Title:
Chloride Adsorption of Cement Hydrates Combined with Chemical Evolution of Pore Solution
Author(s):
In-Seok Yoon and Tatsuhiko Saeki
Publication:
Materials Journal
Volume:
121
Issue:
5
Appears on pages(s):
51-62
Keywords:
alumina, ferric oxide, monosubstituted (AFm) phase; Ca/Si ratio; calcium-silicate-hydrate (C-S-H) phase; chloride adsorption; Friedel’s salt
DOI:
10.14359/51742037
Date:
9/1/2024
Abstract:
In this study, a chloride adsorption test was performed to depict
the chemical evolution of pore solution for cement hydration. It
was found that the amount of chloride adsorbed by the AFm phase
and the calcium-silicate-hydrate (C-S-H) phase decreased with
the increasing pH of the pore solution. The stability of Friedel’s
salt tended to decrease with the increasing pH of the pore solution.
Notably, in the C-S-H phase, the decrease in the amount of chloride
adsorption resulting from an increase in the pH level was larger
when the Ca/Si ratio was higher. Based on these works, multiple
regression analysis was performed to examine the correlation
between the chloride adsorption density of cement hydrates and
the experimental variables involved, including the pH of the pore
solution and the amount of chloride-ion penetration.
The pH of the pore solution was predicted based on cement hydration and pore-chemistry theories, and these results were combined with the experimental results, considering the changing chemical characteristics of the pore solution during each temporal stage of cement hydration. The amount of chloride-ion adsorption in fly ash (FA) and granulated blast-furnace slag (GBFS) was larger than in ordinary portland cement (OPC) due to the decreased pH of the pore solution resulting from the consumption of calcium hydroxide.