Improved evidence for the existence of an intermediate phase during hydration of tricalcium silicate

By Franz Bellmann, D. Damidot, Bernd Moeser, J. Skibsted. 2010

136 citations recorded by the source corpus.

Abstract Tricalcium silicate (Ca 3 SiO 5 ) with a very small particle size of approximately 50 nm has been prepared and hydrated for a very short time (5 min) by two different modes in a paste experiment, using a water/solid-ratio of 1.20, and by hydration as a suspension employing a water/solid-ratio of 4000. A phase containing uncondensed silicate monomers close to hydrogen atoms (either hydroxyl groups or water molecules) was formed in both experiments. This phase is distinct from anhydrous tricalcium silicate and from the calcium–silicate–hydrate (C–S–H) phase, commonly identified as the hydration product of tricalcium silicate. In the paste experiment, approximately 79% of silicon atoms were present in the hydrated phase containing silicate monomers as determined from 29 Si{ 1 H} CP/MAS NMR. This result is used to show that the hydrated silicate monomers are part of a separate phase and that they cannot be attributed to a hydroxylated surface of tricalcium silicate after contact with water. The phase containing hydrated silicate monomers is metastable with respect to the C–S–H phase since it transforms into the latter in a half saturated calcium hydroxide solution. These data is used to emphasize that the hydration of tricalcium silicate proceeds in two consecutive steps. In the first reaction, an intermediate phase containing hydrated silicate monomers is formed which is subsequently transformed into C–S–H as the final hydration product in the second step. The introduction of an intermediate phase in calculations of the early hydration of tricalcium silicate can explain the presence of the induction period. It is shown that heterogeneous nucleation on appropriate crystal surfaces is able to reduce the length of the induction period and thus to accelerate the reaction of tricalcium silicate with water.

Subfields: Biomaterials, Civil and Structural Engineering, Earth-Surface Processes

View Paper: https://www.semanticscholar.org/paper/d107f9f5f29a6eb45632e98dd46c3fb475c8eadd

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Citations in the corpus

Ion-specific effects influencing the dissolution of tricalcium silicate (2014, background): “This point could be a factor influencing the duration of the so-called dormant period; a phenomenon not fully explained and still debated [8,62,63].”
Thermodynamics and cement science (2011, background): “Of course, it is long known that the dissolution is apparently incongruent and restricted due to both the formation of an intermediate phase slightly differing in composition from tricalcium silicate on its surface and precipitation of C–S–H [81].”