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EFFECTS OF SORBED WATER ON DIMENSION, COMPRESSIVE STRENGTH AND SWELLING PRESSURE OF HARDENED CEMENT PASTE

EXPERIMENTAL WORK DEALING WITH THE INTERACTION OF WATER AND SOLID IN THE POWERS MODEL OF HARDENED CEMENT PASTE IS PRESENTED IN THREE SECTIONS' /1/ OBSERVATION OF SHRINKAGE, SWELLING AND GAIN OR LOSS OF MOISTURE FOR SPECIMENS BROUGHT TO EQUILIBRIUM AT VARIOUS VALUES OF THE AMBIENT RELATIVE HUMIDITY, /2/ DIRECT MEASUREMENT OF SWELLING PRESSURE, AND /3/ VARIATION OF CUBE STRENGTH WITH THE QUANTITY OF EVAPORABLE WATER. THE RESULTS SUPPORT THE VIEW THAT SHRINKAGE STRAINS MAY ON THE FIRST DESORPTION CYCLE BE REPRESENTED BY A DISCONTINUOUS FUNCTION OF HYDROSTATIC STRESS CALCULATED BY MEANS OF THE KELVIN EQUATION. THE FUNCTION CONSISTS OF TWO NEARLY LINEAR PORTIONS, ONE ASSOCIATED WITH THE ACTION OF FILM PRESSURE TOGETHER WITH HYDROSTATIC TENSION, AND THE OTHER WITH FILM PRESSURE ALONE. AT THE START OF DRYING THE SHRINKAGE IS PREDOMINANTLY DUE TO HYDROSTATIC TENSION WHICH, ACCORDING TO POWERS, IS EFFECTIVE OVER THE WHOLE SURFACE AREA OF THE SOLID. AS THE EQUILIBRIUM RELATIVE HUMIDITY IN THE PORES IS REDUCED BELOW ABOUT 45 PERCENT, THE HYDROSTATIC TENSION EXCEEDS THE FRACTURE STRENGTH OF WATER AND FURTHER SHRINKAGE IS ASSOCIATED WITH DIMINUTION OF FILM PRESSURE AND ELASTIC RECOVERY OF THE SOLID. THE FUNCTIONS RELATING SWELLING AND SHRINKAGE STRAINS WITH CHANGE IN SURFACE ENERGY CALCULATED ACCORDING TO THE GIBBS EQUATION ARE GENERALLY SIGMOIDOL IN SHAPE, BUT ARE NEARLY LINEAR ON ADSORPTION FROM THE OVEN DRY CONDITION. THE EXTERNAL MECHANICAL FORCE NECESSARY TO PREVENT SWELLING WAS MEASURED AND EQUATED TO THE STRESS IN PORE WATER CALCULATED ACCORDING TO THE KELVIN EQUATION MULTIPLIED BY AN EFFECTIVE AREA FACTOR. IT WAS FOUND THAT VARIATIONS IN CUBE STRENGTH WITH PORE WATER CONTENT COULD BE EXPRESSED AS A LINEAR FUNCTION OF THE PRODUCT OF HYDROSTATIC STRESS ACCORDING TO THE KELVIN EQUATION AND THE APPARENT EFFECTIVE AREA. ATTEMPTS TO REMOVE THE DISCONTINUITY IN SHRINKAGE STRAIN VS HYDROSTATIC STRESS CURVES USING EFFECTIVE AREA FACTORS OBTAINED IN THE SWELLING PRESSURE TEST WERE NOT SUCCESSFUL.

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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
  • Corporate Authors:

    Highway Research Board (HRB)

    Washington, DC   
  • Authors:
    • Mills, R H
  • Publication Date: 1966

Media Info

  • Media Type: Print
  • Features: Figures; Photos; References; Tables;
  • Pagination: pp 84-111
  • Monograph Title: Symposium on structure of Portland cement paste and concrete
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00212455
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Nov 18 1994 12:00AM