The GATE Grind

GATE 2026 AG – Question 24

Soil and Water Conservation Engineering · Watershed Management · 1 mark · Multiple choice

Which natural colloidal clay absorbs water and swells to 8–15 times its dry size, and is used to seal farm ponds?

  1. EPDM (ethylene propylene diene monomer)
  2. Butyl
  3. Bentonite
  4. Soil cement

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Correct answer: (C) Bentonite

Explanation

Bentonite contains swelling clay minerals, especially montmorillonite. Hydration expands the material and reduces permeability when it is properly incorporated into the sealing layer. EPDM and butyl are synthetic lining materials, and soil cement is a stabilized mixture. The natural swelling clay is **bentonite, C**.

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