When most hear about ground enhancement material they think of bentonite. The term Bentonite was first used for a clay found in about 1890 in Montana USA. Extracted bentonite is distinctly solid, even with a moisture content of approximately 30%. Bentonite is subsequently dried to reach a moisture content of approximately 15% and used in granular form or milled into powder and super fine powder form.
It is often impossible to achieve the desired reduction in ground resistance by adding more grid conductors or ground rods. An alternate solution is to effectively increase the diameter of the electrode by modifying the soil surrounding the electrode. With the price of copper on the rise, usually the most cost-effective solution is to include a ground enhancement material such as bentonite.
The main issues with using bentonite for backfill around the earthing anode (ground rod, copper tape, cable etc…) during installation is:
- Swelling of up to 25% occurs when wetted from dry state,
- Shrinkage occurs during drying from wet state
- Formation of a number of voids and small cracks
- Potential lack of contact with earthing anode = BAD earth
As great a product as it has been there is a superior option for Ground enhancement material that many are aware but most are not. Erico’s Ground Enhancement Material is considered one of the best enhanced options available on the market.
GEM has a resistivity of less than 0.12 Ω·m (about 5% of the resistivity of Bentonite). It typically placed around the rod in an augured hole or around earthing conductors in a trench in the same fashion as bentonite, in either a dry form or premixed in a slurry. GEM is a permanent material and will not leach any chemicals into the ground.
GEM from ERICO is a conductive material that improves grounding effectiveness, especially in areas of poor conductivity-rocky ground, areas of moisture variation, sandy soils. It is a preferred option for mining, government and private construction works, especially in locations with dry conditions and poor soil.
- 20 times lower resistivity than Bentonite clay
- Can dramatically lower the earth resistance and impedance measures
- Maintains constant resistance for the life of the earthing system
- Does not dissolve, decompose, leach out or require replacement or maintenance
- Does not require continuous presence of water to maintain its conductivity
- Exceeds IEC® 62561-7 which sets the benchmark
- Can be installed using trench or ground rod backfill methods
- Does not dissolve, decompose, or leach out with time
- Is non-corrosive and protects against corrosion to extend life of component
- Short and long-term cost and performance benefits
The table below is a comparison chart showing tests conducted that prove GEM (“IEEE 80-2000 14.5 Soil treatment to lower Resistivity) is a superior and preferred option as a ground enhancement material to bentonite.
|Material Form||% Water Content by Weight||Resistivity (ohm-cm)||
% Reduction from
|4||GEM25A||Slurry (Initial Measurement)||40%||126||53%|
|4||GEM25A||Cured 3 days||Cured||16.4||94%|
|4||GEM25A||Cured 75 days||Cured||6.9||97%|