STUDIES OF EARLY HYDRATION REACTIONS OF PORTLAND CEMENT BY X -RAY DIFFRACTION

MONITORING BY X-RAY DIFFRACTION OF HYDRATION OF TRICALCIUM ALUMINATE IN PASTES CONTAINING CALCIUM HYDROXIDE AND GYPSUM HAS DEMONSTRATED SUCCESSIVE FORMATION OF THE HIGH-SULFATE FORM OF CALCIUM SULFOALUMINATE HYDRATE /ETTRINGITE/, THE LOW -SULFATED HYDRATE AND TETRACALCIUM ALUMINATE HYDRATE. THESE REACTIONS AND EFFECTS OF VARIOUS FACTORS ON THEM CORRESPOND VERY CLOSELY TO THE EARLY HYDRATION BEHAVIOR OF C3A IN PORTLAND CEMENT. DIFFRACTION STUDIES OF HYDRATING SINTERED TRICALCIUM ALUMINATE SLABS HAVE DEMONSTRATED THE RETARDING EFFECT OF THE INITIALLY FORMED ETTRINGITE FILM. X-RAY AND DILATOMETER STUDIES HAVE SHOWN THAT THE HYDRATING C3A PASTES UNDERGO LARGE INCREASES IN VOLUME BECAUSE OF A TENDENCY TO IMBIBE LARGE QUANTITIES OF WATER. THE INDIVIDUAL EFFECTS OF OTHER PORTLAND CEMENT CONSTITUENTS ON THESE HYDRATION REACTIONS HAVE BEEN INVESTIGATED. A STUDY OF HYDRATION OF COMBINATIONS OF THE VARIOUS CONSTITUENTS HAS LED TO A FAIRLY COMPLETE PICTURE OF THE EARLY HYDRATION REACTIONS OF PORTLAND CEMENT. EXAMINATION OF A FEW WELL-KNOWN ACCELERATING AND RETARDING MATERIALS HAS SHOWN THEM TO AFFECT PRIMARILY THE HYDRATION RATE OF C3S. THEY MAY AFFECT THE RATES BUT NOT THE NATURE OF THE EARLY C3A REACTIMONS. RETARDERS CAN PRODUCE A LARGE INITIAL ACCELERATION OF C3A HYDRATION. WHEN CONSIDERED IN RELATION TO THE STATE OF THE CALCIUM SULFATE IN THE CEMENT, THIS PREVIOUSLY UNRECOGNIZED EFFECT CAN ACCOUNT FOR MANY INSTANCES OF ABNORMAL SETTING OF CONCRETE. OPTIMUM SO3 CONTENT IS CHARACTERIZED BY GYPSUM DEPLETION AT 18 TO 24 HR AFTER GAGING. HIGHER SO3 CONTENTS CAUSE WATER IMBIBITION TO PRODUCE EXCESSIVE EXPANSION AND LOWERED STRENGTH. THIS WATER IMBIBITION IS A MAJOR FACTOR IN THE BEHAVIOR OF SHRINKAGE- COMPENSATING AND EXPANSIVE CEMENTS. /AUTHOR/

• Record URL:
  • http://onlinepubs.trb.org/Onlinepubs/hrr/1964/62/62-007.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.
• Authors:
  • Seligmann, Paul
  • Greening, Nathan R
• Publication Date: 1964

Media Info

• Media Type: Print
• Features: Appendices; Figures; References; Tables;
• Pagination: pp 80-105
• Monograph Title: Research on aggregate, cement, concrete and epoxy bonding
• Serial:
  • Highway Research Record
  • Issue Number: 62
  • Publisher: Highway Research Board

Subject/Index Terms

• TRT Terms: Accelerating agents; Aluminates; Calcium compounds; Concrete construction; Diffraction; Ettringite; Expansion; Extensometers; Hydration; Portland cement; Retarders (Chemistry); X rays
• Uncontrolled Terms: X-ray diffraction
• Old TRIS Terms: Reaction
• Subject Areas: Geotechnology; Highways; Materials;

Filing Info

• Accession Number: 00211954
• Record Type: Publication
• Files: TRIS, TRB
• Created Date: Mar 16 1994 12:00AM