دانلود رایگان مقاله اثر متقابل بین سودا کلسیم سیلیکات (C-S-H) و کلرید کلسیم، برمید و نیترات

Abstract

The interaction between C-S-H and anions, especially chloride, is already well documented. However, the conclusions vary from one author to another and a comparison of the obtained data is not always possible. Thus, this study aims to clarify this phenomenon and extend it to the case of bromide and nitrate. For this matter, a new analytical method has been developed in order to make the measurement directly in synthetic C-S-H suspensions, i.e. without any filtration, after calcium salt addition. Various parameters have been taken into account: the anion type and concentration, the Ca/Si of the C-S-H particles (ranging from 0.8 to 1.42) and the incorporation of aluminum inside the C-S-H structure. It has been found that there is no specific adsorption of chloride, bromide or nitrate by C-S-H. Calcium adsorption, which has been detected and measured, is limited, whatever the initial Ca/Si, and the presence of aluminum does not have any influence on it.

5. Conclusion

An automatic in situ analysis method of colloidal systems has been developed for this study to overcome a problem of reproducibility. This method is based on the use of specific electrodes directly immersed in C-S-H suspensions and has been applied to the study of ion adsorption by C-S-H particles. The main finding is that chlorides, bromides and nitrates do not adsorb on C-S-H particles although they tend to accumulate in the diffuse layer where they compete with OH−. The addition of calcium salt increases very slightly the calcium to silicon ratio of the initial C-S-H particles. The incorporation of aluminum the C-S-H structure has no influence on this calcium adsorption and therefore on the surface charge of the particles.