Abstract
The object of study is the technology of creation of claydite with a minimal coefficient of thermal conductivity. Most problematic is the lack of methods for determining the optimal technological parameters of thermal treatment of raw materials to obtain claydite with a low coefficient of thermal conductivity. The reason for this is that the existing methods are aimed at creating mullite during roasting of the alumina raw materials, as a substance of sufficient strength. Although, when claydite is used as a thermal insulation filling or as an additive to a concrete mixture, a reduction in the coefficient of thermal conductivity in the formation of the structure of claydite is more significant than the strength value. In the course of research, we created a number of experimental samples of claydite at different initial factors. Fire resistance was determined by comparing the behavior of the examined and standard samples when heated. Bulk thermal conductivity was determined by the thermal conductivity meter ITP-MG4 made by SKB Stroypribor, Russia. Strength of the material was determined by the Rockwell method. To determine the optimal technological parameters for the production of claydite from the specified alumina mixture, we used the method of experiment planning and the optimization of the resulting equation employing the Lagrange method with the Kuhn–Tucker conditions. Based on data received, the technology of obtaining claydite with improved thermal-physical properties is as follows. Clay mixture is dried to humidity of 38 % and the granules are formed (by pressing a grid with a cell of 6×20 mm). Next, the pallet with granules is put into a heating furnace for 15 minutes at 270 °C. After the heating furnace, the granules are discharged into a drum furnace, where they are roasted at temperature 1250 °C for 1.5 hours. The results obtained make it possible to reduce the coefficient of thermal conductivity of claydite by 2.25 times. The applied technique could be used for future studies of samples with different additives, including industrial waste. This in turn will allow a more effective use of available raw materials as well as reduction in the cost of product.
Highlights
We investigated the influence of temperature of thermal treatment Х1, thermal exposure time Х2, and humidity of the starting mixture Х3 on the bulk thermal conductivity Y1 and compressive strength Y2 of claydite
We studied dehydration of material during thermal treatment of alumina and defined two stages of claydite formation with the required thermal-physical characteristics: the stage of pore formation and roasting
We chose a composition of mixture of the starting material and created claydite out of it with the lowest possible coefficient of thermal conductivity
Summary
Claydite is a common material used both as a thermal insulation filling and as a separate filler for concrete mixture. Authors conducted research using the samples of different chemical composition They analyzed physical parameters both of raw materials and of claydite. They demonstrated a porous metal sample, obtained by the addition of claydite. The studies conducted demonstrate a change in humidity and thermal conductivity of materials over time. There is no detailed analysis of the thermal insulation properties of buildings with a «green» roof and a foundation made of a layer of claydite. Authors conducted a detailed study into characteristics of the strength of the samples. Authors demonstrated a change in the shape of granules at different temperatures of roasting the non-carbonate clay without additives and the clay with 3 % of sapropel. The work, did not pay proper attention to the thermal-physical properties of the developed materials
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