Skip to content

Bentofix® + X Geosynthetic clay liner

Naue Bentofix® + X is a Thermal Lock GCL with enhanced oxidative resistance for mining, landfill and hydraulic engineering.

Request project consultationView technical information
  • Close-up of a coated Bentofix® + X bentonite mat (geosynthetic clay liner) showing the bentonite and PE coating layers.
  • Aerial view of a construction site with Bentofix® for a securely sealed tailings pond (TSF) as part of a mining facility.
  • Photo of a landfill construction site where Bentofix® geosynthetic clay liners are installed on steep landfill capping slopes.
  • Bentofix® + X is a Thermal Lock multicomponent GCL/GBR-C with an enhanced PE coating for superior long-term oxidative resistance.
  • Dual barrier: Thermal Lock PE seals immediately, the bentonite core self-seals on hydration; the enhanced + formulation resists oxidative ageing beyond GM13 requirements.
  • Three grades with extended OIT: +X2 (smooth PE), +X5F and +X10F (structured PE) - full range in technical data.
  • CE (CPR), ISO 9001, DIN 18200, EPD - full list in technical data.

Bentofix® + X is a Thermal Lock multicomponent geosynthetic clay liner with enhanced oxidative resistance for mining, landfill and hydraulic engineering. You install it between the subgrade and the protective cover layer. The Thermal Lock PE coating provides an immediate hydraulic and gas barrier from day one. The ‘+’ designation marks an advanced PE formulation with extended OIT and HPOIT values for superior long-term coating durability in harsh oxidative environments.

Mining and industrial containment environments subject PE coatings to prolonged oxidative stress from acid rock drainage, aggressive leachate and UV exposure. Conventional PE-coated GCLs meet minimum GM13 oxidation resistance. In permanently aggressive oxidative environments, antioxidant depletion accelerates and the effective coating service life is shortened. Bentofix® + X solves this. The unique resin and batch composition of the ‘+’ coating extends the OIT induction period far beyond GM13 requirements, delivering a measurably longer design life for the PE barrier.

Bentofix® + X extends the service life of the liner system in oxidatively challenging environments. Longer coating lifetime reduces the risk of premature barrier replacement, the largest cost in mining liner systems. The PE coating eliminates the need for a separate geomembrane layer in many applications and enables a 50% reduction in cover soil thickness compared to standard GCL applications.

The PE coating achieves k ≤ 10⁻¹⁴ m/s (EN 14150, calculated). Internal shear strength ≥ 35 kPa at 20 kPa (EN ISO 12957-1, 900 cm²). +X5F achieves interface friction ≥ 9 kPa at 20 kPa vs 300 g/m² Secutex® nonwoven (ASTM D6243). +X10F achieves interface friction ≥ 15 kPa at 20 kPa (ASTM D6243, based on confirmed X10F NSP 4900 spec). Extended OIT and HPOIT values of the ‘+’ coating exceed GM13 requirements.

Bentofix® + X geosynthetic clay liner functions:

  • Barrier

    Barrier

    Bentofix® + X creates a dual hydraulic and gas barrier. The Thermal Lock PE coating (k ≤ 10⁻¹⁴ m/s) acts immediately from installation. The bentonite layer (approx. 10⁻¹¹ m/s) self-seals on hydration. Two independent sealing barriers in series.

  • Separation

    Separation

    The PP geotextile layers maintain the bentonite core in position. They separate the bentonite from adjacent soil layers during installation and throughout service life.

  • Protection

    Protection

    The enhanced Thermal Lock PE coating protects against desiccation, ion exchange (Ca²⁺, Mg²⁺), root penetration and piping. The extended OIT/HPOIT ‘+’ formulation provides chemical protection and anti-ageing performance beyond GM13 in oxidative environments.

Bentofix® + X geosynthetic clay liner advantages: extended oxidative resistance and proven mining performance

Bentofix® + X delivers the full performance profile of Bentofix® X with one critical upgrade: a ‘+’ PE coating engineered for extended service life in harsh oxidative environments.

  • Safety

    Extended oxidative resistance

    The ‘+’ formulation delivers extended OIT and HPOIT values beyond conventional GM13 requirements (ASTM D3895, D5885). Delays antioxidant depletion in aggressive leachate, acid rock drainage and high-temperature climates, extending coating service life measurably beyond standard Bentofix® X.

  • Speed

    Immediate dual barrier

    Thermal Lock PE coating acts as an immediate hydraulic and gas barrier (k ≤ 10⁻¹⁴ m/s) from day one. The bentonite core self-seals on hydration (k approx. 10⁻¹¹ m/s). No hydration window for gas or leachate penetration.

