Three-dimensional imaging of cement microstructure evolution during hydration

Synchrotron radiation is used for X-ray computed tomography to characterise the hydration process of Portland cement. Quantitative determination of the three-dimensional absorption coefficient distribution due to the use of monochromatic radiation and the achieved high spatial resolution allows the study of the spatial microstructure of cement volume during hydration. The present study has demonstrated the potential of the method for real-time imaging of the evolution of cement structure after solidification. The method yields three-dimensional (3-D) images of the sample volume in a non-destructive manner. Thus, by reiterated imaging of the same sample region at different times, processes in the sample volume can be tracked. During cement hydration, effects such as the formation and further evolution of microcracks and pores – mainly related to autogeneous shrinkage – could be observed for the first time in the cement volume with up to 1 μm resolution. Image analysis of the acquired 3-D data sets allows the determination of the temporal evolution of microporosity and of the fraction of contiguous pore volume for different water : cement ratios of the initial cement paste.