Synthesis of Inorganic Polymers Using a CaO-Al₂O₃-FeO-SiO₂ Slag

Abstract:

The focus of the present paper is to investigate the effect of the activating solution on the structure and mechanical properties of inorganic polymers synthesised from a slag resembling the vitrified residue from a Waste-to-Energy plasma installation. The slag consists of (in wt.%) 22 CaO, 12 Al₂O₃, 34 SiO₂ and 20 Fe₂O₃ and the activation solution was 50:50 mass ratio NaOH and sodium silicate, with the NaOH solution molarities varying from 2 M to 10 M. The synthesised slag was almost completely amorphous due to the rapid cooling, with only traces of magnetite and quartz. The inorganic polymers were prepared by mixing the slag, sand and activation solution. In all cases, heat was generated during sample preparation and its amount increased with the activating solution strength. After 90 days, the compressive strength of the samples activated with 6 M or higher NaOH solutions was similar, approximately 88 MPa. For NaOH activation solutions with molarities lower than 6 M, the compressive strength was lower, both at early as well as late curing times. SEM and EPMA analysis revealed-between undissolved particle remnants-a distinct binder phase, composed of (in wt.%) 18.9±2.5 CaO, 11.5±0.1 Al₂O₃, 40.3±2.1 SiO₂, 15.8±1.2 FeO, 5.1±1.9 Na₂O and 3.7±0.6 MgO. In conclusion, the present study showed that the CaO-Al₂O₃-FeO-SiO₂ vitrified residue could be converted into a stable inorganic polymer having reasonably high mechanical strength, when activated with a mixture of sodium silicate and sodium hydroxide solution with a molarity of at least 4 M.

• Periodical: Advances in Science and Technology (Volume 92)
• Pages: 32-37
• DOI: https://doi.org/10.4028/www.scientific.net/AST.92.32
• Online since: October 2014
• Authors: Lubica Kriskova*, Lieven Machiels, Peter Tom Jones, Bart Blanpain, Yiannis Pontikes
• Keywords: CaO-Al₂O₃-FeO-SiO₂ Slag, Inorganic Polymer

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