Advances in characterizing and understanding the microstructure of cementitious materials

Abstract Progress in microstructural characterization methods is summarized. Special attention is given to advanced probes, such as X-ray imaging and spectroscopy, 1H NMR relaxometry, in-situ and high-pressure X-ray diffraction, and digital holographic microscopy. Microtomography has become a mature technique and nanotography has improved its spatial resolution significantly, particularly with the use of ptychography. The review also discusses the effect of plasticizers on the microstructure of concrete and presents a critical analysis of how organic admixtures affects the hydrates obtained from pure synthesis in saturated solutions and from more realistic hydrating systems. The addition of nanomaterials into cementitious systems modifies the microstructure of the matrix so a summary of recent research is presented. It is important to integrate the impressive progress in the characterization of the micro(nano)structure with efforts developing realistic models. Therefore, the present work gives a short but critical presentation of physical chemistry approaches that aim to link the chemical composition, texture, and microstructure of the cement hydrates.