Date and place of thesis defense:
16.06.2008, Faculty of Metallurgy and Materials Science
mr. sc. Farzet Bikić
prof. dr. Mirsada Rizvanović
Influence of chemical bonding of Chlorides for aluminates in cement hidratation process onto corrosion intensity in concrete steel bars
Chlorides added in concrete in the preparation phase as accelerators of cement minerals bonding processes as well as chlorides which penetrate from the envornment into the concrete react with both aluminates and hydration aluminate products. These reactions result in two products. At the lower concentration of chlorides C3A•CaCl2•HX is formed, whereas at the higher concentrations it is C3A•3CaCl2•HY.
In everyday conditions, this was also confirmed by conducted research, monochloride-aluminate is formed a compound with one molecule of CaCl2, well known as Friedel's salt.
Results of this research confirm the above mentioned statement that addition of chloride during the preparation of concrete as well as penetration of chlorides from the environment result in forming monochloride-aluminate.
It was found that reactions between chlorides and aluminates are temperature dependant and that product quantity of these reactions increases with the temperature growth.
Free chlorides in concrete may cause the corrosion of steel bars. It was proven that growth of free chloride concentration in concrete leads to the increase of steel bars corrosion intensity. Bound chlorides do not affect the corrosion of concrete steel bar.
Process of chloride bonding is registered via XRD and DTA analyses as well as by measuring of the steel bar corrosion rate via anode-polarization curves.
Potentiodynamic research has shown that the increase in thermostating temperature of working electrodes (which were treated by chlorides in the preparation phase) leads to reduction in steel bars corrosion.
This research confirms the hypothesis that bonding of chlorides to aluminates results in decrease of corrosion intensity in concrete steel bars.