Porosity-density relations in stone and brick materials

The open porosity of a specimen of stone or brick material is often measured using a gravimetric method based on Archimedes' principle. This widely used technique also allows both the bulk density and the solid density of the specimen to be determined, although the solid density is not often reported. We discuss the relation between the porosity and density, both for single specimens and for groups of specimens of similar materials, using for illustration data on limestones, sandstones and fired-clay bricks. The significance of the solid density can be overlooked but it is informative both as a material property and as a method of identifying errors in data. We emphasize how the solid density depends on mineralogy and on closed porosity.