Pore structure development during hydration of tricalcium silicate by X-ray nano-imaging in three dimensions

Tricalcium silicate (C3S) is the most important component among the four main clinker phases of Portland cement. Pure C3S is widely used as a simplified model system of cement in various researches. However, the spatial structure development of cement, even pure C3S during hydration at the nano-scale has been rarely directly reported. In this work, X-ray nano-computed tomography (X-ray Nano-CT), a non-destructive X-ray analytical method, was used to study the hydration of a pure C3S sample with a water/C3S mass ratio of 0.5. The three-dimensional (3D) structure of the hydrating C3S specimen was investigated to see the internal pore structure evolution within the hardened C3S paste. Investigation of the 3D structural development of the C3S specimen at different hydration times was performed to monitor the changes of pore shapes and sizes/volumes. It is found that volumes of the sealed pores generally grow larger, and the open pores become smaller while the volume and the external morphology of the whole hardened C3S paste remains almost the same during hydration