface and seam performance where specified. |
For filtration, a smaller opening size is not automatically better: the fabric must retain the soil while allowing sufficient flow without unacceptable clogging. For drainage, results measured under 20 kPa of pressure cannot simply be used for a 200 kPa application.
For reinforcement, a short-term tensile strength of 30 kN/m is not automatically an allowable long-term strength. FHWA design guidance accounts for creep, installation damage, and durability when deriving long-term reinforcement strength.[2]
For geotextile cushioning under a geomembrane, inspect subgrade preparation, overlaps, wrinkles, and placement damage before covering the material. A laboratory puncture result does not verify those site conditions.
Read the Reports on the Same Basis
Test Methods
ASTM D4595/D4595M uses the wide-width tensile method.[3] ASTM D4632/D4632M-15a(2023) measures grab breaking load and elongation.[4] A wide-width result of 15 kN/m and a grab result of 900 N cannot be compared by unit conversion; the specimens and loading arrangements differ.
Check method numbers, editions, units, and test conditions against the contract. GB/T, ISO, EN, and ASTM results are not automatically interchangeable.
Typical Values and MARV
A nonwoven geotextile data sheet may show a typical strength of 16 kN/m. That figure alone does not prove compliance with a required minimum average roll value of 15 kN/m.
MARV accounts for production variation and is commonly calculated as the average value minus two standard deviations. It is not an individual specimen’s lowest result.[5] Ask the supplier to identify the reporting basis for each property and provide values that match the project’s acceptance criteria.
Weight Tolerance
If the specified acceptance range is 300 g/m² ±5%, the limits are 285–315 g/m². An acceptance result of 280 g/m² falls outside that range. Whether one low specimen rejects a whole lot depends on the prescribed sampling and acceptance rules.
A 4 m × 50 m roll at 300 g/m² has a theoretical net mass of 60 kg. Deduct the core and packaging, and verify the actual dimensions if the weight differs substantially. Whole-roll weighing does not replace specimen testing.
Product and Batch Identity
If the report names Product A but the quotation names Product B, obtain evidence that the report applies to the offered material. At delivery, match roll labels to the approved model, manufacturing source, and batch records before sampling.
A report for one submitted sample supports that sample’s results. It does not, by itself, verify every grade or future production batch.
Can Higher or Lower GSM Be Used?
Higher GSM is not an automatic upgrade. A heavier product still needs suitable opening size, flow capacity, deformation behavior, and durability. It must also comply with any specified weight range.
Lower GSM may be acceptable under a performance-based specification. But if the contract sets a minimum of 300 g/m², a 280 g/m² product requires an approved change even when its other properties meet the stated limits.
Prepare the Substitution Request
- Confirm the requirements. Collect drawings, material specifications, referenced standards, and installation details. If the schedule says only “300 GSM,” request written clarification rather than assuming weight is the only criterion.
- Submit a comparison sheet. List each requirement beside the proposed value, method, reporting basis, and report number. Identify deviations and missing evidence.
- Obtain the required decision. Submit additional tests or technical justification where requested. The authorized project party should confirm the accepted product, permitted locations, and any testing or installation conditions in writing before substitution. A supplier quotation or unilateral material change is not project approval.
Compare Cost per Area Covered
At assumed prices of CNY 4.00/m² and CNY 3.60/m², buying 10,000 m² creates a material price difference of CNY 4,000. Roll width and overlaps can change the quantity needed to cover the same area.
| Item | 4 m roll width | 6 m roll width |
|---|---|---|
| Purchase price | CNY 3.60/m² | CNY 3.60/m² |
| Additional coverage width per strip | 3.70 m | 5.70 m |
| Material cost per square metre covered | 3.60 × 4 ÷ 3.70 ≈ CNY 3.89 | 3.60 × 6 ÷ 5.70 ≈ CNY 3.79 |
The tabulated costs describe incremental coverage in a large parallel layout. For N equal-length strips of width W and side overlap o, net coverage is length × [N × W − (N − 1) × o]. Use the actual layout for a finite installation. This calculation excludes end overlaps, cutting waste, freight, testing, and installation. The 0.30 m overlap is not an installation recommendation.
