C-S-H Pore Size Characterization Via a Combined Nuclear Magnetic Resonance (NMR)-Scanning Electron Microscopy (SEM) Surface Relaxivity Calibration

The nucleation of C-S-H via prenucleation clusters

The nucleation and growth of calcium-silicate-hydrate (C-S-H) is of fundamental importance for the strength development and durability of the concrete. However, the nucleation process of C-S-H is still not fully understood. The present work investigates how C-S-H nucleates by analyzing the aqueous phase of hydrating tricalcium silicate (C₃S) by applying inductively coupled plasma-optical emission spectroscopy as well as analytical ultracentrifugation. The results show that the C-S-H formation follows non-classical nucleation pathways associated with the formation of prenucleation clusters (PNCs) of two types. Those PNCs are detected with high accuracy and reproducibility and are two species of the 10 in total, from which the ions (with associated water molecules) are the majority of the species. The evaluation of the density and molar mass of the species shows that the PNCs are much larger than ions, but the nucleation of C-S-H starts with the formation of liquid precursor C-S-H (droplets) with low density and high water content. The growth of these C-S-H droplets is associated with a release of water molecules and a reduction in size. The study gives experimental data on the size, density, molecular mass, and shape and outlines possible aggregation processes of the detected species.

Reconstruction of calcium silicate hydrates using multiple 2D and 3D imaging techniques: Light microscopy, μ-CT, SEM, FIB-nT combined with EDX

This study demonstrates the application and combination of multiple imaging techniques [light microscopy, micro-X-ray computer tomography (μ-CT), scanning electron microscopy (SEM) and focussed ion beam - nano-tomography (FIB-nT)] to the analysis of the microstructure of hydrated alite across multiple scales. However, by comparing findings with mercury intrusion porosimetry (MIP), it becomes obvious that the imaged 3D volumes and 2D images do not sufficiently overlap at certain scales to allow a continuous quantification of the pore size distribution (PSD). This can be overcome by improving the resolution and increasing the measured volume. Furthermore, results show that the fibrous morphology of calcium-silicate-hydrates (C-S-H) phases is preserved during FIB-nT. This is a requirement for characterisation of nano-scale porosity. Finally, it was proven that the combination of FIB-nT with energy-dispersive X-ray spectroscopy (EDX) data facilitates the phase segmentation of a 11 × 11 × 7.7 μm³ volume of hydrated alite.

Study on the Adhesion Performance of Asphalt-Calcium Silicate Hydrate Gel Interface in Semi-Flexible Pavement Materials Based on Molecular Dynamics

The interface between an asphalt binder and a calcium silicate hydrate (C-S-H) gel is a weak point of semi-flexible pavement material. In this study, the adhesion performance of asphalt-C-S-H gel interface in semi-flexible pavements at a molecular scale has been investigated. Molecular dynamics (MD) simulations were applied to establish three asphalt binders: 70# asphalt binder (the penetration is 70 mm), PG76-22 modified asphalt binder (a kind of asphalt binder that can adapt to the highest temperature of 76 °C and the lowest temperature of -22 °C), and S-HV asphalt binder (super high viscosity). The effects of different temperatures and SBS modifier contents on interfacial adhesion were explored. The obtained results showed that temperature variations had little effect on the adhesion work of the asphalt-C-S-H gel interface. It was also found that by increasing the content of SBS modifier, the adhesion work of the asphalt-C-S-H gel interface was increased. The molecular weight of each component was found to be an important factor affecting its molecular diffusion rate. The addition of SBS modifier could regulate the adsorption of aromatics by C-S-H gel in the four components of asphalt binder and improve the adsorption of resins by C-S-H gel.

An Ontology-Based Approach to Enable Data-Driven Research in the Field of NDT in Civil Engineering

Although measurement data from the civil engineering sector are an important basis for scientific analyses in the field of non-destructive testing (NDT), there is still no uniform representation of these data. An analysis of data sets across different test objects or test types is therefore associated with a high manual effort. Ontologies and the semantic web are technologies already used in numerous intelligent systems such as material cyberinfrastructures or research databases. This contribution demonstrates the application of these technologies to the case of the 1H nuclear magnetic resonance relaxometry, which is commonly used to characterize water content and porosity distribution in solids. The methodology implemented for this purpose was developed specifically to be applied to materials science (MS) tests. The aim of this paper is to analyze such a methodology from the perspective of data interoperability using ontologies. Three benefits are expected from this approach to the study of the implementation of interoperability in the NDT domain: First, expanding knowledge of how the intrinsic characteristics of the NDT domain determine the application of semantic technologies. Second, to determine which aspects of such an implementation can be improved and in what ways. Finally, the baselines of future research in the field of data integration for NDT are drawn.

Synchronous Monitoring of Cement Hydration and Polymer Film Formation Using 1H-Time-Domain-NMR with T 2 Time-Weighted T 1 Time Evaluation: A Nondestructive Practicable Benchtop Method

The interactions between latex and cement are still not completely understood. In this work, we would like to address the temporal changes in cement hardening and latex film formation. For this reason, the hydration process and the film formation were simultaneously monitored. This scientific issue is even more challenging as a nondestructive quantitative analysis of the film formation process is not available yet. Here, we report on simultaneous monitoring of the latex film formation and the phase development in cementitious systems via ¹H-time-domain-NMR for the first time. The obtained results were validated using classical analytical methods, such as in situ X-ray diffraction, X-ray fluorescence (Rietveld analysis), and confocal laser scanning microscopy.