What is the required soaking time for the water absorption test?

The aggregate sample must be immersed in water at room temperature for 24 hours before testing.

Why is it important to measure the bulking of fine aggregate?

Moisture causes sand particles to push apart, increasing volume. Without correcting for bulking, volume batching results in significantly less sand in the actual concrete mix.

What is the proper temperature for oven drying aggregates?

Aggregates should be dried in a well-ventilated oven at a temperature of 100 to 110 °C.

IS 2386 Part 3

: 1963

Methods of Test for Aggregates for Concrete - Part 3: Specific Gravity, Density, Voids, Absorption and Bulking

CurrentEssentialTesting MethodMaterials Science · Concrete

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This standard specifies the methods for determining the specific gravity, apparent specific gravity, water absorption, bulk density, voids, and bulking of fine and coarse aggregates to evaluate their suitability for concrete mixes.

Covers methods for determining specific gravity, bulk density, voids, water absorption, and bulking of fine aggregates.

Quick Reference Values

Oven drying temperature100 to 110 °C

Soaking time for absorption test24 ± 0.5 hours

Standard testing temperature27 ± 2 °C

Tamping rod dimensions16 mm diameter, 600 mm long, rounded at one end

Key Formulas

Specific Gravity = A / (A - B) (where A = weight of oven-dried sample in air, B = weight of SSD sample in water)

Water Absorption (%) = 100 * (C - A) / A (where C = weight of SSD sample in air)

Percentage of Voids = 100 * (Gs - (Bulk Density / 1000)) / Gs

Bulking (%) = 100 * (V1 - V2) / V2 (where V1 = volume of wet sand, V2 = volume of inundated/dry sand)

Practical Notes

Accurate determination of water absorption is crucial for concrete mix design (IS 10262) to calculate the free water-cement ratio correctly.

When using volume batching on site, ignoring the bulking of sand can lead to under-sanded, harsh concrete mixes and yield issues.

Achieving the exact Saturated Surface Dry (SSD) condition for fine aggregates requires careful drying with warm air and checking with a slump cone test.