No abstract

No abstract

No abstract

This research is part of a European project (namely, CÓDICE project), main objective of which is modelling, at a multi-scale, the evolution of the mechanical performance of non-degraded and degraded cementitious matrices. For that, a series of experiments were planned with pure synthetic tri-calcium silicate (C3S) and bi-calcium silicate (C2S) (main components of the Portland cement clinker) to obtain different calcium-silicate-hydrate (C-S-H) gel structures during their hydration. The characterization of those C-S-H gels and matrices will provide experimental parameters for the validation of the multiscale modelling scheme proposed. In this article, a quantitative method, based on thermal analyses, has been used for the determination of the chemical composition of the C-S-H gel together with the degree of hydration and quantitative evolution of all the components of the pastes. Besides, the microstructure and type of silicate tetrahedron and mean chain length (MCL) were studied by scanning electron microscopy (SEM) and Si magic-angle-spinning (MAS) NMR, respectively. The main results showed that the chemical compositions for the C-S-H gels have a CaO/ SÍO2 M ratio almost constant of 1.7 for both C3S and C2S compounds. Small differences were found in the gel water content: the H 2 0/Si0 2 M ratio ranged from 2.9 ± 0.2 to 2.6 ± 0.2 for the C 3 S (decrease) and from 2.4 ± 0.2 to 3.2 ± 0.2 for the C 2 S (increase). The MCL values of the C-S-H gels, determined from 29 Si MAS NMR, were 3.5 and 4 silicate tetrahedron, for the hydrated C3S and C2S, respectively, remaining almost constant at all hydration periods. Keywords C-S-H gel • Chemical composition • Thermal analysis • C3S • C2S