Question

A natural colloidal clay, having the characteristics of absorbing water and swelling 8 to 15 times its dry size, used as an efficient and effective sealing material for farm ponds, is

• A. EPDM (Ethylene Propylene Diene Monomer)
• B. Butyl
• C. Bentonite
• D. Soil cement

Hint:

Recall which farm pond liner material is a natural clay rather than a synthetic sheet.

Answer 1

The Correct Option is C

Farm pond linings need a material that seals the pond bed against seepage, and several materials are used depending on cost and availability.

1. EPDM (Ethylene Propylene Diene Monomer): EPDM is a synthetic rubber sheet liner, not a natural clay, so it does not fit the description of a colloidal clay that swells with water.
2. Butyl: Butyl is also a synthetic rubber membrane liner used for ponds, not a naturally occurring clay mineral.
3. Bentonite: Bentonite is a natural colloidal clay, rich in montmorillonite, that absorbs water and swells to several times its dry volume, typically about 8 to 15 times, forming a tight, low permeability seal on the pond bed.
4. Soil cement: Soil cement is a mixture of soil and cement compacted as a lining, an engineered blend rather than a natural swelling clay.

The natural colloidal clay described here is bentonite, option (C).