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About Rawell Environmental Ltd.

Rawell Environmental Limited is one of the worlds premier suppliers of bentonite based waterproofing materials. In fact it has been trading longer than most of the current suppliers of bentonite membranes having been formed over 30 years ago.

Where Rawell stands alone however is the form in which its products are supplied to the customer. The RAWMAT® HDB membranes and RAWSEAL® waterstops are unique in that they are the only bentonite products that are non-granular, pre-hydrated and manufactured by vacuum extrusion, a process which Rawell patented in the early 1990’s. Therefore the central core of natural sodium bentonite is already an impermeable barrier and does not require liquid to be added on site.

Rawell was founded by its current Chairman, Bryan Flynn, in 1976. After many years of experience in construction and civil engineering, including the construction of a bentonite processing plant, Bryan took a change of direction with his company by securing the UK distribution rights for the soil sealing and below ground waterproofing products of a large American mineral company.

Rawell developed a prosperous market and made bentonite waterproofing an established method of construction across the UK with a project list and client base of household names like The Channel Tunnel, Canary Wharf and BNFL. This market penetration was achieved and maintained by its high quality service and attention to detail.

The Original GCL

In 1982 Rawell were closely involved with the development of the worlds first Geosynthetic Clay Liner or GCL, a sandwich of dry granular bentonite between two geotextile fabrics. This product enabled a single versatile product to be supplied into a wide variety of applications and industries giving greater coverage of large areas in minimal time. Rawell took this product into a diverse cross-section of applications and supplied the first use of a GCL into a landfill application anywhere in the world. From this project spawned the growth of the use of the GCL as a replacement to compacted clay liners as the basal seal to landfills around the world.

Pre-hydrated vs. Dry Bentonite
Left: Pre-hydrated bentonite, note dense surface.
Right: Dry bentonite, note voids around particles

Despite its successes with this dry bentonite membrane, Rawell was experiencing a number of technical difficulties with the products and was dissatisfied with the speed and depth of the investigations carried out by the manufacturers. Rawell was able, through empirical evidence, to identify a number of technical deficiencies with the general type of dry bentonite products, which had become the industry standard. Research into these problems lead Rawell to revealing an inherent failing of “dry” bentonite membranes.

The crux of the problem with the dry bentonite systems is the importance of the correct hydration of the clay once placed in the ground, and the consequential effects of ionic exchange if the hydrating fluids are not compatible with the bentonite at initial hydration or some time in the future.

Improving the GCL

In keeping with its principles of providing its clients with provable, long-term solutions, Rawell set about investigating ways of overcoming these deficiencies and developing a process and a resultant product which would withstand the rigours of below ground application in arduous environments Following the principle that controlled hydration of the bentonite clay is critical to produce an effective functioning material, a process was developed and protected with patents, that produced a unique product that eliminated the weaknesses widely associated with “dry” or “granular” bentonite membranes and concrete sealing products.

The process, the monitored mixing of water and polymeric liquids, prior to the addition of a measured amount of bentonite powder, involves the controlled high speed high shear mixing to produce a pre-hydrated non granular bentonite/polymer alloy in both sheet and profile form. When extruded in sheet form the clay is laminated on line to form the internal core of a geotextile lined composite membrane, RAWMAT® HDB. The combination of the patented polymer mixture and the pre-hydration process prevents the chemical degradation that affects the other bentonite membranes in the market place.

These pre-hydrated bentonite products have proved exceptionally successful in providing robust engineering solutions to projects across the globe. Building on its initial success in the waterproofing of the underground rail link between Hong Kong Island and Chek Lap Kok Airport in Hong Kong, Rawell has supplied many major projects around the world. In doing so, Rawell has offered designers a flexible, efficient and cost effective solution to difficult engineering problems. Rawell products have been used on the Copenhagen Metro (Denmark), Preveza-Aktion Crossing (Greece), Britomart Underground Station (New Zealand), Manchester Airport (UK), Kuala Lumpur International Airport (Malaysia), Gardemoen Rail Link (Norway), Sechibaru Reservoir (Japan) and many successful waterproofing projects in Venice (Italy).

The RAWMAT® HDB and RAWSEAL® products are certified by the British Board of Agrément where it is uniquely stated that

“the system will provide an effective barrier to the transmission of liquid water for the life of the building in which it is incorporated.”

Research, Development & Quality Assurance

Rawell has since the inception of the pre-hydrated range of products, carried out extensive testing on its products to support its use in a wide variety of aggressive conditions, these tests are both ongoing and long term and carried out in independent laboratories around the world. The company continues to develop its product range and in 2000 Rawell were awarded a Government funded SMART award for its product development combining its technical knowledge and know how with the University of Leeds and TWI. Rawell is also heavily involved with links to Universities through the Government sponsored Knowledge Transfer Partnership (KTP) from which it has gained considerable success. Rawell also works closely with students on research projects across the world.

Whilst being a relatively small but very proactive company, Rawell’s clients benefit from the close personal attention this allows, it has the customer base and successful project history to match a much larger multi-national organisation. Rawell’s business is the manufacture and supply of pre-hydrated bentonite products to the Building and Civil Engineering markets only, it does not manufacture bentonite for other industries nor does it produce geotextiles or geomembranes. Rawell prides itself on its ability to offer respected technically engineered solutions to a wide variety of applications the world over. It supplies its products and services to a wide range of applications that can be categorised into four main market sectors, these are termed Petrochemical Lining, Structural Waterproofing, Environmental Protection and Landscaping.

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