Sorption of Chloride-ion, Sulfate-ion and Phosphate-ion in Calcium Silicate Hydrates

Akinori NAKAMURA*, Etsuo SAKAI, Kenichi NISHIZAWA, Yoko OHBA and Masaki DAIMON

Department of Inorganic Materials, Tokyo Institute of Technology; 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552 Japan
Cement/Concrete & Building Materials Research Laboratory, Tokuyama Corp.; 1-1, Mikage-cho, Tokuyama-shi 745-8648 Japan

This study discusses the capacity of sorption of various ions in calcium silicate hydrates. Chloride-ion, sulfate-ion and phosphate-ion were sorbed in synthesized calcium silicate hydrates (C-S-H). The amount of sorbed chloride-ion, sulfate-ion and phosphate-ion in C-S-H were 172 mg/g, 54 mg/g and 667 mg/g, respectively. In the case of sorption of phosphate-ion, phosphate-ion and C-S-H reacted to produce hydroxyapatite. In the leaching test, 15% of chloride-ion, 18% of sulfate-ion and 34% of phosphate-ion were dissolved from C-S-H sorbing respective anions. On the other hand, 65% of fixed chloride-ion in Friedel's salt was dissolved in the leaching test. Therefore, the fixing ability of chloride-ion in C-S-H is higher than that in Friedel's salt.

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