THE NEW MODEL OF HARDENED PORTLAND CEMENT PASTE

FELDMAN AND SEREDA REJECT THE POWERS MODEL OF THE STRUCTURE OF HARDENED PORTLAND CEMENT PASTE ON THE GROUND THAT THE BET SURFACE AREA AND THE POROSITY OF D-DRIED PASTES AS MEASURED BY WATER VAPOR ADSORPTION IS WRONG BECAUSE FOUR-FIFTHS OF THE UPTAKE OF WATER IS INTERLAYER WATER AND NOT ADSORBED WATER. THEY PROPOSE THAT NITROGEN ADSORPTION MEASURES THE SURFACE APPROXIMATELY CORRECTLY AND, ON THE BASIS OF THESE IDEAS, PRESENT A NEW MODEL OF PASTE STRUC- TURE. THE PRESENT PAPER SHOWS THAT WATER VAPOR ADSORPTION MEASURES THE SURFACES AND POROSITIES OF DRIED PASTES CORRECTLY, WHEREAS NITROGEN MEASURES ONLY PART OF THE SURFACE AND POROSITY. D-DRIED PASTES HAVE NO INTERLAYER WATER NOR ADSORBED WATER. PORE STRUCTURE ANALYSIS SHOWS THAT NITROGEN CANNOT PENETRATE INTO MANY LARGE PORES. COMPLETELY HYDRATED D-DRIED PASTES OF THE SAME CEMENT HAVE THE SAME SURFACE AREA WHEN MEASURED BY WATER ADSORPTION REGARDLESS OF W/C, WHEREAS NITROGEN AREAS VARY BY A FACTOR OF ALMOST 3. THE DATA OF FELDMAN AND SEREDA SHOW THAT THEIR QUICK-DRYING PROCEDURE IS APPROXIMATELY EQUIVALENT TO P-DRYING. P-DRIED PASTES CONTAIN BOTH INTERLAYER WATER AND ADSORBED WATER. THE ENERGIES OF BINDING OF THESE 2 TYPES OF WATER STRONGLY OVERLAP; CONSEQUENTLY, THEY CANNOT BE SEPARATED BY TESTS OF REVERSIBILITY. FURTHERMORE, BECAUSE OF THE DIFFERNET DRYING PROCEDURE, NO CONCLUSION CAN BE DRAWN FROM THE EXPERIEMENTS OF FELDMAN AND SEREDA FOR D-DRIED PASTES. THE AUTHORS OF THE NEW MODEL CONTEND THAT NO EQUILIBRIUM IS REACHED IN THE SURFACE AREA MEASUREMENTS BY WATER ADSORPTION ON D-DRIED PASTES. IT IS SHOWN IN THE PRESENT PAPER THAT EQUILIBRIUM WAS REACHED IN THSES MEASUREMENTS BUT WAS NOT REACHED IN MOST OF THE EXPERIMENTS OF FELDMAN AND SEREDA. THEIR DESORPTION ISOTHERMS, AS WELL AS THE LOOPS, BY WHICH THEY ATTEMPT TO TEST REVERSIBILITY, REPRESENT NONEQUILIBRIUM CONDITIONS. THE MAIN CONCLUSION OF THE PAPER IS THAT THE AUTHORS KNOW OF NO PROPERLY INTERPRETED EVIDENCE TO DATE THAT CONTRADICTS THE POWERS MODEL. /AUTHOR/

  • Digital Copy:
  • Supplemental Notes:
    • Paper sponsored by Committee on Basic Research Pertaining to Portland Cement and Concrete and presented at the 49th Annual Meeting.
  • Authors:
    • Brunauer, Stephen
    • Odler, Ivan
    • Yudenfreund, Marvin
  • Discussers:
    • FELDMAN, R F
    • Sereda, P J
    • Seligmann, Paul
  • Publication Date: 1970

Media Info

  • Media Type: Print
  • Features: References; Tables;
  • Pagination: pp 89-107
  • Monograph Title: Concrete durability, cement paste, aggregates and sealing compounds
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00213854
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Feb 8 1971 12:00AM