Investigation of the mechanical and microstructural properties of calcium aluminate cement based ternary systems which gained rapid strength

Calcium aluminate cement is a type of cement has superior properties compared to Portland cement, such as rapid strength gain, resistance to high temperatures, and harmful chemicals. Nevertheless, using calcium aluminate cement alone induces a series of chemical reactions called "conversion reaction" causing strength decreases and porosity increases. Using of these cement together with gypsum and mineral additives instead of using them alone is a highly preferred method in terms of both limiting strength drops and reducing costs. The addition of substitute materials that affect the hydration of these types of cement, whose hydration reactions are quite complex, have been making these mechanisms even more difficult to understand. The main purpose of this thesis is to understand the hydration mechanisms in binary and ternary systems produced with calcium aluminate cement with different oxide contents, silica fume and hemihydrate using various microstructural analysis methods. The hydration speed was accelerated by using LiSO4 in these systems and especially the hydration kinetics of the accelerated systems and the products formed as a result of hydration were investigated. In addition, the effects of nanomaterials on ternary systems were investigated by adding nano silica and nano sulfate additives to some mixtures. Thus, throughout the thesis, the strength reduces that may occur in calcium aluminate cement-based systems, the variation of the hydration products according to the amount and types of binder materials used, and the effects of these products on the mechanical properties have been extensively examined and discussed in a cause-effect relationship. According to the results obtained, it is clearly seen that the main hydration product, especially the hydration accelerated systems using LiSO4 is ettringite in these systems. On the other hand, straetlingite formation was increased in systems containing a high amount of silica fume, and this situation was limited strength decreases. In addition, the nano additives were increased the hydration rate of the systems but had no effect on the types of hydrated compounds. Specifically, in some mixtures that produce high amounts of ettringite at an early age, it has been observed that these ettringite fibers thin and elongate in the later stages of hydration and thus, paste structure has become porous and this was caused by expansions in the mortars and decreases in strength.