Analysis of disorder in tricalcium silicate by 29Si NMR spectroscopy and additional methods

The disorder in the crystal lattice of four samples of tricalcium silicate was analyzed in a multi-method investigation. Chemical disorder introduced by the presence of dopant elements was kept constant. Physical disorder was modified by different annealing–cooling procedures and also by grinding. The triclinic polymorph of tricalcium silicate was present in quenched samples whereas after slow cooling a combination of monoclinic and triclinic polymorphs was detected by 29Si NMR spectroscopy. Annealing at 1500 °C for 6 h led to a significant reduction of specific surface area due to crystal growth. The reactivity of the samples tested by calorimetry indicated that the maximum heat release rate and the degree of hydration were affected by physical disorder in the samples. There was no correlation with other types of defects analyzed in this study or with the modification of the Gibbs free energy of the crystal lattice by the presence of defects.