Bentofix® X – also known as geosynthetic clay barriers (GBR-C) – are needle-punched, reinforced composites that combine two durable geotextile outer layers and a uniform core of high-swelling powder sodium bentonite clay, with an additional polyethylene extrusion-coated barrier. This forms a uniform, multi-directional, shear-resistant, hydraulic, multi-component barrier with self-sealing and re-healing characteristics.
Bentofix® geosynthetic clay liners (GCL) exemplify how geosynthetics perform best: by interacting with natural elements to create something stronger or more secure.
The needle-punched manufacturing technology greatly increased the internal and external shear strength of GCLs and expanded the range of applications in which GCLs could be used. The needle-punching process firmly bonds the three unique layers of Bentofix® – two outer encapsulating geotextiles and the core of sodium bentonite. This bond creates a single, engineered barrier that utilises the best of both synthetic and natural materials.
Bentofix® GCLs outperform significantly thicker layers of compacted clay. The exceptional, immediate swelling characteristic of powdered sodium bentonite provides a long-term barrier that can “self-seal and re-heal” (e.g. swell to fill potential punctured/damaged zones) and rehydrate to renew the barrier even if it has been exposed to desiccation. The highly engineered geotextile outer layers provide outstanding protection against piping of the bentonite, durability to resist damage, and strength to manage the challenges inherent in barrier designs, such as for security on slopes and against ﬂuctuating heads.
The polyethylene coating is attached uniform and firmly onto the woven Bentofix® X component creating a durable bond with the needle-punched fibres. This ensures a very high fibre pull-out resistance and increases the long-term internal shear strength.
The Bentofix® X polyethylene extrusion coating ensures an immediate and enhanced barrier to gas and radon while protecting against desiccation and critical substances. In applications with high hydraulic gradients over coarse soils the additional Bentofix® X coating prevents bentonite piping. In other applications the barrier acts as a possible root barrier.
Bentofix® X GCLs are coated with a polyethylene layer on the slit-film woven side. Installed with the coating facing up, impermeability and performance against desiccation improve. In a test Bentofix® X was placed over a sand layer with the PE coating faced up. Bentofix® X was saturated for 3 weeks with water through the sand layer under a confining stress of 18kN/m² prior to the desiccation period at a temperature of 40°C and air humidity of 40%. During a period of 250 days the moisture content of the bentonite layer was monitored. The results show that a relative water loss of less than 10% occurred. Therefore it can be stated that Bentofix® X-types do not desiccate under these conditions.
Desiccation behaviour of geosynthetic clay liners in a laboratory test
The interface friction angle also plays a major role in slope applications. The mechanically bonded nonwoven of Bentofix® provides high interface friction angles. The structure of the polyethylene coating of Bentofix® X geosynthetic clay liners varies according to the thickness of the coating. Therefore, project- specific friction angles should be specified. For slope inclinations up to 2.5:1 (h:v) the extruded friction structure of Bentofix® X-types is typically suitable.
Example of shear stress of Bentofix® X coating against various materials at 20kPa confining stress
The polyethylene coating of Bentofix® X-types is manufactured from high-quality resins, which are comparable to those used in certified geomembranes. This gives the coating the necessary chemical resistance for long-term bentonite protection against critical substances.