Contribution to the Structure of BOF-Slags and its Influence on Their Volume Stability

Abstract

AbstractAbstractUtilizing steelmaking slags as a material for road construction requires sufficient volume stability, which can be jeopardized by the hydration of free lime, For this reason a detailed investigation was carried out on the effect of free lime content and porosity on volume stability. It was shown that the free lime particles can be present as residual free lime and as lime precipitated during solidification. Both kinds of free lime can be further subdivided into grainy and spongy residual free lime and into free lime precipitated on C2F-grain boundaries, precipitated within C3S-crystals and by decomposition of C3S. It has been found that all different kinds can react with H2O forming Ca(OH)2. Water or water vapour reaches the lime particles via cracks, crevices and channels. Testing the volume stability was performed both on bituminous bound and unbound slag samples. At low free lime contents higher porosities are permissible than at high free lime contents. From the results a correlation between volume stability, porosity, and free lime content was developed. Finally, possibilities for improving the volume stability of steelmaking slags were discussed.