Synchrotron X-ray micro-tomography investigation of the early hydration of blended cements: A case study on CaCl2-accelerated slag-based blended cements

In situ X-ray Micro-Tomography (XMT) analyses with a pixel size of 0.325 mu m were conducted on slag-based blended cements containing 75% of Ground-Granulated Blast-Furnace Slags (GGBS) and 25% of Ordinary Portland Cement (OPC), with or without CaCl2 acceleration. Results show the identification of the main cementitious phases and the need to perform data repeatability tests in order to allow their quantification. Investigation of the early hydration during the first 31 h of hydration by image subtraction showed (i) the dissolution of OPC/GGBS, (ii) the precipitation of hydrates including C-S-H, (iii) the accelerating effect of CaCl2, and (iv) phase-identification based on their specific grey level.