Identification of deleterious salts in fine aggregates — likely source Sand is most likely to contain harmful soluble salts (chlorides, sulphates) if it is obtained from:

Introduction / Context:
Soluble salts in fine aggregates can cause efflorescence, corrosion of reinforcement, and setting/strength problems. Aggregate source strongly influences salt content and the extent of washing required before use.

Given Data / Assumptions:

• Natural sands from typical sources.
• No special washing or desalination has been performed.
• Marine environments contain dissolved salts.

Concept / Approach:

Sea-bed sands are immersed in saline water, making chlorides/sulphates prevalent. River and nala sands may contain silt or organic impurities but usually carry much lower salt concentrations than marine sands. Therefore, marine sands require thorough washing/desalination and are often restricted by specifications.

Step-by-Step Solution:

Verification / Alternative check:

Standards specify chloride limits in aggregates and caution specifically against unwashed marine sand.

Why Other Options Are Wrong:

• Nala/river sands can have clay/organic matter but not typically high salt levels like sea sand.
• “All” overstates the salt problem for freshwater sources.

Common Pitfalls:

• Using unwashed marine sand in reinforced concrete can accelerate corrosion.

Final Answer:

Sea beds (marine sources).