Dimensional change and elastic behavior of hardened portland cement paste, Ca-montmorillonite and 1.4 nm tobermorite: a comparative study
نویسنده
چکیده
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 1 and 2 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 environments, Beaudoin et al. (1). This may have an impact on the micro and nanostructural integrity of the binder in concrete and its durability. An improved understanding of the nature of C-S-H in hydrated cement products, the energetics of its interaction with water and the corresponding changes in engineering characteristics may lead to new technologies for enhanced service-life of concrete structures. Models of C-S-H nanostructure, generally derived from an eclectic body of physicochemical evidence, have been useful but not definitive in explaining durability phenomena, Taylor (2). The evolution of these models has provided an appreciation
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