ADSORPTION OF ORGANIC VAPORS IN RELATION TO THE PORE STRUCTURE OF HARDENED PORTLAND CEMENT PASTES
INVESTIGATIONS OF HARDENED PASTES OF PORTLAND CEMENT WERE PERFORMED SIMILAR TO THE INVESTIGATIONS OF THE PORE STRUCTURES AND SURFACE AREAS BY NITROGEN ADSORPTION. ADSORPTION-DESORPTION ISOTHERMS WERE DETERMINED USING ORGANIC VAPORS OF DIFFERENT MOLECULAR AREAS AND POLARITIES. THE VAPORS USED WERE CYCLOHEXANE, ISOPROPANOL AND METHANOL. THE SURFACE AREAS AND PORE VOLUMES ACCESSIBLE TO EACH WERE OBTAINED AND COMPARED TO THOSE OBTAINED WITH NITROGEN AND WATER VAPOR. THE RESULTS OBTAINED CAN BE EXPLAINED BY VISUALIZING THE MICROSTRUCTURE OF THE PASTE AS CONSISTING OF AGGREGATED MASSES OF THE BASIC STRUCTURAL UNITS, MAINLY TOBERMORITE GEL SHEETS, WITH THE MASSES SEPARATED BY PORES WITHIN THE AGGREGATED MASSES. THE PORE SYSTEM WITHIN THESE MASSES IS DESIGNATED THE INTERNAL PORE SYSTEM, AND BETWEEN THE MASSES THE EXTERNAL PORE SYSTEM, THE MAIN CONCLUSIONS WERE AS FOLLOWS' /1/ CYCLOHEXANE AND ISOPROPANOL MEASURE ONLY THE EXTERNAL PORE SYSTEM, WHEREAS METHANOL AND NITROGEN CAN PARTLY BE ADMITTED TO THE INTERNAL PORE SYSTEM. WATER SEEMS TO MEASURE THE ENTIRE PORE STRUCTURE OF THE PASTE, /2/ THE EXTERNAL PORE SYSTEM CONTAINS BOTH S /SMALL/ AND L /LARGE/ PORES. THERE IS EVIDENCE THAT THE INTERNAL PORE SYSTEM ALSO CONTAINS BOTH S AND L PORES. CYCLOHEXANE AND ISOPROPANOL ARE EXCLUDED FROM THE INTERNAL PORE SYSTEM BECAUSE THE AGGREGATED MASSES HAVE NARROW ENTRY WAYS TO THE INTERNAL PORE SYSTEM, /3/ STUDY OF THE HYDRAULIC RADII SHOWS THAT THE ENTRY WAYS TO THE PORES HAVE A SIZE DISTRIBUTION, AND /4/ THE SIZE OF THE ADSORBATE MOLECULE DETERMINES ITS ABILITY TO PENETRATE INTO SMALL PORES. POLARITY OF THE MOLECULES PLAYS A MINOR ROLE AT LOW RELATIVE VAPOR PRESSURES, BUT AT HIGH PRESSURES IT CAUSES EXPANSION OF THE PASTES. /AUTHOR/
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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
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Corporate Authors:
Highway Research Board (HRB)
Washington, DC -
Authors:
- Mikhail, Raouf Sh
- Selim, Suzy A
- Publication Date: 1966
Media Info
- Media Type: Print
- Features: Figures; References; Tables;
- Pagination: pp 123-134
- Monograph Title: Symposium on structure of Portland cement paste and concrete
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Serial:
- Highway Research Board Special Report
- Issue Number: 90
- Publisher: Highway Research Board
Subject/Index Terms
- TRT Terms: Absorption; Concrete hardening; Hardness; Isotherms; Methanol; Molecules; Nitrogen; Pastes; Pore space; Pore water; Portland cement; Surfaces; Vapor pressure
- Uncontrolled Terms: Isopropanol; Surface area
- Old TRIS Terms: Cyclohexane; Organic vapors; Polarity
- Subject Areas: Highways; Materials;
Filing Info
- Accession Number: 00212285
- Record Type: Publication
- Files: TRIS, TRB
- Created Date: Dec 12 1994 12:00AM