What Sets Rawmat Apart From Other Bentonite Systems

John Stallard
  1. Rawmat is the only prehydrated bentonite membrane in the world. Rawell, the manufacturers of Rawmat, sold a US made dry bentonite membrane for over 10 years and had major issues with that product on many occasions. Rawmat evolved as Rawell found the causes of the issues with the dry bentonite and designed them out of the Rawmat by prehydrating with a liquid polymer which hydrates and protects the bentonite such that no matter what the liquid is which first come into the membrane.
  2. Rawmat only uses the highest grade of natural sodium bentonite, the bentonite is natural, not blended and sourced from Wyoming the “Rolls Royce” of bentonites. It has an in-service history of over 23 years all across the world. Many of the dry bentonite membranes use blended bentonite (sodium bentonite mixed with “fillers” to reduce the amount of sodium and bulk out the product whilst reducing the cost. Blended bentonite will not perform in the same way as the Rawmat and will not have the same longevity as Rawmat. The consistency of the blended and Chinese bentonites on the market are cheap alternatives which bear no resemblance to the Rawmat membrane
  3. Rawmat overlaps allow the creation of a bentonite to bentonite overlap, as the core of the membrane is of a plasticine consistency perforated geotextiles are used which allow the bentonite to flow through of seal seam, the other geotextiles used can be peeled back to form self-sealing overlaps. With the dry GCL’s they use a thick non-woven geotextile which cannot be peeled back and so it interferes with the passage of bentonite between the overlaps and allows "wicking" of liquid through the geotextile and hence the overlaps are suspect.
  4. The choice of geotextiles used in the production of the Rawmat material allow the bentonite to expand on contact with water and bond to the concrete surface of the walls and floors thus preventing tracking of liquid between the membrane and the concrete. Due to the dense nature of the geotextile and the fibres used to needle punch the textiles together the bentonite does not bond to the surface and water can track between the membrane and the structure.
  5. As mentioned above the bentonite bonds to the concrete and remains in a "gell-like" form, if the structure to which it is applied moves, the bentonite is able to move with the structure and maintain its bond and the integrity of the waterproofing
  6. Rawmat is described above as being like “plasticine”, consequently when the material is cut or handled there is no loss of bentonite from within the membrane. Dry bentonites on the other hand consist of loose powder or granules held between the sheets by the needle-punched geotextiles. When these products are cut or handled the bentonite falls out at the overlaps and moves within the sheets. As stated above the overlaps are a weak part of the system and so if bentonite is lost this will make the overlaps even more susceptible than before.
  7. As outlined in 1 above, the Rawmat membrane is manufactured by hydrating the bentonite during the manufacturing process. The patented liquid cocktail of polymers used in the Rawmat impart chemical resistance into the core of the bentonite which out performs any other form of bentonite membrane. Rawmat has been under long term test with a wide variety of chemicals, hydrocarbons, saline solutions and calciferous soils and continues to perform. The prehydration with the Rawell polymer prevents cation exchange occurring in the Rawmat membrane. Cation exchange can break down the dry bentonite membranes as they absorb contamination during the hydration process then break down from within as the Sodium bentonite converts to calcium bentonite causing it to shrink, crack and leak. Rawmat has a proven resistance to cation exchange.
  8. The prehydration of the Rawmat does not affect the swell performance of the Rawmat membrane it still has the capacity to swell further and will self-heal should it suffer minor damage or punctures
  9. Rawmat has a successful 16 year history in New Zealand and 23 year history around the world. The first phase of Britomart underground, constructed in a saline environment and subject to minor structural movement, was completed using Rawmat and it remains watertight to this day. Around the world major projects such as Hong Kong Airport Rail Link and the Copenhagen Metro have been operating successfully with waterproofing provided by Rawmat.
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