Volcanic materials for construction purposes in cold regions

Volcanic materials may serve as a natural resource for construction purpose – as light weight aggregate, as building blocks and even (when it comes to the ashes) as pozzolanic material. To be able to benefit from the properties of these materials, especially relating to use in cold regions, knowledge of their thermal properties will be of vital importance. A comprehensive study has been performed for volcanic materials at Kamchatka in East Russia and Iceland. Generally, existing data were received mostly for volcanic solid rocks or for thawed state, but for use in cold regions it is also very important to know the thermal properties in frozen state and the phase composition of water (unfrozen water content). It was observed that thermal conductivity and thermal diffusivity are very low both in thawed and frozen state and these materials therefore can serve as isolation materials. In dry state thermal conductivity is 0.14-0.18 W(m•K) and thermal diffusivity – 0.13-0.16 m2/s. On condition that the density (ρd) and humidity (W) are changing from 0.7 to 1.65 g/sm3 and from 10 to 80 % respectively the thermal conductivity (λ) increases from 0.37 to 1.0 W/(m•K) in a thawed and from 0.41 to 1.27 W/(m•K) in a frozen state. The dependence on humidity degree (Sr) showed that these coefficients also depend on glass composition (andesitic, rhyolitic and basaltic types) and secondary minerals (opal, palagonite and allophane) that occurred after volcanic glass alteration. The higher values were found for volcanic material containing rhyolitic glass and opal, the lowest values for materials with andesitic and basaltic glass as well as with allophane and palagonite. Unfrozen water content also depends on the mineral and chemical compositions. For example, for the first group Ww can change from 0 to 2-3%, for the second group it can vary from 3 to 11% under temperature below -2oC.