Fig. 4: 4D nanoimaging study highlighting the etch-pit evolution.

a PXCT orthoslices at the studied hydration ages showing the evolution of the PC-52.5-w/c∼0.40 paste which includes: i) dissolution of cement particles, ii) portlandite growth, iii) C-S-H gel densification at 2 and 4 days, and iv) chemical shrinkage. Examples of these features are labelled with red arrows. b 3D rendering of a volume including a fraction of large alite particle highlighted in a, to show the evolution of five selected etch-pits, which are labelled. These images also show the full reaction of small alite particles, featured with blue circles. These 3D rendered views do not show exactly the electron densities as they are affected by visualization features like the lighting source. c 3D representation of the segmented particle, shown in the previous panels, to highlight the evolution of the etch-pits. It is noted that three branches within etch-pit #1 at 47 h coalesce at 93 h of hydration which may mean a reduction in surface with hydration time.