Preparation and thermal properties of commercial vermiculite bonded with potassium silicate

Rasmus Rosenlund Petersen, Johan Frederik Schou Christensen, N.T. Jørgensen, S. Gustafson, L.A. Lindbjerg, Yuanzheng Yue

Research output: Contribution to journalJournal articlepeer-review

Abstract

Expanded vermiculite bonded with potassium silicate finds use as high-temperature insulation boards. The thermal properties of the vermiculite boards are critical for their applications and expected lifetime. This work reports on the processing and thermal properties of vermiculite boards (400–600 kg m−3) prepared from three different commercial vermiculite sources. Commercial vermiculite is first expanded through flash-heating, then mixed with potassium silicate and then finally pressed to boards. The untreated- and expanded vermiculite and the boards are studied with X-ray diffraction, differential scanning calorimetry, thermogravimetry, heating microscope and electron microscope. The expansion process affects the ability of the expanded vermiculite to reabsorb moisture and the ability is dependent on vermiculite source. The vermiculite boards undergoes several physical-chemical transitions at elevated temperatures. Water from both clay minerals and binder is lost at <250 °C. At 800–1200 °C, the dehydroxylation of clay minerals first occurs, then the boards shrink, and forsterite (Mg2SiO4) and leucite (KAlSi2O6) crystallise subsequently. At 1200–1420 °C, the leucite melts and the boards shrink again. The crystallisation- and melting temperatures depend on the vermiculite source. These findings provide practical guidelines for processing vermiculite into lightweight boards.

Original languageEnglish
Article number178926
JournalThermochimica Acta
Volume699
Number of pages10
ISSN0040-6031
DOIs
Publication statusPublished - 2021

Keywords

  • Crystallisation
  • Dehydration
  • Exfoliation
  • Potassium silicate
  • Shrinkage
  • Vermiculite

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