THERMAL DECOMPOSITION OF 14 A TOBERMORITE FROM CRESTMORE

THE THERMAL DECOMPOSITION OF 14 A TOBERMORITE FROM CRESTMORE HAS BEEN STUDIED USING WEIGHT AND CO2 LOSS CURVES, X-RAY FIBER ROTATION PHOTOGRAPHS AND INFRARED ADSORPTION SPECTRA. THE INITIAL MINERAL HAS THE APPROXIMATE COMPOSITION 6CAO. 6SIO2. 9H20 WITH SMALL AMOUNTS OF CO2 AND B203. PART OF THE WATER IS PRESENT IN MOLECULAR FORM, AND SIOH GROUPS MAY ALSO BE PRESENT. THIS IS COMPATIBLE WITH THE IDEALIZED CONSTITUTIONAL FORMULA CA5SI6OL8H2. 8H2. AT 55 C, THERE IS A SHARP CHANGE TO 11.3 A TOBERMORITE, CA5SI6OL8HA. 4H20. THE 11.3 A TOBERMORITE LOSES MOST OF ITS WATER GRADUALLY, AT 55 TO 200 C, APPARENTLY WITHOUT UNDERGOING FUNDAMENTAL CHANGE IN STRUCTURE. AT 200 TO 450 C, A 9.35 A TOBERMORITE IS FORMED. THIS HAS THE APPROXIMATE COMPOSITION CA5SI6OL8H2. AT 450 TO 650 C, MOST OF THE REMAINING WATER IS LOST, AS WELL AS THE CO2. THIS PROCESS APPEARS TO BE A GRADUAL ONE, IN WHICH SOME ESSENTIAL FEATURES OF THE STRUCTURE ARE RETAINED, THE LAYER THICKNESS INCREASES TO 9.7 A. THE PROCESS MAY OCCUR THROUGH CONDENSATION BETWEEN ADJACENT SIOH GROUPS, AS SUGGESTED PREVIOUSLY. AT 730 TO 775 C A WOLLASTONITE-LIKE INTERMEDIATE PHASE IS FORMED, WHICH AT 850 TO 900 C GIVES PLACE TO WOLLASTONITE ITSELF. IFRARED ADSORPTION SPECTRA ARE GIVEN FOR EACH OF THE MAIN STAGES. THE THERMAL BEHAVIOR OF THE CRESTMORE TOBERMORITE SEEMS TO BE ESSENTIALLY SIMILAR TO THAT OF THE BALLYCRAIGY AND SOME SYNTHETIC SPECIMENS, BUT THE CRYSTALLIZATION OF WALLASTONITE IS MORE GRADUAL. THIS IS PERHAPS DUE TO THE PRESENCE OF BORATE IN THE CRESTMORE MINERAL. /AUTHOR/

• Record URL:
  • http://onlinepubs.trb.org/Onlinepubs/sr/sr90/90-025.pdf
• Supplemental Notes:
  • Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
• Corporate Authors:

  Highway Research Board (HRB)

  Washington, DC   
• Authors:
  • Farmer, V C
  • Jeevartnam, J
  • Speakman, K
• Publication Date: 1966

Media Info

• Features: Figures; References; Tables;
• Pagination: pp 291-299
• Monograph Title: Symposium on structure of Portland cement paste and concrete
• Serial:
  • Highway Research Board Special Report
  • Issue Number: 90
  • Publisher: Highway Research Board

Subject/Index Terms

• TRT Terms: Absorption spectra; Carbon dioxide; Condensation; Decomposition; Fiber optics; Infrared analysis; Photography; Thermal properties; Tobermorite; Water; Weight; X ray analysis
• Old TRIS Terms: Borates; Wollastonite
• Subject Areas: Highways; Materials;

Filing Info

• Accession Number: 00212289
• Record Type: Publication
• Files: TRIS, TRB
• Created Date: Dec 22 1994 12:00AM