Mechanism of aluminium incorporation into C–S–H from ab initio calculations

2014 ◽  
Vol 2 (10) ◽  
pp. 3477-3483 ◽  
Author(s):  
Luís Pegado ◽  
Christophe Labbez ◽  
Sergey V. Churakov
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Cementitious Materials ◽  
Al Substitution

Al substitution in calcium silicate hydrate (C–S–H) in novel, low CO2 cementitious materials takes place in bridging tetrahedral positions only.

Micromechanical Properties of Calcium Silicate Hydrate

2013 ◽  
Vol 539 ◽  
pp. 75-79
Author(s):  
Wu Yao ◽  
Li He
Keyword(s):  
Fly Ash ◽  
Reaction Zone ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Cement Hydration ◽  
Cementitious Materials ◽  
Pozzolanic Reaction ◽  
Indentation Modulus ◽  
Micromechanical Properties ◽  
Secondary Hydration

The indentation modulus of several cementitious materials is discussed with the assumption that the C-S-H gel is an aggregation of precipitated, colloidal-sized particles. At least two kinds of structurally distinct but compositional similar phases are found existent during the hydration process. In addition, the C-S-H originated from the pozzolanic reaction of fly ash is found to be the same to that of cement hydration in micromechanical properties; however, the C-S-H gel formed from the secondary hydration is inclined to develop into high density packing configuration, due to the limitation of reaction zone available.

Xonotlite and Hillebrandite as Model Compounds for Calcium Silicate Hydrate Seeding in Cementitious Materials

2020 ◽  
pp. 036119812094320
Author(s):  
Elisabeth John ◽  
Christian Lehmann ◽  
Dietmar Stephan
Keyword(s):  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Model Compound ◽  
Hydration Product ◽  
Cementitious Materials ◽  
Nucleation Site ◽  
Hydration Products ◽  
Sem Images ◽  
Pit Formation ◽  
Nanoparticle Additives

The demand for more environmentally friendly cement with no disadvantages in relation to hydration activity has led to the development of various additives to accelerate cement hydration. As calcium silicate hydrate (C-S-H) is the major hydration product of cement and is responsible for its mechanical properties, it plays an outstanding role in the discussion of nanoparticle additives. Nevertheless, the investigation of its mechanism of action is complicated by the similarity of its properties to those of the C-S-H that forms as an initial hydration product. Crystalline C-S-H phases, on the other hand, can be easily distinguished from the original hydration products, which makes them a valuable model compound for studying the mechanisms of nucleation seeding in cementitious materials. In this paper, the effect of crystalline types of C-S-H as nucleation seeds are presented. Xonotlite and hillebrandite were thoroughly characterized using nuclear magnetic resonance, X-ray diffractometry (XRD), scanning electron microscopy (SEM), and infrared spectroscopy (IR) and were then used as an admixture for alite pastes. Low-vacuum SEM images of the hydrated pastes revealed that xonotlite can significantly promote the visible etch pit formation on C3S clinker particles, which was not found to be true for hillebrandite. Whether the phases act as a nucleation site is assumed to be strongly dependent on the mineralogy: hillebrandite appeared to be heavily overgrown, but xonotlite did not show any hydration products on its surfaces after the same hydration time of up to 24 h. The diverse effect of the minerals was confirmed by the accelerating behavior in isothermal heat flow calorimetry and by XRD.

scholarly journals Ionic conductive and photocatalytic properties of cementitious materials: calcium silicate hydrate and calcium aluminoferrite

2020 ◽  
Vol 8 (30) ◽  
pp. 15157-15166
Author(s):  
Masahiro Nagao ◽  
Kazuyo Kobayashi ◽  
Yongcheng Jin ◽  
Ippei Maruyama ◽  
Takashi Hibino
Keyword(s):  
Photocatalytic Activity ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Concrete Structures ◽  
Cementitious Materials ◽  
Ion Conductivity ◽  
Photocatalytic Properties ◽  
Calcium Aluminoferrite ◽  
The Stability

Ion conductivity of C-S-H and photocatalytic activity of C4AF for the stability of concrete structures and the functionality of concrete surfaces.

scholarly journals Effect of Water on the Dynamic Tensile Mechanical Properties of Calcium Silicate Hydrate: Based on Molecular Dynamics Simulation

