|
Title |
Experiment on Chloride Adsorption by Calcium Aluminate Phases in Cement
|
|
DOI |
https://doi.org/10.4334/JKCI.2017.29.4.389 |
|
Keywords |
friedel’s salt ; chloride adsorption ; C3A phase ; C4AF phase ; AFm phase |
|
Abstract |
Friedel’s salt is an important product of chemical adsorption between cement hydrate and chloride ions because it contains chlorine in its structure. When cement reacts with water in the presence of chloride ions, the C3A phase, and C4AF phase react with chloride to produce Friedel’s salt. If chloride ions penetrate into concrete from external environments, many calcium aluminate hydrates, including AFm, can bind chloride ions. It is very important, therefore, to investigate the chloride binding isotherm of C3A phase, C4AF phase, and AFm phase to gain a better understanding of chloride binding in cementitious materials. Meanwhile, the adsorption isotherm can provide us with the fundamental information for the understanding of adsorption process. The experimental results of the isotherm can supply not only the quantitative knowledge of the cement-Friedel’s salt system, but also the mechanism of adsorption and the properties of their interactions. The purpose of this study is to explore the time dependant behaviors of chloride ions adsorption with C3A, C4AF and AFm phases. The chloride adsorption isotherm was depicted with Langmuir isotherm and the adsorption capacity was low in terms of the stoichiometric point of view. However, the chloride adsorption of AFm phase was depicted with Freundlich isotherm and the value was very low. Since the amount of the adsorption was governed by temperature, the affecting parameters of isotherm were expressed as a function of temperature.
|