Abstract
The purpose of this study was to improve the recycling rate of industrial wastes by investigating the bloating mechanism of artificial lightweight aggregate depending on the ramping rate and time, which is a dynamic parameter in the production of artificial lightweight aggregate. In this study, coal bottom ash and dredged soil at a weight ratio of 1 : 1 from a domestic power plant were used as raw materials. The artificial lightweight aggregates were formed by using an extruder and pelletizer (φ = 10 mm) and sintered by rapid sintering, 2-step firing, and normal sintering method. The physical properties of the aggregates such as bulk density, water absorption ratio, and microstructure of cross section are investigated with the sintering time and temperature. As the result of bloating and trapping mechanism, black core could be inhibited as the firing time increased at the temperature before surface formation. As a result of firing schedule graphs using least square method, it was possible to manufacture artificial lightweight aggregate with micropores, specific gravity of 1.1, and absorption rate of 3% at a heating rate of 27°c/min or less.
Highlights
As a result of the rapid national economic and industrial growth, the amount of industrial waste according to such development is continuously increasing
Materials. e raw materials used in this study were a mixture of coal bottom ash (B/A), which was discharged after burning bituminous coal in Y thermal power plant, and dredged soil (D/S) in 1 : 1 ratio by weight. e raw material was pulverized to less than 200 mesh using a pin mill. e chemical composition of the pulverized raw material was analyzed using XRF (ZSR-100e, Rigaku, Tokyo, Japan). e phase of the raw material was analyzed by XRD (Miniflexll, Rigaku, Tokyo, Japan)
In order to produce artificial lightweight aggregate, the dredged soil, which is inorganic plasticizer, and coal bottom ash were mixed at a weight ratio of 1 : 1, and the mixture was pulverized to less than 200 mesh using a pin mill (TOP, Korea Mechanical Engineering, Changwon, Korea). e pulverized mixture was set to a moisture content of 20%, and artificial lightweight aggregate was formed into a size of about 10 mm using an extruder (GRN05, VANHO, Chilgok, Korea). e discharged product was rotated for 5 minutes at 40 rpm and 50° using a pelletizer (WPP 700, Woongbi Machinery, Cheonan, Korea), and resulting aggregate was dried at 105°C for 24 hours using a dryer
Summary
As a result of the rapid national economic and industrial growth, the amount of industrial waste according to such development is continuously increasing. In the case of bottom ash, only a part of it is used as a construction fill materials, and when it is used as an aggregate in concrete, there is a limitation in recycling for the quality problems resulting from the workability, which is due to the interlocking phenomenon and management of water content by surface pore [4]. Lightweight aggregate is lightened by bloating when it is fired, and it requires generation of gas for Advances in Materials Science and Engineering foaming and surface which can collect the formed gas [19, 20]. Unlike the artificial lightweight aggregates that are manufactured using the existing natural raw materials with low refractoriness, for lightening of the weight, sintering at a high temperature is necessary when artificial lightweight aggregate is produced using recycled resources with high refractivity. The rate of control of the two reactions determines the bloating behavior of the artificial lightweight aggregate
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