Density of Aggregate - Bulk and Relative Density

Density is an important parameter for aggregate. For aggregates, density is determined by multiplying the relative density (specific gravity) of the aggregate times the density of water.

Bulk Density of Aggregate [1]

The bulk density or unit weight of an aggregate is the mass or weight of the aggregate that required to fill a container of a specified unit volume.

Bulk Density = ^Mass/_volume

Key Features:

• If the volume is unit then, Bulk Density= Mass.
• Unit in kg/m³ or lb./ft³.
• In this definition, the volume is that contains both the aggregates and the voids between aggregates particles. 
• The approximate bulk density of aggregate that is commonly used in normal-weight concrete is between 1200-1750 kg/m³ (75-110 lb./ft³). 
• Here, the Standard test method for determining the bulk density of aggregates is given in ASTM C 29 (AASHTO T 19). ^[2]

Relative Density of Aggregate [1]

The relative density (specific gravity) of an aggregate is the ratio of its mass to the mass of an equal volume of water.

Relative Density = ^{Mass of the Aggregate}/_{Mass of equal volume of water}

Key Features:

• Most aggregates have a relative density between 2.4-2.9 with a corresponding particle (mass) density of 2400-2900 kg/m³ (150-181 lb./ft³).
• Here, for coarse aggregates, the standard test method has been explained in ASTM C 127(AASHTO) and for fine aggregates, the standard test method has been explained in ASTM C 128 (AASHTO). ^[3] 
• The relative density of an aggregate can be determined on an oven-dry basis or a saturated surface-dry (SSD) basis.