6533b7ddfe1ef96bd127448b

RESEARCH PRODUCT

In situ analysis of suspensions of calcium silicate hydrate : application to the study of ionics interactions at the surface of the particules

subject

description

This project aims to study the interactions between calcium silicate hydrate (C-S-H) and different anions (chlorides, bromides, nitrates and sulfates) in order to build a thermodynamic model and then be predictable. The simplified system CaO-SiO2-H2O is studied by synthesizing C-S-H suspensions and mixing them with different kind of salts (calcium salt or alkali salt). The influence of the temperature and the presence of aluminum in the structure of the C-S-H is also examined.A classical way to investigate this kind of system is to separate the liquid phase from the solid phase in order to analyze them separately. Nevertheless, this step has a large influence on the system, and the experimental results suffer from a really bad reproducibility.Another analysis method has then been developed in order to avoid the separation of the different phases. The results show that there is no adsorption of chlorides, bromides or nitrate on the surface of the C-S-H. They only have a role as a charge compensator in the diffuse layer around the particles in suspension.The calcium cation (in the case of calcium salt addition) can be adsorbed by C-S-H, but in a small quantity. The substitution of silicon by aluminum in C-S-H doesn’t have any influence on this phenomenon. A higher or lower temperature results in a weaker adsorption, even inexistent.Those experimental results have been reproduced by using a thermodynamic model developed in a previous study. Thus, the validity of the experimental part but also the one of the model are confirmed.