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

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Abstrakt

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.

OriginalsprogEngelsk
Artikelnummer178926
TidsskriftThermochimica Acta
Vol/bind699
Antal sider10
ISSN0040-6031
DOI
StatusUdgivet - 2021

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