Applicability of Basic Oxygen Furnace Slag as a Concrete Aggregate


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Title: Applicability of Basic Oxygen Furnace Slag as a Concrete Aggregate

Author(s): Mitsunori Kawamura, Torii, Shigemasa Hasaba, Nobuhiro Nicho, and Kiyotoshi Oda

Publication: Special Publication

Volume: 79


Appears on pages(s): 1123-1142

Keywords: aggregate gradation; aggregates; compressive strength; sands; slags; soundness; weathering; workability; x-ray diffraction.

Date: 5/1/1983

Little basic oxygen slag is used as a portland cement concrete aggregate because of its unsoundness in concrete. However, soundness of basic oxygen furnace slag in concrete appears to largely depend upon the mineralogical and chemical compositions of the slag. Several experiments concerning workability, compressive strength and dimensional stability of concrete made with basic oxygen furnace slag were conducted for investigating the possibility of the use of basic oxygen furnace slag as a concrete aggregate. The concrete made with weathered slag showed a much higher slump for a given mix proportion than natural aggregate concrete and the concrete prepared using unweathered slag. The longer the periods during which the slag used wasplaced outdoors, the lower the compressive strength of the slag concrete. The changes in the mineralogical and chemical compositions and the surface texture of basic oxygen furnace slag particles were determined by X-ray diffraction, differential thermal analysis, SEM and EDAX. The results of these experiments show that reduction in compressive strength and high slumps in the concrete made with the weathered slag aggregates arise from slow hydration of C2S and C2F on and/or near the surface of basic oxygen furnace slag during weathering. It may be concluded that basic oxygen furnace slag can be used as a concrete aggregate if the grading of fine slag aggregates coarsened by its slow hydration is improved by adding river sand so as to obtain a workable concrete.