Environmental Protection: Introduction

RAWMAT^® HDB pre-hydrated natural sodium bentonite membranes are manufactured by Rawell Environmental Ltd for use in a wide range of construction, industrial and environmental uses. In Environmental Protection applications the materials act as a barrier to the passage of water, contaminates and vapours in a wide variety of industrial and pollution prevention applications.Applications for the RAWMAT^® HDB membrane include the basal lining and capping off of domestic, industrial and toxic landfill sites.

The resistance of the pre-hydrated bentonite core makes the system the ideal material for the repair and re-lining of hydrocarbon containment facilities whether the lining of aviation fuel storage bunds or the sealing of domestic transformer bunds. Both the re-lining of existing sewage treatment tanks or the creation of totally new reed beds have been completed successfully all over the UK. In addition the RAWMAT^® HDB system has been used to line trenches to protect the surrounding ground from leaks from contaminated pipelines and also to protect pipelines when passing through contaminated ground.

A major advantage of the RAWMAT^® HDB membranes is the simple method of sealing of the sheets at overlaps. The RAWMAT^® HDB membranes, regardless of the product Type, all provide intimate self sealing joints without the need for welding or adhesives at the overlap. No wicking (loss) of liquid occurs through the overlap or through the geotextile carrying fabrics.

In addition the choice of the geotextile carriers ensures that a bentonite seal is created between the RAWMAT^® HDB and any overlying geomembrane used in a composite lining system, thus preventing the tracking of liquid in the event the geomembrane is punctured. The plasticine like central core ensures that there is no movement of clay between the geotextiles in handling (therefore there are no bald patches between the fabrics) and no loss of the bentonite when the sheets are cut. RAWMAT^® HDB membranes do not need sand blindings below the membrane or sand cushions above them. Likewise the geotextile carrying fabrics incorporated within the membrane remove the need for protective geotextiles.

The main advantage of the pre-hydrated RAWMAT^® HDB is the proven resistance of the bentonite core to The natural sodium bentonite in RAWMAT^® HDB membranes and RAWSEAL^® waterstops is pre-hydrated with a patented polymer solution which provides a permanent protection to the ionic fingerprint of the clay protecting it from exchange and subsequent breakdown in ground contaminants, a drawback associated with other bentonite systems. As a result the RAWMAT^® HDB will perform its function without significant reduction in the k value or permeability of the membrane.

The use of RAWPASTE mastic and additional strips of RAWMAT^® HDB ensures extremely simple sealing of pipe penetrations, drainage and monitoring wells and systems without the need for complex and expensive accessories.

RAWMAT^® HDB membranes offer the best of both worlds - long term performance with installation economy. From the designers point of view you have a simple but highly chemical resistant membrane ideally suited to a wide variety of environmental protection applications, from the contractors perspective you have cost and time saving installation from a product which can self heal punctures.

The winner in all this is the client who gets the highest quality protection at a favourable cost and with shorter programmes than any other system.

Rawell products have been used extensively to overcome difficult ground conditions or arduous design criteria on projects all over the world. See Case Histories or Projects List to find just where the benefits of pre-hydrated bentonite have been experienced.