Ion transport and microstructure of sandwich cementitious materials exposed to chloride environment

Abstract

Ion transport of sandwich cementitious materials (SCM) exposed to chloride environment was investigated by accelerated diffusion method and natural diffusion method. Pore structure and micromorphology of SCM were investigated by MIP and SEM-EDS. In comparison with the monolayer structural high performance concrete (HPC), conductive charge for 6 hours, chloride diffusion coefficient, and apparent chloride diffusion coefficient of SCM were decreased by 30%-40%, two orders of magnitude and 40%-50%, respectively. Pore structure of ultra low ion permeability cementitious materials (ULIPCM) prepared for the facesheet is superior to that of HPC prepared for the core. As for porosity, the most probable pore radius, the content of pores with radius ≥ 50 nm and the surface area of pores, the order is ULIPCM<HPC. The modifying degree of interfacial transition zone of the facesheet is much more than that of the core.

Keywords

sandwich / ion transport / pore structure / micromorphology

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