How to Calculate Aggregate Specific Gravity
Comparing an aggregate's density to water's, and why it matters for mix design
What specific gravity means
Specific gravity is a dimensionless ratio of a material's density to the density of water at a reference temperature. An aggregate with a specific gravity of 2.65 is 2.65 times denser than an equal volume of water. Because it's a ratio, it has no units and doesn't change with the sample size.
How it's measured
For coarse aggregate, a common method (such as ASTM C127) involves weighing a saturated surface-dry sample in air and then submerged in water; the difference relates to the volume of water displaced. For fine aggregate, a pycnometer method (such as ASTM C128) is used instead, since a submerged-weight method doesn't work well for sand-sized particles.
Why mix designers need it
Specific gravity converts between an aggregate's weight and its volume, which is essential for concrete and asphalt mix design — proportions are often specified by weight, but the mix's total volume (and therefore yield) depends on each ingredient's actual volume, derived using its specific gravity.
Worked Example
A saturated surface-dry aggregate sample weighs 500 g in air and 310 g submerged in water.
Volume of water displaced (by mass, since water's density ≈ 1 g/cm³): 500 − 310 = 190 g → 190 cm³
Specific gravity = 500 ÷ 190 ≈ 2.63
Related Calculators
Related Guides
From the Blog
Sources
ASTM C127 / C128
Standard Test Methods for Relative Density (Specific Gravity) and Absorption of Coarse / Fine Aggregate.