Consistent identification of the interfacial transition zone in simulated cement microstructures

A method to consistently identify the thickness of the interfacial transition zone (ITZ) between aggregates and bulk hardened cement paste (HCP) is proposed. Three different criteria to identify the boundaries of the ITZ are established, all based on the analysis of the trend of the effective water-to-cement ratio (w/c) close to an aggregate surface. The method is conceived so as to keep at minimum the operator intervention, thus permitting an objective evaluation of the ITZ thickness. The proposed procedure is applied to a series of ordinary Portland cement samples with different w/c ratios obtained using the code CEMHYD3D. The obtained results and the effects of the presence of the ITZ on the unhydrated and hydrated microstructures are analyzed and discussed.