  • Slope friction

    Superior slope friction

    +X5F (500 g/m², 0.4 mm nod height): interface friction ≥ 9 kPa vs 300 g/m² Secutex® nonwoven at 20 kPa (ASTM D6243). +X10F (~1,000 g/m², ~0.9 mm nod height): interface friction ≥ 15 kPa at 20 kPa. Confident slope stability design for 1V:2.5H and steeper.

  • Chemical and ion exchange protection

    Chemical and ion exchange protection

    PE coating shields bentonite from Ca²⁺, Mg²⁺, K⁺ ions in aggressive mine leachate. Enhanced chemical resistance due to advanced ‘+’ resin composition. Prevents bentonite degradation in acidic process water and brine.

  • No delamination risk

    Thermal Lock: No delamination

    Fibres permanently integrated into the PE coating during manufacturing. No shrinkage or delamination in high-temperature climates confirmed by laboratory desiccation test (300 days at 40°C, 18 kN/m²). Every roll needle-detector tested across full width.

Application areas

Typical applications:

  • Tailings storage facility (TSF) base liner and side slope in acidic, oxidative process water environments
  • Heap leach pad liners for gold, copper and silver operations with aggressive chemical solutions
  • Mine water evaporation ponds and process water retention basins in hot and arid climates
  • Secondary containment for tank farms, hazardous chemical storage and industrial facilities

The ‘+’ PE coating is the first line of defence against oxidative degradation from acid rock drainage, saline brine and chemical reagents. Standard GCL PE coatings meet minimum GM13 requirements, but in permanently aggressive oxidative environments, antioxidant depletion occurs faster. Bentofix® + X delays this through its extended OIT/HPOIT formulation. The +X5F and +X10F structured surfaces deliver high friction angles on embankment slopes, enabling confident slope stability design at steep inclinations.

Advantages:

  • Extended OIT/HPOIT: PE coating outlasts conventional GM13-compliant coatings in oxidative mining environments
  • Slope stability: +X5F ≥ 9 kPa; +X10F ≥ 15 kPa interface friction at 20 kPa (ASTM D6243)
  • Self-sealing: if the PE layer is damaged, the bentonite re-seals on hydration, reducing remediation costs
Aerial view of a construction site for a securely sealed tailings pond (TSF) as part of a mining facility.

To the application:

Mining

Typical applications:

  • Landfill base liner systems with aggressive leachate chemistry requiring extended PE coating durability
  • Landfill capping and closure systems in high-temperature or arid climates with desiccation risk
  • Gas containment liners for landfill gas management with immediate barrier requirement
  • Industrial waste containment, soil encapsulation and brownfield site redevelopment

The ‘+’ PE coating resists chemical attack and oxidative ageing beyond conventional GCL performance. The process ensures the PE coating remains firmly bonded in high-temperature conditions. Laboratory testing confirmed no desiccation of Bentofix® X under 18 kN/m² confining stress at 40°C and 40% air humidity over 300 days. This applies to Bentofix® + X with equivalent GCL construction.

Advantages:

  • Enhanced chemical resistance: ‘+’ PE coating formulation resistant to aggressive leachate and industrial chemicals
  • Immediate gas barrier: no methane migration during the hydration window, critical for landfill cap systems
  • Cover soil reduction: 50% reduction possible vs. standard GCL applications (confirmed at Stuart Landfill with X10F)
Photo of a landfill construction site where Bentofix® geosynthetic clay liners are installed on steep landfill capping slopes.

To the application:

Landfill engineering

  • Hydraulic engineering

    • Dams, reservoirs and canals requiring long-term PE barrier durability
    • Flood protection embankments with UV and oxidative exposure

  • Groundwater protection

    • Secondary containment for chemical and tank farm facilities
    • Retention basins for industrial runoff with oxidative chemistry

  • Environmental and industrial

    • Soil encapsulation for contaminated land with persistent organic pollutants
    • Reactive waste containment in post-industrial environments
    • Embankment waterproofing at steep inclinations (1V:2.5H or steeper)

  • Radon and gas barriers

    • Building foundation sealing against radon and soil gas
    • Gas containment in brownfield redevelopment projects

