Abstract
Today, the decline in soil fertility progress, therefore, special attention paid to the search for new, including non-traditional sources of raw materials that allow cultivating agricultural crops. It is propose to use expanded obsidian as a soil aerator. Obsidian is a volcanic rock, consisting of volcanic glass in which water content does not exceed 1%. A characteristic feature of this stone is the ability to expand under heat treatment. The expansion of obsidian is possible to implement at temperatures of 1050… 1150 °C. It has been shown that due to obsidian expansion it is possible to obtain a light porous filler with an average density of 200… 350 kg/m3, where the heat treatment of 5… 10 mm grains should be performed under temperatures from 1050 to 1150°C, during 3…5 minutes. The mechanical strength of the expanded obsidian is due to the thickness of the internal partitions of the pores and depends on the total porosity. Increased porosity decreases the strength of the expanded obsidian grains as the internal partitions of the pores become thinner. Relatively high mechanical strength develop grains with less porosity, ie lower coefficient of expansion. At the same time, the nature of the external surface of the grain has a significant influence on the mechanical strength. The melted surface,under other equal conditions provides mechanical strength increase of the expanded obsidian.
Highlights
A characteristic feature of this stone is the ability to expand under heat treatment
It has been shown that due to obsidian expansion it is possible to obtain a light porous filler with an average density of 200... 350 kg/m3, where the heat treatment of 5... 10 mm grains should be performed under temperatures from 1050 to 1150oC, during 3...5 minutes
Obsidian is a volcanic rock consisting of volcanic glass in which the water content does not exceed 1%
Summary
Obsidian is a volcanic rock consisting of volcanic glass in which the water content does not exceed 1%. Obsidian expansion up to pyroplastic state is due to the formation of a liquid phase in the mineral melt In this case, the viscosity decreases sharply, the gas phase pressure increases, creating an excess pressure sufficient to overcome the viscosity of the melt and to overcome the surface tension forces. Obsidian expansion process during heat treatment of the material to the pyroplastic state due to the formation of a liquid phase in the mineral melt. In this case, the viscosity decreases, the gas phase pressure increases, creating an excess pressure sufficient to overcome the viscosity of the melt and to overcome the surface tension forces. The gases in the pores during the expansion increase approximately 4... 5 times with the increase of the temperature. [5-11]
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