As per IS : 2386 (part – III) – 1963, the following formula of aggregate is given for : (Net weight of aggregate in kg) / (Capacity of container in litre)
Correct Answer: A. Bulk Density
📚 Detailed Explanation: Bulk Density Formula per IS 2386 (Part III)
IS 2386 (Part III) : 1963 covers the test methods for specific gravity, density, voids, absorption and bulking of aggregates. The bulk density (also called unit weight) is defined as the mass of aggregate needed to fill a container of unit volume, including the air voids between particles.
Why A (Bulk Density) is correct: The formula Mass (kg) / Volume of container (litres) gives the bulk density in kg/litre (numerically equivalent to g/cm³ or t/m³). This is fundamentally different from specific gravity, which uses the true (solid) volume of material and excludes inter-particle voids. Specific gravity > bulk density for the same aggregate.
Key Aggregate Density Terms
| Property | Formula | Includes voids? |
|---|---|---|
| Bulk Density | Mass (kg) / Container volume (litre) | Yes — includes inter-particle air |
| Specific Gravity | Mass in air / (Mass in air − Mass in water) | No — solid volume only |
| Apparent Specific Gravity | Uses oven-dry mass and submerged volume | Excludes permeable pores |
Key Concepts for Students
- Typical bulk density for normal aggregate is 1.4–1.7 kg/litre; specific gravity is 2.6–2.9.
- Compacted vs. loose bulk density: IS 2386 (Part III) tests both; compacted BD is higher and used for mix design volume calculations.
- Angularity number is derived from bulk density: it reflects the % void content in excess of 33% for a standard rounded aggregate.