Understanding Of Hydration Mechanism Research Articles

Alite hydration at the single grain level

Understanding cement hydration processes is crucial for achieving the desired properties in concrete. However, the nanoscale mechanism whereby calcium silicate hydrate (C–S–H) transforms, particularly regarding morphology, structure, and composition evolution, remains unclear. Here, we employed multimodal transmission electron microscopy (TEM) to investigate the hydration kinetics of alite at the single grain level, extracting comprehensive chemical and structural information. Our findings reveal that rapid nucleation of C–S–H occurs at the boundaries within minutes, followed by subsequent C–S–H growth. The development of C–S–H fibrils can be categorized into two distinct stages: needle elongation and texture densification. Through quantitative analysis, we estimated the growth rate of C–S–H needles to be 7 nm/min, while observing a decrease in the intrinsic porosity of C–S–H from 7.9% to 3.1% concurrent with the thickening of C–S–H lamella. Electron diffraction analysis further demonstrates the homogenization of C–S–H throughout hydration, involving structural compaction and silicate polymerization. Our work provides valuable insights into the origins of C–S–H nucleation and growth, thereby enhancing our understanding of hydration mechanisms at a fundamental level.

Investigation of C3 S hydration mechanism by transmission electron microscope (TEM) with integrated Super-XTM EDS system.

Tricalciumsilicate (C3 S, Alite) is the major component of the Portland cement clinker. Hydration of Alite is decisive in influencing the properties of the resulting material. This is due to its high content in cement. The mechanism of the hydration of C3 S is very complicated and not yet fully understood. There are different models describing the hydration of C3 S in various ways. In this work for a better understanding of hydration mechanism, the hydrated C3 S was investigated by using the transmission electron microscope (TEM) and for the first time, the samples for the investigations were prepared by using of focused ion beam from sintered pellets of C3 S. Also, an FEI Talos F200x with an integrated Super-X EDS system was used for the investigations. FEI Talos F200X combines outstanding high-resolution S/TEM and TEM imaging with energy dispersive X-ray spectroscopy signal detection, and 3D chemical characterization with compositional mapping. TEM is a very powerful tool for material science. A high energy beam of electrons passes through a very thin sample, and the interactions between the electrons and the atoms can be used to observe the structure of the material and other features in the structure. TEM can be used to study the growth of layers and their composition. TEM produces high-resolution, two-dimensional images and will be used for a wide range of educational, science and industry applications. Chemical analysis can also be performed. The purpose of these investigations was to get the information about the composition of the C-S-H phases and some details of the nanostructure of the C-S-H phases.

Hydration properties of durum wheat semolina: influence of particle size and temperature

The hydration of semolina particles is an essential step in couscous processing which leads to binding between particles for the formation of agglomerates. Despite this importance, the hydration properties of such food products are rarely studied and in particular, durum wheat semolina has never been investigated. Here we present a study of the hydration properties of durum wheat semolina by determination of water sorption isotherms, and other characterisation techniques to obtain a better understanding of hydration mechanisms. Equilibrium and dynamic sorption properties have been measured as a function of relative humidity by means of a controlled atmosphere microbalance. It is found that durum wheat semolina presents a type II isotherm [F. Rouquerol, J. Rouquerol, K. Sing, Adsorption by Powders and Porous Solids—Principles Methodology and Applications, Academic Press, 1999] indicative of multi-layer adsorption. The Guggenheim–Anderson–de Boer (GAB) model is used to describe the isotherm and obtain a better understanding of hydration mechanisms and liquid/solid interactions. The effects observed are related to physical properties of the semolina. In particular, the size of the semolina particles is found mainly to influence sorption kinetics: the finer the particles, the faster their sorption kinetics. Increasing temperature in the range 25–45 °C accelerates sorption kinetics. Furthermore, hydration causes no irreversible transformation of semolina components. Thus, absorption kinetics seem to be influenced by physical mechanisms, while the biochemical composition determines the amount of water sorbed.