Effect of Condensed Silica Fume on the Mechanism of Chloride Diffusion Into Hardened Cement Paste

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Title: Effect of Condensed Silica Fume on the Mechanism of Chloride Diffusion Into Hardened Cement Paste

Author(s): Olav Gautefall and Jan Havdahl

Publication: Special Publication

Volume: 114

Issue:

Appears on pages(s): 849-860

Keywords: blended cements; cement pastes; chlorides; diffusion; portland cements; silica fume; water-cement ratio; Materials Research

Date: 5/1/1989

Abstract:
Reports on study of the chloride distribution profile in hardened cement paste cylinders of 5 cm diameter. The specimens were made from ordinary portland cement and blended cement with 10 percent fly ash. The condensed silica fume was used as cement replacement, with replacement levels of 5, 10, and 15 percent by weight of cement. Other experimental variables were water-to-(cement + silica fume) ratio of 0.5, 0.7, and 0.9. The specimens were immersed in stagnant seawater at 20 C. After 6 months of exposure, the specimens were cut, ground, dried, and the chloride ion content determined by a potentiometric titration procedure. By applying Fick's second law, the effective diffusion coefficient and the effective supply concentration of chloride were calculated by using an approximation method. Results show the effective diffusion coefficient is reduced highly when condensed silica fume is used as cement replacement.