Technical properties

PropertyUnitBentofix® + X5F NSP 4900Bentofix® + X10F NSP 4900
Polyethylene coating – oxidative resistance (the defining property of the "+" types)
Oxidation induction time (OIT)min200200
High-pressure oxidation induction time (HPOIT)min600600
Residual OIT and HPOIT after oven ageing—Required values presentRequired values present
Reference requirement GRI-GM13 (for comparison)
Oxidation induction time (OIT)min≥ 100≥ 100
High-pressure oxidation induction time (HPOIT)min≥ 400≥ 400
Product configuration
Coating surface—Embossed, structuredEmbossed, structured
Bentonite core type—NSP 4900NSP 4900
Macro comparison of a conventional PE-coated geosynthetic clay liner (left) and Bentofix® + X (right). The left side illustrates an oxidised and embrittled PE coating above granular bentonite, while the right side shows an intact Thermal Lock PE coating with integrated fibres extending through the bentonite layer, forming a continuous composite structure.
Macro comparison of a conventional PE-coated geosynthetic clay liner (left) and Bentofix® + X (right). The left side illustrates an oxidised and embrittled PE coating above granular bentonite, while the right side shows an intact Thermal Lock PE coating with integrated fibres extending through the bentonite layer, forming a continuous composite structure.
Conceptual comparison of a conventional PE-coated GCL and Bentofix® + X. Extended OIT and HPOIT values help delay oxidative ageing of the PE coating, while the Thermal Lock manufacturing process permanently integrates needle-punched fibres into the coating. The result is a continuous composite structure with a durable PE barrier and a redundant bentonite sealing layer for demanding mining and tailings storage applications.
Conceptual comparison of a conventional PE-coated GCL and Bentofix® + X. Extended OIT and HPOIT values help delay oxidative ageing of the PE coating, while the Thermal Lock manufacturing process permanently integrates needle-punched fibres into the coating. The result is a continuous composite structure with a durable PE barrier and a redundant bentonite sealing layer for demanding mining and tailings storage applications.

Why extended OIT and Thermal Lock matter in mining and tailings storage

All PE-based barriers age predictably: antioxidants added during manufacturing absorb reactive oxygen; once the reservoir is depleted, the OIT induction period ends and the polymer itself oxidises and embrittles. Depletion is driven by oxygen availability, temperature, UV exposure and the aggressiveness of the contacting liquid - all present simultaneously in mining applications such as heap leach pads, tailings facilities and acid rock drainage containment. Conventional PE-coated GCLs meeting only minimum GM13 (ASTM D3895) OIT requirements may not perform adequately there.

The '+' in Bentofix® + X addresses this: a unique resin and batch composition raises the OIT (ASTM D3895) and HPOIT (ASTM D5885) of the Thermal Lock PE coating beyond conventional GM13 thresholds, extending the induction period and the coating's effective service life. The Thermal Lock process permanently integrates needle-punched fibres into the coating - no delamination risk in hot climates, consistent bond strength and a uniform barrier profile. Testing showed no desiccation over sandy material after 300 days at 18 kN/m² confining stress, 40 °C and 40 % air humidity.

The bentonite adds redundancy: should the coating be damaged or degrade, sodium bentonite self-seals on contact with water. +X5F achieves ≥ 9 kPa interface friction at 20 kPa, +X10F ≥ 15 kPa (ASTM D6243).

Naue Portal - the free digital platform for geotechnical engineers.

Naue Portal: your all-in-one free geotechnical software solution for planning and cost estimation

  • One platform – multiple solutions: access a wide range of geotechnical design tools in a single portal.
  • User-friendly and accessible: available anytime, anywhere via desktop or mobile.
  • Optimised cost and material usage: reduce construction costs while ensuring long-term project stability.
  • Compliant with industry standards: aligns with AASHTO, and other engineering guidelines.
Overview of all featuresRegister now

Frequently asked questions

Bentofix® + X is a Thermal Lock multicomponent geosynthetic clay liner (GCL) and geosynthetic clay barrier (GBR-C) from Naue. It combines a sodium bentonite core needle-punched between PP geotextile layers with an enhanced extrusion-coated PE layer permanently bonded to the woven carrier. The ‘+’ designation marks an advanced PE formulation with extended OIT (Oxidative Induction Time, ASTM D3895) and HPOIT (ASTM D5885) values, providing longer coating resistance against chemical attack and ageing vs. standard Bentofix® X. Two independent sealing barriers in one product.

Pricing depends on project volume, variant (+X2, +X5F, +X10F), bentonite type (BFG, NSP) and project location. Bentofix® + X carries a premium vs. standard Bentofix® X due to the enhanced ‘+’ PE coating formulation. Request a project-specific quote via the contact form below or contact info@naue.com.

