Assessment of structural feature and ionic diffusivity of ITZ in blended cementitious composites

In this paper, we present a study about the assessment of structural feature and ionic diffusivity of interfacial transition zone (ITZ) in blended cementitious composites, which are made of Portland cement, blast furnace slag and limestone filler. In particular, three mortar series are examined with respect to varying replacement levels of supplementary cementitious materials (SCMs), curing age and water-to-binder (w/b) ratio. Based on the techniques of experimental measurement and numerical simulation, i.e., the backscattered electron (BSE) image analysis and the HYMOSTRUC model, the structural features of ITZ in designed mortars are elaborated in a quantitative manner. Thereafter, a lattice Boltzmann method based computer modeling of ionic diffusion in the ITZ is performed to predict the ionic diffusivity. Results indicate that the ITZ differs much from bulk paste, which is of significant importance in blended cementitious composites. The structural feature and the ionic diffusivity of ITZ are prominently affected by various casting factors, such as replacement levels of SCMs, curing age and w/b ratio.