1.4 nm TOBERMORITE A COMPARATIVE STUDY.pdf

Dimensional change and elastic behavior of hardened Portland cement paste, Ca-montmorillonite and 1.4 nm tobermorite: a comparative study Beaudoin, J.J.; Mitchell, L.; Raki, L. NRCC-46433 A version of this document is published in / Une version de ce document se trouve dans: Advances in Cement and Concrete, Engineering Conferences International, Colorado, U.S.A., August 10-14, 2003, pp. 201-209 http://irc.nrc-cnrc.gc.ca/ircpubs DIMENSIONAL CHANGE AND ELASTIC BEHAVIOR OF HARDENED PORTLAND CEMENT PASTE, Ca-MONTMORILLONITE AND 1.4 nm TOBERMORITE: A COMPARATIVE STUDY J.J. Beaudoin, L. Mitchell and L. Raki Institute for Research in Construction National Research Council Ottawa, Ontario, Canada K1A 0R6 T: 1-613-993-6749; F: 1-613-954-5984; E: jim.beaudoin@nrc-cnrc.gc.ca ABSTRACT The role of water in hardened Portland cement paste (hpc) is germane to an understanding of the nature of nanostructure – property relationships. The irreversible dimensional changes of hpc that occur on wetting and drying are dissimilar to those observed for other silicate minerals of interest to cement science. This irreversibility is also observed for the modulus of elasticity parameter. Length change, mass change and modulus of elasticity isotherms (including 1st and 2nd drying-wetting cycles) were determined for specimens of hpc, montmorillonite and 1.4 nm tobermorite. All exhibit significant irreversible behavior. Similarities and differences in the nature and character of the three types of isotherms are discussed. Inferences are made with respect to the nanostructural nature of hpc and its dimensional response in aqueous media. It is apparent that hpc has unique characteristics that are responsible for stability. INTRODUCTION The volume stability and performance of cement-based materials are known to be affected by the response of the C-S-H in aggressive environ