Some Properties of Shirasu as a Siliceous Material for Autoclaved Concrete

　“SHIRASU”,which mainly consists of volcanic ash and pumice colored generally white-grey, is defined as a substance which erupted from the Volcano Aira and Ata from the end of the Early Tertiary to the Quaternary periods of geologic time and has formed thich strata of pumice flow and pumice fall, and their second sedimentary strata, covering a large area of southern Kyushu in Japan. Its reserves are estimated about 70 billion m³, equivalent to 90 billion tons. On the whole, SHIRASU consiste of 52～78% of volcanic glass, 20～45% of plagioclase containing quartz and small amounts of hypersthene, magnetite, augite and apatite. Since its　SiO₂ content is about 70%, SHIRASU is expected to be used as a raw material for autoclaved lightweight concrete in place of silica sand.
　In this experiment, some properties of SHIRASU as a siliceous material for autoclaved concrete, including the effects of its mineral components, i. e. volcanic glass and plagioclase, on the compressive strength and the reactivity, were investigated.