5.13 : 骨材の比重

The specific gravity of aggregate is the ratio of the density of aggregates to the density of distilled water at a given temperature.

The density of aggregate depends on its pores being permeable or impermeable to water, and based on this, the specific gravity of aggregates is differentiated into three types.

Bulk or gross specific gravity considers the density of aggregates as the ratio of the mass of aggregates in the saturated surface-dry state to the total volume of aggregates including solids and voids.

Meanwhile, apparent specific gravity specifies the density of aggregates as the ratio of the dry mass of aggregates to the volume of aggregates, including only the impermeable voids.

 Lastly, absolute specific gravity determines the density of aggregates as the ratio of the dry mass of aggregates to the volume of aggregates, excluding all the voids.

The specific gravity of fine aggregates is measured using a pycnometer, and coarse aggregates are measured using the wire-basket method.

Generally, the apparent specific gravity of natural aggregates ranges from 2.6 to 2.7.