2018 Volume 72 Issue 1 Pages 438-445
Volcanic ejecta comprises crystal mineral and pumice, sometimes weathering clay fraction in their natural condition. By focusing on the differences of physical properties between these components, high purity volcanic glass was manufactured by sorting out particles less than 2.4g/cm3. This research shows the deference between volcanic glass powder and clay fraction which are manufactured through dry gravity classification and pulverization from Ito shirasu, one of the biggest pyroclastic flow deposit, which includes crystal mineral, pumice, and so on. Adsorbed amount of Methylene blue and chemical admixture by clay fraction is larger than that by volcanic glass powder, and mortar flow value with clay fraction decrease. And also Chemical composition, thermal analysis, and XRD showed that weathering proceeds from the surface of the particle. Recovery rate of clay fraction is only two percent through the method, but pulverization makes its properties as mineral admixture worse. That is because concentration of surface weathering layer. These results demonstrate dry gravity concentration is technically effective.
