Calcium-Silicate-Hydrate (C-S-H) – xCaO.ySiO2.zH2O – is essentially the glue of a cement matrix which consists roughly 50% of C-S-H. Although cement-based materials are complex multiphase materials, C-S-H is the dominant phase controlling its performance. Knowledge of the exact nature of C-S-H, its nano/microstructure and degradation mechanisms is essential to improve significantly the ability to predict and control the performance of cementitious materials, more particularly those used for the encapsulation of radioactive wastes and geological disposal.
This PhD project aims at performing a comprehensive experimental study to assess the nano level of C-S-H to fundamentally understand the changes in structure and chemical composition of C-S-H under chemical degradation by carbonation, leaching and recalcification. Various types of C-S-H (real and synthetic) with different Ca/Si ratios will be subjected to a number of degradation conditions to understand the C-S-H degradation mechanism. A variety of characterization techniques will be used to quantify the change in chemistry and structure of C-S-H, which is combined with modelling approach in order to explore the effect of different degradation mechanisms, this may lead to engineering of cementitious materials with highly durable C-S-H.