Characterization of ITZ in ternary blended cementitious composites: Experiment and simulation

In this paper, some results are presented referring to experiment and simulation on the characterization of the ITZ microstructure in ternary blended cement based composites. The backscattered electron (BSE) imaging technique is used to acquire images in experiment. Image analysis is applied based on two new algorithms: concentric expansion for strip delineation and overflow criterion for phase segmentation. Besides, a continuum integrated model HYMOSTRUC has been extended to simulate the coupled aggregate-ITZ-bulk paste microstructure. In particular, local water binder ratio and water transport have been incorporated to account for variable hydration conditions of cementitious particles in ITZ and bulk paste. Results indicate that a good agreement has been reached between experiment and simulation. The proposed image processing procedure is well implemented in the ITZ analysis of ternary blended composites, while local water binder ratio and water transport are two critical factors for the simulation of ITZ. For the designed ternary blended mortar, ITZ has been well differentiated from bulk paste quantitatively, i.e., higher porosity and lower anhydrous fraction, whilst the capillary pore connectivity does not seem to be different between ITZ and bulk paste in the current simulation.

► The BSE image analysis with regard to ITZ is well implemented by two new algorithms.
► Local water binder ratio and water transport are two critical factors for the numerical simulation of ITZ.
► A typical higher porosity and lower anhydrous fraction is found in the vicinity of aggregate.