Aluminum-induced dreierketten chain cross-links increase the mechanical properties of nanocrystalline calcium aluminosilicate hydrate

Abstract

The incorporation of Al and increased curing temperature promotes the crystallization and cross-linking of calcium (alumino)silicate hydrate (C-(A-)S-H), which is the primary binding phase in most contemporary concrete materials. However, the influence of Al-induced structural changes on the mechanical properties at atomistic scale is not well understood. Herein, synchrotron radiation-based high-pressure X-ray diffraction is used to quantify the influence of dreierketten chain cross-linking on the anisotropic mechanical behavior of C-(A-)S-H. We show that the ab-planar stiffness is independent of dreierketten chain defects, e.g. vacancies in bridging tetrahedra sites and Al for Si substitution. The c-axis of non-cross-linked C-(A-)S-H is more deformable due to the softer interlayer opening but stiffens with decreased spacing and/or increased zeolitic water and Ca2+ of the interlayer. Dreierketten chain cross-links act as ‘columns’ to resist compression, thus increasing the bulk modulus of C-(A-)S-H. We provide the first experimental evidence on the influence of the Al-induced atomistic configurational change on the mechanical properties of C-(A-)S-H. Our work advances the fundamental knowledge of C-(A-)S-H on the lowest level of its hierarchical structure, and thus can impact the way that innovative C-(A-)S-H-based cementitious materials are developed using a ‘bottom-up’ approach.

Effects of CO2 and temperature on the structure and chemistry of C–(A–)S–H investigated by Raman spectroscopy

“…In addition, cement hydration products can be analyzed effectively and relatively quickly with no extra sample preparation steps needed. 16 The sensitivity of this technique enables the analysis of poorly crystalline/amorphous carbonate phases that precipitate on the surface of C-(A-)S-H samples exposed to CO 2 .…”

“…Understanding the structural properties of C-(A-)S-H provides insight into the physical and mechanic behavior of the cement based materials. 15,16 The synthesis temperature is an important parameter affecting key properties such as, density, chemical composition, microstructure and compressive strength of cement based materials. 12,17 Moreover, due to the exothermical hydration reactions, concrete structures may experience signicant temperature rise when used in large volume, e.g.…”

In situ full view of the Portland cement hydration by confocal Raman microscopy

“…Nevertheless, stopping the reaction process can affect the main reaction products that are generated after the hydration of Portland cement, such as ettringite, phases, portlandite, or the C‐S‐H gel . In situ analysis of the reactions at earlier ages is usually restricted to large facilities as synchrotron . Additionally, the microstructural information is elusive, and the kinetic implications are difficult to be evaluating in direct experimental setups.…”

“…Over time, the study of cement‐based materials focused on the different tests of mixing and breaking of prismatic specimens to evaluate its mechanical resistance. The determination of the structural properties has been carried out in combination with numerous analytical methodologies and numerous conventional characterization techniques: X‐ray diffraction (XRD), differential thermal and thermogravimetric analysis (DTA‐TG), Fourier‐transform infrared (FTIR), Raman spectroscopy, NMR, Syncrotron, dielectric monitoring, and so forth. These techniques provided valuable information to better understand the existing mechanisms involved in cement hydration processes.…”

Mechanistic insight into mineral carbonation and utilization in cement-based materials at solid–liquid interfaces

“…) in the presence of minor components such as sulfates and carbonates. In order to elucidate the hydration reactions of different types of Portland cements, great efforts have been made on applying the advanced analytical techniques, such as in situ X-ray diffraction, 15 high-pressure X-ray diffraction, 16,17 X-ray absorption near edge structure spectrometry 18 and nanoscale tomography. 19 These studies could provide signicant impacts on modeling the kinetics and morphological evolution of cement hydration.…”