Ab Initio Calculations for the Substitutions of Al(OH)-4 and SO2-4with Si Tetrahedra.

Rahman, Md. Mazibur; Nagasaki, Shinya; Tanaka, Satoru

doi:10.3327/jnst.38.533

Cited by 6 publications

(7 citation statements)

References 19 publications

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“…Note that the stability of the silicate chains has not been addressed in previous studies that focused on using either pair potentials 8 or ab initio calculations. 11,12,25,26 In Fig. 5͑b͒, the stability index, S͑m͒, is depicted ͑solid line͒ as a function of m. The local maxima of S͑m͒ happen at m = 2, 5, and 8, showing that these are the most stable configurations in the analyzed range.…”

Section: A Condensation Reactions and Chain Stabilitymentioning

confidence: 97%

Silicate chain formation in the nanostructure of cement-based materials

Ayuela

Dolado²,

Campillo³

et al. 2007

The Journal of Chemical Physics

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Cement-based materials are ubiquitous in almost all built environment. In spite of this, little is known about the formation and the role played by the silicate chains always present in the cement nanostructure. By means of first principles simulations we provide compelling evidence on the pivotal role played by certain ionic species in the formation of the silicate chains inside the cementitious matrix. Moreover, we corroborate the experimental evidence which shows that the length of the most stable chains with m Si atoms follows a magic-number sequence: m =3n − 1 with n =1,2,... Our results have been applied in the development of new higher performance cement-based materials by adding nanosilica.

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Section: A Condensation Reactions and Chain Stabilitymentioning

confidence: 97%

Silicate chain formation in the nanostructure of cement-based materials

Ayuela

Dolado²,

Campillo³

et al. 2007

The Journal of Chemical Physics

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“…The substitution of Si by Al is reported in the cement hydration phases. [11,30,45,46] Similarly, the substitution of Ca 2ϩ (ionic radius r Ca2ϩ(hydrated) ϭ 1.08 nm) by Mg 2ϩ ions (ionic radius r Mg2ϩ(hydrated) ϭ 0.96 nm) is expected, based on the ionic radii and valency state considerations. Hence, we choose to calculate the [(Ca ϩ Mg)/(Si ϩ Al)] ratio along with the Ca/Si ratio.…”

Section: Characterization Of the Hydration Product By Temmentioning

confidence: 98%

Hydration of mechanically activated granulated blast furnace slag

Kumar

Badjena

et al. 2005

Metall Mater Trans B

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Ground granulated blast furnace slag (GGBFS) is known to possess latent hydraulic activity, i.e., it shows cementitious properties when in contact with water over a long period of time. Results are presented in this article to show that, in sharp contrast to published literature on the hydration of neat GGBFS, the complete hydration of slag is possible in a short time (days), even without a chemical activator. This is achieved if the slag used for hydration is mechanically activated, using an attrition mill. The nature of the hydration product of the mechanically activated slag depends not only on the initial specific surface area (SSA) of the slag but also on the surface activation, as manifested by the change in the zeta potential () of the slag during the milling process. Depending upon the SSA and the , the hydration product changed from nonreacted slag with high porosity (slag SSA Ͻ 0.3 m 2 /g, Ͼ Ϫ29 mV) to hydrated slag with a compact structure (SSA ϭ 0.3 to 0.4 m 2 /g, ϭ Ϫ29 to Ϫ31 mV), and, finally, to fully hydrated slag with high porosity (SSA Ͼ 0.4 m 2 /g, ϳ 26 mV). Unlike the poorly crystalline hydration product formed by the nonactivated slag, even after prolonged hydration for years, the hydration product of mechanically activated slag was crystalline in nature. The crystallinity of the product improved as the duration of the mechanical activation increased. The calciumsilicate-hydrate (C-S-H) phases present in the slag hydration product, characterized by a Ca/Si ratio of 0.7 to 1.5, were similar to those found for the hydraulic cement binder, except for the presence of Mg and Al as impurities. In addition, the presence of a di-calcium-silicate-hydrate phase (␣-C 2 SH), which normally forms under hydrothermal conditions, and a Ca-deficient and Si-Al-rich phase (average Ca/Si mole ratio Ͻ0.1 and Si/Al ϳ 3) is indicated, especially in the hydration product of slag that was activated for a longer time.

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“…In particular, resonances in the range from 55 to 80 ppm correspond to tetra-coordinated aluminium Al[4] at tetrahedral (T d ) sites, whereas those in the range from À5 to 20 ppm are originated from Al [5] and Al[6] (pentaand hexa-coordinated) at octahedral (O h ) sites (Kirkpatrick and Cong, 1994;Manzano et al, 2009b;Müller et al, 1977Müller et al, , 1981Rahman et al, 2001;Schneider et al, 2001). 27 Al NMR spectra obtained for L100-0, L100-6 and L100-18 ( Figure 8) show both types of resonances but with very different intensities.…”

Section: Nuclear Magnetic Resonance (Nmr) Spectroscopymentioning

confidence: 99%

“…However, the reduction in the intensity of the peak at 8 . 5 ppm suggests a reaction between the nanosilica and the aluminate phases during the hydration process to produce Al substituted calcium-silicate-hydrate gel (Kirkpatrick and Cong, 1994;Manzano et al, 2009b;Qomi et al, 2012;Rahman et al, 2001;Schneider et al, 2001).…”

Section: Nuclear Magnetic Resonance (Nmr) Spectroscopymentioning

confidence: 99%

Multi-scale analysis of cement pastes with nanosilica addition

Bustos

Gaitero

Quiñones

et al. 2014

Advances in Cement Research

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The effect of the addition of nanosilica on the properties of cement pastes after 28 d of hydration was studied in a multi-scale approach through X-ray diffraction, thermal analysis, nitrogen adsorption analysis, infrared spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and compressive strength tests. The results showed an increase in strength resulting from the pozzolanic nature of the nanosilica, the reduction and refinement of the paste porosity and also the increase of the of calcium-silicate-hydrate gel polymerisation with the addition. Furthermore, NMR spectra suggested that the presence of nanosilica produces an inclusion of the Al 3 ion in the gel structure.

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Ab Initio Calculations for the Substitutions of Al(OH)-4 and SO2-4with Si Tetrahedra.

Cited by 6 publications

References 19 publications

Silicate chain formation in the nanostructure of cement-based materials

Silicate chain formation in the nanostructure of cement-based materials

Hydration of mechanically activated granulated blast furnace slag

Multi-scale analysis of cement pastes with nanosilica addition

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