Vermiculite is formed through the disintegration of mica, which liberates lime and takes up water. When vermiculite is heated to 800-1100 °C, it divides into thin strips. These release water, curl up like snakes and swell to become a light porous mass which can be used as an independent loose insulation or as an aggregate in a lightweight concrete, e.g. in the proportions 6:1 vermiculite to Portland cement.
Other mineral binders can be used. Prefabricated slabs are made in varying thicknesses, from 15 to 100 mm.
Vermiculite easily absorbs large amounts of moisture, and substantially more than untreated perlite. It is therefore particularly useful for insulation of high temperature equipment. As normal wall insulation, it has a tendency to settle a great deal. This can be solved by applying compression up to 50%, using a coarser form of the material.
The environmental picture is approximately the same as for perlite, except for a few extraction sites where there have been shown to be significant amounts of asbestos (Curwell et al., 2002).
Was this article helpful?