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2837 ◽  
Author(s):  
Jikai Zhou ◽  
Yuanzhi Liang
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Water Content ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Cementitious Materials ◽  
Constitutive Relationship ◽  
Degree Of Saturation ◽  
Strain Rates ◽  
Effect Of Water

To study the effect of water on the dynamic mechanical properties of calcium silicate hydrate (C–S–H) at the atomic scale, the molecular dynamics simulations were performed in uniaxial tension with different strain rates for C–S–H with a degree of saturation from 0% to 100%. Our calculations demonstrate that the dynamic tensile mechanical properties of C–S–H decrease with increasing water content and increase with increasing strain rates. With an increase in the degree of saturation, the strain rate sensitivity of C–S–H tends to increase. According to Morse potential function, the tensile stress-strain relationship curves of C–S–H are decomposed and fitted, and the dynamic tensile constitutive relationship of C–S–H considering the effect of water content is proposed. This reveals the strain rate effect of the cementitious materials with different water content from molecular insights, and the dynamic constitutive relationship obtained in this paper is necessary to the modelling of cementitious materials at the meso-scale.

Evaluation of Sorption Behavior of Iodide Ions on Calcium Silicate Hydrate and Hydrotalcite

2015 ◽  
Vol 1744 ◽  
pp. 29-34
Author(s):  
Taiji Chida ◽  
Jun Furuya ◽  
Yuichi Niibori ◽  
Hitoshi Mimura
Keyword(s):  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Solid Phase ◽  
Pure Water ◽  
Weight Ratio ◽  
Cementitious Materials ◽  
Sorption Behavior ◽  
Nacl Solution ◽  
Iodide Ions ◽  
Engineered Barriers

ABSTRACTThe migration retardation of anionic radionuclides, notably I-129, in radioactive waste repositories is one of the most critical factors for improving the performance of engineered barriers. To gain more fundamental knowledge required to make such improvements, this study examined the sorption behavior of iodide ions on calcium silicate hydrate (CSH) and hydrotalcite (HT), which act as anion exchangers. CSH was synthesized using CaO and fumed silica, with Ca/Si molar ratios ranging from 0.4 to 1.6. The weight ratio of CSH to HT was 1.0. These solid samples were immersed for 14 days in a 30 mL sample of pure water or 0.6 M NaCl solution, each of which contained 0.5 mM iodide ions with a given liquid/solid weight ratio (10, 15, or 20). Raman spectroscopy studies indicated that the structures of CSH and HT were maintained during the hydration of the solid phase and the sorption of iodide ions. The distribution coefficients for the sorption of iodide ions on CSH and HT ranged from 6 to 13 L/kg for pure water and from 1 to 2 L/kg for NaCl solution. These retardation effects for iodide ions would contribute toward improving the performance of the repository system as most conventional safety assessments assume that iodide ions hardly sorb on engineered barriers such as cementitious materials.

Mechanical properties of calcium silicate hydrate under uniaxial and biaxial strain conditions: A molecular dynamics study

2021 ◽  
Author(s):  
Yongming Tu ◽  
Pan Shi ◽  
Dongyun Liu ◽  
Rongjia Wen ◽  
Qian Yu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Hydration Product ◽  
Cementitious Materials ◽  
Complex Stress ◽  
Biaxial Strain ◽  
Practical Applications ◽  
Reactive Molecular Dynamics ◽  
Molecular Dynamics Methods

Calcium silicate hydrate (C-S-H) is the main hydration product of cementitious materials, often experiencing complex stress conditions in practical applications. Therefore, reactive molecular dynamics methods were used to investigate the...

Millimetre-wave and infrared spectroscopy of Br13 CN: anharmonic force field of cyanogen bromide from spectroscopic data and ab initio calculations

1997 ◽  
Vol 90 (3) ◽  
pp. 495-497
Author(s):  
CLAUDIO ESPOSTI ◽  
FILIPPO TAMASSIA ◽  
CRISTINA PUZZARINI ◽  
RICCARDO TARRONI ◽  
ZDENEK ZELINGER
Keyword(s):  
Infrared Spectroscopy ◽  
Force Field ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Spectroscopic Data ◽  
Cyanogen Bromide ◽  
Millimetre Wave ◽  
Anharmonic Force
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