article posted 04 April 2016
Hans RoggendorfPresenting author: Hans Roggendorf, studied mineralogy and crystallography (crystal growth from glass melts) at
University of Cologne (1972-1980), Germany, investigated condensation reactions in waste gases, glass corrosion and binders at Fraunhofer-Institute for
Silicate Research (1980-1992), Würzburg, Germany, then industry (1992-1995), now professor for nonmetallic-inorganic materials at Martin-Luther-University
Halle-Wittenberg, especially investigating water glass, slag dissolution and binders.
Chemical reactivity of slag glasses from hot metal production as a function of cooling and composition
Melanie Dathe*, Hans Roggendorf*, Volkert Feldrappe** und Andreas Ehrenberg **
*Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Germany
** FEhS-Institute für Baustoff-Forschung e.V., Duisburg, Germany
Slag glasses result from quenching liquid slags arising in metallurgical processes designed to separate metal melt and inorganic components origination from
gangue, coke, burden and refractories. Main components of the slag glasses are CaO, SiO2
, MgO, and Al2
2 is regarded as an important minor component. The structure
of rapidly cooled slags from hot metal production in a blast furnace is pre-dominantly amorphous. Ground slag glasses are used as latent-hydraulic addition to Portland
cement. Slags from industrial production (12 samples) as well as slags chemically modified (18 different com-positions) and granulated in the laboratory were investigated.
Composition and cooling process (8 variations applied to one standard composition) of the laboratory slags were varied systematically. The structure of the slags was
characterized by thermal analysis (glass transition, crystallization) and NMR spectroscopy (29
Si and 27
Al, Fig. 1). The chemical reactivity was characterized via the
chemical durability by applying dynamic corrosion tests to ground slag glasses. Deionised water and 0.01 M Ca(OH)2
solutions were used as leachants. A flow rate of
0.1 l/d, a temperature of 50 °C, a container volume of 60 ml and a surface area of the milled glass powder of 3.5 m² were the main parameters of the corrosion tests.
Fig. 2 shows the corrosion rates of one slag subjected to different cooling processes as a function of the fictive temperature. For surface analysis with scanning
electron microscopy some glass plates with a size of 1.6 x 1.2 x 0.1 cm³ were prepared and corroded at comparable conditions. The reaction progress was measured by
chemical analysis of the leachate on Si and Ca (if applicable). The reaction kinetics usually followed linear time laws and are discussed with respect to glass
composition, granulation process parameters, glass structure, thermodynamics of the dissolution reaction and mortar strength achieved as addition to Portland
cement (Fig. 3).