The Impact of Tortuosity on Chloride Ion Diffusion in Slag-Blended Cementitious Materials

The purpose of this study is to determine the tortuosity of cementitious materials containing blast furnace slag (BFS). Furthermore, the influence of tortuosity on multi-species transport into these materials is studied. The porosity and diffusivity of calcium silicate hydrate (C-S-H) were predicted...

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Bibliographic Details
Published inJournal of Advanced Concrete Technology Vol. 15; no. 8; pp. 426 - 439
Main Authors Hatanaka, Akira, Elakneswaran, Yogarajah, Kurumisawa, Kiyofumi, Nawa, Toyoharu
Format Journal Article
LanguageEnglish
Published Tokyo Japan Concrete Institute 31.08.2017
Japan Science and Technology Agency
Subjects
Blast furnace slags
Calcium silicate hydrate
Calcium silicates
Cement
Chloride
Computer simulation
Corrosion
Electrical properties
Ion diffusion
Mathematical models
Mineralogy
Pore size distribution
Porosity
Portland cements
Sodium chloride
Spatial distribution
Species diffusion
Three dimensional models
Tortuosity
Transport
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Summary:The purpose of this study is to determine the tortuosity of cementitious materials containing blast furnace slag (BFS). Furthermore, the influence of tortuosity on multi-species transport into these materials is studied. The porosity and diffusivity of calcium silicate hydrate (C-S-H) were predicted using a three-dimensional spatial distribution model, which were then fitted to Archie’s law to determine tortuosity. The tortuosity increased with the slag replacement ratio, suggesting that the diffusion path for ions becomes complicated and lengthy due to slag addition. Thermoporometry was used to determine the pore size distribution of hydrated slag-blended cement. A partial replacement of ordinary Portland cement (OPC) with BFS modified the mineralogy (especially in the types of C-S-H), resulting in changes to the pore structure. The determined tortuosity and porosity were used in a reactive transport model to predict multi-species transport. Experimentally measured and simulated chloride profiles were in good agreement for hydrated OPC and slag-blended cements exposed to sodium chloride solutions. The causes for the low penetration rate of chloride in slag-blended cementitious materials are discussed considering their pore structure and surface electrical properties. The role of tortuosity on Cl-/OH- for the evaluation of chloride induced corrosion was also discussed.
ISSN:1346-8014
1347-3913
DOI:10.3151/jact.15.426