Bentonite mat

  • Description
  • Laying technology
Bentonite mat

The Bentonite Mat (Geosynthetic Clay Liner) is a waterproof geosynthetic coating consisting of a layer of bentonite-granulated material, placed between two layers of geotextile (woven and non-woven) and then needle punched. The reasonable value of bentonite waterproofing for the consumer is that it doesn’t require any special skills during the installation process. Only simple instructions have to be followed. The Bentonite mats are cost-competitive in comparison to alternative waterproofings, especially considering not only material cost, but also installation works. Bentonite is an absorbent aluminium phyllosilicate clay consisting mostly of montmorillonite (around 70%). The property of swelling(up to 14-16 times) on contact with water in combination with weight (used to create enclosed space) leads to formation of gel-like low-permeable barrier(Bentonite Gel) of high density, with a permeability not higher then 3x10^(-11) m/s, which guarantees waterproofing of surface. The Non-woven geotextile, as a lower layer of Bentonite mat is impermeable to Bentonite Gel, while the Woven geotextile as a higher layer, has enough permeability to let slip small amounts of clay on the protected surface to “cure” possible cracks or imperfections. Strong and wear proof geosynthetic coating seals and protects the layer of bentonite clay, ensuring long-term usage of the Bentonite Mats.   

application

  • Waterproofing for lakes, dams, canals and other water storages and reservoirs
  • Horizontal and vertical waterproofing of underground surfaces: tunnels and foundations of the buildings
  • Protection of ground waters
  • Waterproofing of industrial waste landfills
  • Waterproofing of buildings and constructions in Oil&Gas, Mining, Automotive and Railway industries.
  • Construction of watertight screens and surface concrete membranes

Advantages

  • The Bentonite mat is self-healing: it swells, fills damaged zones with Bentonite Gel and seals the puncture.
  • One layer of Bentonite Mat having 6mm of width can replace 1 meter of clay waterproofing.
  • Bentonite is a natural, environmentally friendly, sustainable  and completely safe material.
  • Upon displacement or deformation of the foundation (eg. under seismic activity), the Bentonite mat does not lose its integrity and its use properties remain unaffected.
  • The Bentonite Mats can be installed on the basis of any shape, under almost any weather conditions and they don’t require any specialized equipment for the installation process.
  • Bentonite mats are durable and can overcome unlimited number of “hydrating-dehydrating” and “freeze/thaw” cycles without impacts on functionality.
  • Bentonite mat is resistant to hydrostatic pressure up to 70 meters of water column.
  • The permeability of material is not higher then 3x10-11 m/s;
  • The Bentonite mat has a low coefficient of thermal conductivity.
  • The Bentonite mat can be installed at very low temperatures, down to minus 50° С.

The Bentonite mat laying technology. Steps.

Supporting materials: granulated bentonite, bentonite sealant.

PREPARATION OF BASE

PREPARATION OF BASE

  • The surface, where the Bentonite Mat will be laid, should be cleaned from plant roots, stones and other items that may damage material.

  • It is essential to remove uneven surfaces exceeding 12 mm of variance.

  • Before the mat is laid on the sub-soil, the latter should be rammed, with a coefficient not less than 0.9

FIXING OF THE MAT ON THE TOP OF THE DIP SLOPE

FIXING OF THE MAT ON THE TOP OF THE DIP SLOPE

  • One edge of the roll is laid in the anchoring trench, dug along the perimeter of a ditch(pit) (this is not required for flat slopes).

  • The roll is unrolled in such a way, so it fully covers the pit bottom, but not covering the opposite side.  

  • The filling up of the pit should be backfilling, to avoid the descending of the mat down the slope.

INSTALLATION OF MATERIAL

INSTALLATION OF MATERIAL

  • During the installation of the mat it is important to avoid the friction of material with its foundation, in order to avoid the damage of the lower layer of the material.
  • The Bentonite Mat should be unrolled carefully, to avoid
    wrinkles and folds.
  • The sheets of material should be laid with overlap not less then 150mms (in length direction) and not less then 300mms (in width direction).

  • Bentonite mats should be unrolled in such a way, so in the places of overlaps the mat on top covers the one below;

  • Sheets of the bentonite mat are placed the woven party up, in one direction, with an overlap of 100-300 mm. In order to ensure additional reliability overlaps are sprinkled with bentonite granulate in amount of 0.8 kg / pm.

SEALING OF OVERLAPS AND PASSAGES FOR  ENGINEERING LINES AND CONSTRUCTION ELEMENTS

SEALING OF OVERLAPS AND PASSAGES FOR  ENGINEERING LINES AND CONSTRUCTION ELEMENTS

  • Places of overlaps between the top and the lower mat are sprinkled with bentonite granules;

  • Around a construction element the additional sheet of material keeps within, the place of a joint wakes up bentonite granules.

REPAIR OF DAMAGES

REPAIR OF DAMAGES

  • In case when bentonite mat was damaged during laying, then it is necessary to use patches, and apply the granulated bentonite or bentonite sealant around the damage.
ARRANGEMENT OF THE PROTECTIVE AND CLAMPING LAYER

ARRANGEMENT OF THE PROTECTIVE AND CLAMPING LAYER

  • Right after laying bentonite mats need to be clamped: cover with a layer of soil, sand or crushed stone that will create tension in material at hydration and will provide transformation of bentonite granulate to bentonite gel;

  • The bentonite mat is filled up with the fine-grained soil or other material provisioned by the project which should not contain particles bigger than 25 mm that can damage material;

  • In order to avoid premature hydration of the bentonite mat, it is necessary to daily lay only such its quantity which will be possible to cover with a protective layer of soil on the same day;

  • When placing the bentonite mat on vertical surfaces it is necessary to attach special attention to clamping for the material with guarantee to provide a waterproofing by formation of bentonite gel;

  • Minimum clamping force for a bentonite mat is 250 kg/sq.m.