Characterization of microstructural damage evolution of freeze-thawed shotcrete by an integrative micro-CT and nanoindentation statistical approach

It is crucial to investigate the evolution of microstructure to understand the deterioration mechanisms of shotcrete under cyclic freezing and thawing (F-T). In this study, nanoindentation and X-ray micro-CT techniques are integrated to characterize microstructural damage of shotcrete and its evolution due to F-T actions. An integrated statistical method of nanoindentation and micro-CT (NI-MCT) is developed with the Gaussian mixture deconvolution method to demonstrate the increase and correlation of the heterogeneous phase in cement paste and interfacial transition zones in the process of F-T cycles. The micromechanical property allows to segment the micro-CT images of cement paste into pores/cracks, porous phase, calcium silicate hydrate, and calcium hydroxide/unhydrated clinker. The integrated NI-MCT method can provide new knowledge on the evolution law of F-T-induced damage in cement paste and serve as an effective tool in characterizing and quantifying the damage and its evolution process for cement-based heterogeneous materials.

Automated summary

An integrated method combining nanoindentation and micro-CT was developed to investigate the microstructural damage and evolution of shotcrete under cyclic freezing and thawing. The study revealed an increase in heterogeneous phase in cement paste and correlation with interfacial transition zones during freezing and thawing cycles.