Atomistic Simulation studies of the Cement Paste Components

Aluminium Incorporation to the C-S-H gel Silicate Chains
Chapter 4:
Aluminium Incorporation to C-S-H gel
Silicate Chains
4.1. Introduction and Computational method
4.2. Stability of the silicate chains: the 3n – 1 rule
4.3. Silicate chain growth and structure
4.4. Position of the aluminium within the silicate chains
4.5. Conclusions
4.1. Introduction and computational method
Among all the guest ions that might enter into the C-S-H structure, aluminium is the
most common one. By looking at table 1.2.1 in chapter 1, it can be seen that Al 2 O 3 is
the third oxide in amount in the ordinary Portland cement clinker. Although aluminium
takes part in several AFm and AFt crystalline phases, Copeland et al. shown that these
hydration products do not account for all the aluminium present in the cement paste
[181], and therefore aluminium should take part in the C-S-H gel. The aluminium
incorporation is expected to modify the C-S-H gel properties and many processes such
as ion exchange behaviour, the solubility, and the reactions during delayed ettringite
formation [182-184]. Furthermore, slag- and fly ash-based cements, which employ
residual wastes as raw materials, have a high aluminium content [185]. Hence, the
mechanism and effect of aluminium incorporation to the C-S-H gel is of great
technological interest, and must be investigated.
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