Gradient-based phase segmentation method for characterization of hydrating cement paste microstructures obtained from X-ray micro-CT

X-ray micro-computed tomography (micro-CT) has been widely used in the non-destructive investigation of 3D microstructures of cementitious materials. Microstructures from micro-CT are reconstructed from the attenuated transmitted X-ray intensity through a sample or linear attenuation coefficient (LAC). Although uncertainties can be introduced during processes, such as data collection and microstructure reconstruction, the LAC values are determined based on the X-ray energy level and material composition so that they can be considered as almost absolute measures. In this study, the microstructural evolution of cement paste during hydration was investigated using microstructures with a 4.5 mu m voxel size obtained from X-ray micro-CT. A new phase segmentation method based on the mean LAC values for the pore and unhydrated phases inside the binder was developed. The pore phase features were characterized by porosity, equivalent pore diameter, and two-point probability functions. The findings indicate that the proposed segmentation method is well adapted for micro-CT imaging to identify the characteristics of pores, hydrates, and clinkers.