What is the maximum permissible silt content for mortar sand?

It is generally restricted to 8% for natural sand and 10% for crushed sand to ensure adequate mortar strength.

What standard dictates the testing methods for this sand?

Testing methods for aggregates, including sand for mortar, are governed by IS 2386.

Why is grading of sand important for mortar?

Proper grading ensures a dense mix, reduces void ratio, minimizes cement consumption, and provides better workability.

IS 3118

: 1965

Specification for Sand for Use in Mortar

CurrentRareSpecificationMaterials Science · Aggregates and Sand

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This standard provides specifications for sand used in the preparation of mortar, detailing the required grading limits and maximum permissible levels of deleterious substances like clay and silt.

Lays down requirements for naturally occurring sand used as fine aggregate in mortars.

Quick Reference Values

max silt content natural sand8% by weight

max silt content crushed sand10% by weight

max clay lumps1% by weight

Practical Notes

Always account for the bulking of sand due to moisture when batching mortar by volume on site.

Excessive silt and clay content in sand significantly reduces the bond strength of the mortar and increases the risk of shrinkage cracks.

Ensure sand is properly sieved before use to remove oversized particles and organic impurities.