Bentonite earth electrode backfill
Bentonite is a sodium activated montmorillonite which, when mixed with water, swells to many times its dry volume. This enables moisture to be absorbed from the surrounding soil (e.g. rainfall), solving any soil to earth rod contact problems.
Bentonite moisture-retaining clay is commonly used as a backfill for earth rods installed in drilled holes, or as a layer encapsulating horizontal earth conductors buried in a trench.
Its main advantage as far as earthing is concerned is that it has the ability to retain moisture in the immediate vicinity of an earth rod, and hold it there for a considerable period of time. This reduces contact resistance and increases the effective size of earth electrodes.
Features & benefits:
Absorbs up to five times its weight in water
Swells up to thirteen times its dry volume which greatly improves contact resistance
Protects electrode and does not change characteristics as time elapses
Suitable for use in trenches and particularly boreholes
Cost-effective as requires less product when compared with cement-based solutions
The installed resistivity of Bentonite varies from about 3 Ohm metres upwards depending on its moisture content