Abstract
In the production of crushed stone, lithoidal pumice and perlite sand, it is advisable to separate and segregate the obsidian. Wherein, the separated obsidian is converted into production waste. By the expansion of obsidian it is possible to obtain an ultralight large grain porous material and thereby solve environmental issues - to dispose of waste products. The expansion of volcanic glass (obsidian) occurs due to gases, primary (magmatic) and secondary (hydraulic) water, which is located in the pores. During the expansion, under heat treatment, the gases expand about 4 ... 5 times in the pores, which contributes the expansion. Expanded obsidian can be used as a filler for lightweight concrete. Obsidian is expanded at temperatures of 1050-115°C. The lowest average density of 200 - 350 kg / m3 (in a piece) is obtained by heat treatment of obsidian with a particle size of 5 to 20 mm for a duration of 3-10 minutes. Depending on the requirements for lightweight aggregates, by adjusting the firing temperature and duration, it is possible to obtain expanded obsidian with the necessary physical and mechanical properties. It is revealed that more durable concretes are obtained with cement consumption of 350 ... 380 kg. Depending on the average density of lightweight concrete 400 .. 1350 kg/m3, the compressive strength is 0.2 ... 16,9 MPa. Light monolithic products with improved characteristics of heat resistance and thermistance, having an average density of 180-200 kg/m3, compressive strength of 1.2–1.5 MPa, frost resistance of 25 cycles, after which the strength changes to 1.0–1.3 MPa, heat resistance to 800–850°C, and thermistance to 600–650°C. By the thermal conductivity coefficient determination it was possible to reveal that in the temperature range of 20-60°C, the thermal conductivity coefficient changes by 0.002 W/mK, i.e. from 0.044 to 0.046 w/mK. Thus, the obtained monolithic blocks can be very successfully used as heat-insulating materials, which will retain their properties throughout the operation of the facilities. The requirements for mechanical strength and decorative properties for sound-absorbing materials compared to thermal insulating materials are higher, since they are used for internal linings. Thus, the obtained monolithic blocks can be very successfully used as heat-insulating materials, which will retain their properties throughout the operation of the facilities.
Highlights
For the development of mineral raw material production with the high content of the useful components, the industry is forced to switch to the use of poor and unconventional raw materials
The studies have revealed that for lightweight concretes which are based on ultralight large grain aggregate, the particle size limit is 20 mm, while the concrete is more homogeneous compared to concrete, which uses larger particles
By adjusting the degree of intergranular voids, it is possible to obtain lightweight concrete based on expanded obsidian with a certain strength and medium density
Summary
For the development of mineral raw material production with the high content of the useful components, the industry is forced to switch to the use of poor and unconventional raw materials. Expansion of obsidian will allow to obtain ultralight large grain porous material and thereby solve environmental issues - to recycle production waste. Water absorption of lightweight aggregate is associated with the expansion coefficient, surface and particle size.
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