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  • 1990-1994  (3)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    In situ solid-state NMR studies of Ca3SiO5: hydration at room temperature and at elevated temperatures using 29Si enrichment (1994)
    Springer
    Journal of materials science 29 (1994), S. 3926-3940 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract 29Si isotopic enrichment was used for acquisition of multiple 29Si magic-angle spinning (MAS) and cross-polarization magic-angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectra, in situ in an NMR probe, from a single sample of hydrating Ca3SiO5 (C3S). Data with excellent signal-to-noise ratios were obtained at 20, 50 and 75 °C, with minimal use of spectrometer time, and without the need for the quenching of multiple samples. Spectral line widths and polymer-chain lengths derived from the spectra had no detectable differences from experiments in which the quenching was carried out with propan-2-ol. Furthermore, the effects of the MAS technique on the hydration reaction appeared to be minimal. At 20 °C, the bulk hydrate initially produced was dimeric; at later stages of the reaction, polymerization occurred. Arrhenius energies of 35 and 100 kJ mol−1, respectively, were calculated for these two reactions. The cross-polarization (CP) spectra acquired throughout the hydration showed that at 20 °C, 2% of the hydrated monomeric Q o (H) species persisted from after the induction period through to the late stages of the hydration reaction; this indicates that this species is unlikely to result from surface hydroxylation of C3S; an upfield shift of this species occurred with increasing hydration, indicating a possible change of environment for the silicate species. The amount of Q o (H) produced was found to increase at higher temperatures. Potential mechanisms for polymerization were assessed and a model in which dimeric-silicate units are linked together by insertion of monomers (dimer → pentamer → octomer) was found to give the best fit to the observed data; these results support a dreierketten model for the structure of the hydrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00355951
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Microstructure and microanalysis of hardened cement pastes involving ground granulated blast-furnace slag (1992)
    Springer
    Journal of materials science 27 (1992), S. 6204-6212 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The microstructure and composition of hardened cement pastes of a wide range of blends of ground granulated blast-furnace slag with ordinary Portland cement have been studied, using techniques of transmission electron microscopy with microanalysis combined with electron microprobe analysis. Throughout the range, a calcium silicate hydrate gel (C-S-H) is the dominant cementing phase, present in the “inner product” within the space originally occupied by either slag grains or alite or belite grains originating from the Portland cement, or in the “outer product” in the originally water-filled spaces. The morphology and composition of the outer product C-S-H and the composition of inner product C-S-H change with blend composition. Inner product of slag grains contains C-S-H of the same composition as the outer product C-S-H, intimately mixed with a Mg, Al-rich hydroxide phase whose fineness shows considerable variation. Inner product C-S-H of alite or belite does not differ significantly in Ca∶Si ratio from that of slag. The reduction of Ca∶Si ratio of all forms of C-S-H with increasing slag loading may have implications for the pH-buffering capacity of blends of large slag loading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133772
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Microstructure and microanalysis of hardened ordinary Portland cement pastes (1993)
    Springer
    Journal of materials science 28 (1993), S. 265-277 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Hardened ordinary Portland cement pastes of various ages have been examined by analytical transmission electron microscopy (TEM) and electron microprobe analysis (EMPA). The stability of the various hydrate phases in the electron microscope is discussed. Although all are subject to damage in varying degrees, even the least stable phase, AFt, can be recognized in relict form in the TEM. The basic framework of the microstructure and the differentiation into inner and outer hydration product are well-established at 24 h hydration. Although the dominant inner product formed within the boundaries of the original anhydrous grains is C-S-H gel, particles of AFt, AFm, Ca(OH)2, a magnesium-rich phase and an iron-rich phase are occasionally observed within the inner product. The Ca∶Si ratio of the C-S-H gel determined by TEM shows significant variation from one region to another in a given paste. There is no relationship between the average Ca∶Si ratio of the C-S-H and the maturity of the paste, although young pastes appear to show a bimodal distribution. Microanalysis by EMPA gives Ca∶Si ratios in substantial agreement with those found by TEM but it is essentially impossible to obtain by EMPA analyses of outer product C-S-H without admixture of other phases, particularly sulphoaluminate phases. Despite the presence of small amounts of embedded phases as revealed by TEM, single-phase inner product C-S-H can be analysed by EMPA. The compositions of AFt and AFm phases have been obtained by TEM and the results do not require the substitution of silicon in the formulae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349061
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    Paper (German National Licenses)
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