# Bulk density

The bulk density , also known as the apparent or geometric density or volume weight , is the density of a porous solid based on the volume including the pore spaces:

${\ displaystyle \ rho _ {\ text {raw}} = {\ frac {m} {V _ {\ text {fixed}} + V _ {\ text {por}}}}}$ The counterpart to the bulk density is the true density . The true density and gross density of un porous bodies are the same:

${\ displaystyle V _ {\ text {por}} = 0 \ Rightarrow \ rho _ {\ text {raw}} = \ rho _ {\ text {pure}}}$ The quotient of raw and true density is the relative density . Their difference to 1 (or 100%) is the total porosity (the sum of open and closed porosity).

Connections:

• In the case of building materials , an increasing bulk density usually has a positive effect on sound insulation and a negative effect on thermal insulation .
• In the case of material that is homogeneous except for the cavities ( foams and other foam materials ), the bulk density can be determined by comparing the volumes before and after foaming.
• In the case of mattresses , the "volume weight", which is often mentioned as the main quality feature, refers to the mass of the processed raw material (e.g. plastic or latex). In other words, a finished mattress with a higher density (with the same dimensions) has a lower air or pore volume, a higher (raw) density and a lower porosity than a comparative mattress.

## Density in construction

In DIN 12697 on testing asphalt, the gross density ( maximum density ) denotes the mass of asphalt without air pores, the counterpart of the above definition. The mass of a test specimen, based on the volume including air pores, is referred to here as the volume density .