Glass - Back to the Future!

Presenting Author:
Hans Roggendorf

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 Al2O32 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 (29Si and 27Al, 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).