Cement for hydraulic structures — Which cement is preferred for canal linings to enhance durability and reduce permeability?

Introduction / Context:
Canal linings demand durability against continuous water contact, reduced permeability to minimize seepage losses, and resistance to deleterious reactions. Selecting the proper cement type is a foundational decision in hydraulic engineering works.

Given Data / Assumptions:

• Structure: canal lining in permanent contact with water.
• Primary needs: low permeability, improved long-term durability, and resistance to aggressive ions common in soils and groundwater.
• Construction schedules are ordinary; ultra-rapid strength gain is not essential.

Concept / Approach:
Pozzolana cement (PPC) contains pozzolanic materials that react with calcium hydroxide to form additional calcium silicate hydrates. This secondary reaction densifies the matrix, reduces permeability, and enhances sulphate resistance compared with ordinary Portland cement, making PPC a common choice for canals and hydraulic structures.

Step-by-Step Solution:
Identify exposure: continuous wetting → need low permeability.Assess cement types: PPC reduces pores via pozzolanic reaction → better watertightness.Consider durability: improved resistance to sulphates relative to OPC (though dedicated sulphate resisting cement is for severe sulphate environments).Select cement: PPC offers balanced performance for typical canal linings.

Verification / Alternative check:
Field practice widely favors PPC in canals and water-retaining structures for reduced seepage and better long-term performance.

Why Other Options Are Wrong:
Sulphate resisting cement: excellent for severe sulphate exposure, but PPC generally suffices for typical canal conditions with added benefits of low permeability.Rapid hardening / Quick setting: chosen for speed or cold weather, not primarily for watertightness and long-term durability.High alumina cement: specialized, costly, and not standard for canal linings.

Common Pitfalls:
Confusing early strength needs with durability needs; canals prioritize permeability and durability.

Final Answer:
Pozzolana cement (PPC)