In This post we are going to cover

  • What is bentonite Clay
  • Benefits of using Sodium Bentonite Clay for dam or pond sealing
  • A Technical Explanation – for those interested in the tech side

What Is Bentonite Clay

Bentonite can be defined as a transported stratified clay which has been formed by weathering of volcanic ash approximately 66 million years ago. It consists of hydrated aluminum silicate or montmorillonite and is a member of the smectite group of minerals.

Sodium Bentonite is a natural clay that swells 12-24 times its original size when coming into contact with water. Bentonite clay is easily distinguished from other similar materials by its fineness and its highly absorbent nature which causes it to swell significantly when coming into contact with water.

There are different types of bentonites but the most common are produced in a granule (much like cat litter) and a fine powder form.

Bentonite clay contains Montmorillonite and this content varies greatly from one deposit to another which naturally has a huge impact on the clays swelling characteristics, therefore one should take care when evaluating local clay supplies as this will affect the subsequent membrane thickness that is applied.

Benefits of using Sodium Bentonite Clay for dam or pond sealing

There are several different methods used for the application of Sodium Bentonite, the most common being working the bentonite clay into the ground. When the dam or pond fills up, the bentonite swells up and fills all the cracks and seepage areas and will substantially reduces water seepage and in many cases may permanently stop water loss.

Dam Sealers – Diagram Showing Bentonites Sealing Properties

Sodium Bentonite is a very versatile material that can be used effectively in many different environments. Sodium Bentonite is eco-friendly, and being a clay is harmless to animals and fish.

Bentonite may be used as:

  • An additive to soil where the existing soils are inadequate to protect against water seepage – Mixed Blanket Application
  • A sediment sealant when it is applied as a waterborne material for deposition on the wetted perimeter. Sprinkle Application
  • A buried membrane by itself, which is similar to using bentonite as an imported material in a compacted liner. Pure Blanket Application

Our main use for Sodium bentonite is in sealing water bodies. The key to using bentonite to seal dams, ponds and streams is:

  • Always use a high-quality sodium bentonite
  • The bentonite needs to be applied 100% correctly to avoid future leaks
  • The amount of bentonite used must be based on the quality of your water and the soil type being treated.
  • Remember: Cheaper Is Seldom Better!!!

A Technical description – for those interested

Bentonite can contain either sodium or calcium as exchangeable cations absorbed on the clay structure which consists of linked three layer sheets or flakes. Unsatisfied charge within its sheets structure cause a negative surface charge. As a result bentonite has a strong affinity for cations and water molecules which on absorption are tightly bound within its particles. Whilst absorbing water molecules bentonite swells up to 24 times its dry volume and it is these two factors, its swellability and the fact that the water is tightly bound that makes bentonite so useful in environmental sealing applications.