Movement of Ions Through Mortar Mixed With Mineral Admixtures


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Title: Movement of Ions Through Mortar Mixed With Mineral Admixtures

Author(s): N. Otsuki, S. Nagataki, and M. Hisada

Publication: Special Publication

Volume: 153


Appears on pages(s): 297-314

Keywords: blast furnace slag; chlorides; fly ash; mineral admixtures; mortars (material); porosity; potassium; silica fume; sodium; Materials Research

Date: 6/1/1995

It is necessary for concrete engineers to get more information on the ion movement through and in concrete for the development of new technologies, such as cathodic protection, desalination, and re-alkalization for reinforced concrete members. In concrete members with these treatments, various ions should be moved through and in concrete members. The movement of ions could influence concrete properties and steel reinforcing bars. Ground granulated blast furnace slag, fly ash, and silica fume have been recognized as high quality mineral admixtures for concrete. Since structures built with these materials might eventually be subjected to electro-migration processes, a set of experiments to assess the effects of these pozzolans were devised. In this study, considering the conditions mentioned above, the movement of several kinds of ions through hardened mortar with mineral admixtures was investigated. As ions, Na +, K +, and Cl - were selected because the ions were closely related to alkali-aggregate reaction or chloride attack. As mineral admixtures, ground granulated blast furnace slag, fly ash, and silica fume were used. Also, the influences of water-to-binder ratio on the movement of ions were investigated. Electrochemical cells were used for the experimental work; the current was applied to a cell in the range between 0.1 A/m 2 and 10.0 A/m 2. Analyzing the data from the experimental work, the following conclusions were obtained. 1. The electromigration of ions through mortar are reduced with the addition of admixtures. 2. The electromigration of ions increases with the water-to-binder ratio. 3. The electromigration of ions is closely related to the pore size distribution of mortar and paste.