Recently, the basic oxygen furnace slag produced in a new steel-making process aiming at energy and resource saving is being supplied as fine particles under 5mm size because it breaks down itself due to its high content of f-CaO. In future, this type of basic oxygen furnace slag is anticipated to replace the conventional basic oxygen furnace slag.
The objective of this study was to investigate the applicability of this powdered basic oxygen furnace slag as a subbase material. Firstly, the changes in physical and chemical properties, the surface texture and the hydrated products of the basic oxygen furnace slag naturally weathered outdoors. were determined by X-ray diffraction, differential thermal analysis (DTA) and SEM-EDXA analysis. Secondly, the strength test, the CBR test and the expansion test of the compacted basic oxygen furnace slag mixtures were carried out in order to clarify the strength characteristics of the powdered basic oxygen furnace slag as a subbase material and the effect of weathering outdoors on reducing its unfavorable self-deterious properties.
The main results obtained are summarized as follows;
(1) The major compounds of the powdered basic oxygen furnace slag were β-C
2S, C
2F, C
2S-C
3P, Wustite and a considerably large amount of f-CaO and Ca(OH)
2.
(2) In the powdered basic oxygen furnace slag naturally weathered outdoors, the hydration of β-C
2S and f-CaO slowly progressed with age, resulting in the formation of C-S-H gel, Ca(OH)
2 and CaCO
3 on the surface of particles.
(3) The powdered basic oxygen furnace slag became a stable material not showing self-deterious property by weathering outdoors for about three months, and thus it can be used as a subbase material.
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