Utilization of weathered basic oxygen furnace slag in the production of hydraulic road binders
ABSTRACT This paper deals with the use of a weathered basic oxygen furnace (BOF) slag as a main constituent in hydraulic road binder. The original idea of this study was to associate the BOF slag with ground granulated blast furnace slag (GGBFS). The free lime contained in BOF slag activated the GGBFS. Small amounts of catalyst were added to the mixtures in order to accelerate the setting of this ternary blended binder. Before studying the characteristics and the influence of the proportion of each constituent, the chemical, mineralogical and physical characteristics of BOF slag were analyzed. X-ray diffraction showed that the main minerals present were calcium silicates (βC2S and C3S), dicalcium ferrite (C2F), lime (CaO), a solid solution of magnesium iron oxide (MgOxFeOy), an alumino ferrite calcium phase (C4AF) and, due to the weathering, calcite (CaCO3) and portlandite (Ca(OH)2). The activity of BOF slag in cement-based mortars was evaluated and the results show that BOF slag has little hydraulic activity and apparently no pozzolanic properties. These results were confirmed by XRD on hydrated BOF slag. Only CaO, C3S and C4AF react with water and, as the C3S and C4AF contents were relatively low, the hydraulicity of the BOF slag under study was low. However, BOF slag contains 7% of Ca(OH)2 and, in spite of the weathering, still 5% of CaO. The production of a ternary blended binder containing a mixture of BOF slag, GGBFS and catalyst was a success. The optimization of the binder composition showed that it was possible to produce an HRB10 (the compressive strength of standardized mortars higher than 10MPa at 56 days) by mixing 52.5% of GGBFS, 42.5% of BOF slag and 5% of catalyst. Moreover, the stability study showed that there was no problem of expansion with such a binder.
Article: Use of steelworks slag in Europe[show abstract] [hide abstract]
ABSTRACT: At any time the steel industry has been a pioneer for recycling. Recycling of scrap and the early use of blast furnace slag products on a high level are only two excellent examples. As a result of a comprehensive research during recent years in all European countries the use of steelworks slag could be increased. In any application of BOS slag the technological and environmental properties are of fundamental importance. It can be shown that these properties of steelworks slag makes it suitable in many kinds of application in the construction industry, as fertiliser and for metallurgical use.Waste Management. 01/1996;
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ABSTRACT: The slags from blast furnace (iron making ) and converter (steel making) after magnetic separation are mixed with limestone of six different compositions. The ground materials are fired in a pilot plant scale rotary kiln to 1350 °C for 1 h. The clinker is cooled, crushed, mixed with 3% gypsum, and ground to fineness of more than 3300 cm2/g. Initial and final setting times, consistency of standard paste, soundness, free CaO, and compressive and fractural strengths after 3, 7, and 28 days are measured. Samples with higher lime saturation factor developed higher C3S content and better mechanical properties. Blending 10% extra iron slag to a cement composed of 49% iron slag, 43% calcined lime, and 8% steel slag kept the compressive strength of concrete above standard values for type I ordinary Portand cement.Cement and Concrete Research. 01/1999;
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ABSTRACT: At all stages of pavement life, the highway surface should have some sort of roughness to facilitate friction between car wheels and pavement surface. Skid resistance is a measure of the resistance of pavement surface to sliding or skidding of the vehicle. It is a relationship between the vertical force and the horizontal force developed as a tire slides along the pavement surface. The texture of the pavement surface and its ability to resist the polishing effect of traffic is of prime importance in providing skidding resistance. Polishing of the aggregate is the reduction in microtexture, resulting in the smoothing and rounding of exposed aggregates. This process is caused by particle wear on a microscopic scale. It is a common fact that the lower the skid resistance value, the higher the percentage of the traffic accidents, especially during the wet seasons. Having a low skid resistance value at an asphalt concrete surface might be attributed to one or more of the following reasons: (1) use of higher asphalt content than recommended by the mix design procedure, (2) the Marshall mix design procedure itself, (3) used aggregate gradation, and (4) aggregate quality. To evaluate these factors, a comparative study was performed to find the British Pendulum Skid Resistance Number for a number of mixes. These mixes included, an asphalt concrete mix using local aggregate at the optimum Marshall asphalt content, mixes with 0.5% and 1.0% asphalt contents higher than Marshall optimum asphalt content, a mix designed using Superpave design procedure, a mix with steel slag to replace 30% of limestone aggregate, and a mix with stone matrix aggregate gradation. It was found that the mix with 30% slag has the highest skid number followed by Superpave, SMA, and Marshall mixes, respectively. It was also observed that increasing the asphalt content above the optimal asphalt content value decreases the skid resistance of these mixes.Building and Environment. 01/2007;