Both are Thermal Lock multicomponent GCLs with the same needle-punched construction, bentonite core and variant range (+X2/X2, +X5F/X5F, +X10F/X10F). The critical difference is the PE coating formulation. Bentofix® + X uses an advanced resin and batch composition that delivers extended OIT and HPOIT values beyond the standard X coating and beyond conventional GM13 requirements. This provides measurably longer coating durability in harsh oxidative environments. For applications where standard OIT values satisfy the design, Bentofix® X is the cost-effective choice.

+X2 has a smooth ‘+’ PE coating (200 g/m²). Use for waterproofing, pond liners, flat installations and applications where slope friction is not critical. +X5F has a structured ‘+’ coating (500 g/m², 0.4 mm nod height) providing ≥ 9 kPa interface friction at 20 kPa (ASTM D6243). Use for TSF and landfill side slopes. +X10F has a heavy structured ‘+’ coating (~1,000 g/m², ~0.9 mm nod height) providing ≥ 15 kPa interface friction for the steepest embankment slopes. All three variants are available in BFG 5300 and NSP 4000/4900 types.

OIT (ASTM D3895) and HPOIT (ASTM D5885) measure the oxidative resistance of a PE barrier coating. Once the antioxidant reserve is depleted, the PE coating begins to degrade and embrittle. In mining environments, heap leach pads, TSF with acid rock drainage and evaporation ponds in hot climates, oxidative stress is continuous. Standard PE-coated GCLs meeting GM13 minimums may not provide adequate long-term performance. Bentofix® + X extends the OIT induction period through its unique resin and batch composition.

One square metre of Bentofix® + X (~10 mm installed) replaces up to 400 mm of compacted clay liner. This reduces excavation volumes, clay import and transport movements. The PE coating allows a 50% reduction in cover soil thickness compared to standard GCL applications in capping, as confirmed at Stuart Landfill, Australia (100,000 m², X10F). Longer coating service life reduces the risk of liner replacement, the largest cost in mining liner systems

Bentofix® + X carries CE marking, is produced under ISO 9001 quality management and DIN 18200 third-party monitoring. An EPD covers the Bentofix product family (EN 15804:2012+A2:2019, 2020).

Naue has published an EPD for the Bentofix® product family covering the full lifecycle (A1 to C4).

The Thermal Lock needle-punched composite construction provides high installation damage resistance. The Thermal Lock process permanently integrates fibres into the ‘+’ PE coating, preventing delamination in hot climates confirmed by laboratory testing (300 days, 40°C, 18 kN/m²). Every roll is needle-detector tested across its full width. Tensile strength: 14/14 kN/m md/cmd (+X2, EN ISO 10319); 22/22 kN/m (+X5F BFG 5300). Static puncture: 2,500 N (+X2); 3,300 N (+X5F). Roll dimensions: 4.85 m x 40 m (194 m²). Overlaps sealed with Bentofix® X Tape B.

Bentofix® + X BFG 5300 rolls: 4.85 m wide x 40 m long (194 m² per roll). This is the same as Bentofix® X. NSP type roll dimensions are the same (4.85 m x 40 m). The 30 cm overlap zone is pre-marked on the PE layer of every roll.

DIN 18200 (third-party monitoring), CE marking, ISO 9001. Testing per: EN ISO 10319 (tensile strength), EN ISO 12957-1 (internal shear strength), ASTM D6496 (peel strength), ASTM D6243 (interface friction), EN 16416 / ASTM D5887 (GCL hydraulic conductivity), EN 14150 (PE layer k), ASTM D3895 (OIT), ASTM D5885 (HPOIT). OIT and HPOIT values exceed GM13 minimum requirements.

Yes. Naue provides engineering support for mining and containment liner projects including slope stability calculations, liner system design, OIT/chemical compatibility analysis, specification preparation and installation supervision. Contact info@naue.com or submit a project request via the contact form below.

Conventional PE-coated GCLs meeting GM13 (GRI GCL3) requirements must achieve minimum OIT values at specified test conditions (ASTM D3895). Bentofix® + X exceeds these minimum values through its unique ‘+’ resin formulation.

Yes. Bentofix® + X is a preferred GCL solution for heap leach pad liner systems. The ‘+’ PE coating provides the oxidative resistance needed in aggressive acid leach solutions used in gold, copper and silver heap leaching. The PE coating shields the bentonite from cation exchange with saline reagents. The bentonite provides a redundant sealing function. The +X5F (≥ 9 kPa) and +X10F (≥ 15 kPa) structured surfaces deliver high friction angles for slopes where the heap loads onto the liner. Contact Naue engineering for site-specific liner system design.

Let’s discuss your project!

Please use the form to tell us about your enquiry
(* = required field)

Where to meet Naue next

All eventsAll webinars