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Zeng J.-J.,Key Laboratory of Harbor and Marine Structure Durability Technology of Ministry of Communications | Zeng J.-J.,China Communications Construction Company Ltd. | Wang S.-N.,Key Laboratory of Harbor and Marine Structure Durability Technology of Ministry of Communications | Wang S.-N.,China Communications Construction Company Ltd. | And 4 more authors.
Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of Technology

Concretes were prepared with cement solely substituted by metakaolin (MK) and double substituted by MK and fly ash (FA) or slag (GGBS). Concrete chloride diffusion coefficient was tested both by NT BUILD 443 and NT BUILD 492, while the pore structure of concrete was tested by MIP. In addition, cement pastes were prepared with the same cementitious materials with the concretes, and NaCl was incorporated during the preparation process. The total and free chloride contents of pastes were tested by automatic potentiometric titrator, and the chloride binding rate was also calculated. The phase compositions of the pastes were analyzed by XRD. The experimental results revealed that chloride diffusion coefficient of concrete decreased significantly by MK, especially when FA or GGBS were blended. The chloride diffusion coefficient at the later stage obviously decreased when MK and FA were double blended. The chloride binding rate of the pastes increased with the incorporation of MK. The higher the replacement level, the higher the binding rate. The binding effect improved if FA or GGBS was blended, especially for FA. MK can refine the concrete pore structure, reduce capillary pore volume, promote the appearance of Friedel salt, decrease the chloride transport way and enhance chloride binding capacity with the incorporation of MK for marine concrete, which can improve the chloride penetration resistance. ©, 2015, Wuhan University of Technology. All right reserved. Source

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