In Situ Quasi-elastic Neutron Scattering Study of the Hydration of Tricalcium Silicate

FitzGerald, Stephen A.; Neumann, D. A.; Rush, J. J.; Bentz, Dale P.; Livingston, Richard A.

doi:10.1021/cm970564a

Cited by 102 publications

(134 citation statements)

References 19 publications

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“…Again the M-values obtained for the cellulose-added pastes reveal a modification in the hydrated phase's morphology, as testified by SEM micrographs (figures 5(D)-(F)). The diffusional constants obtained for pastes of C 3 S in pure water are very similar to those reported in a previous work with neutron scattering, with the same w/c ratio and with similar surface area of the powder [51], further confirming the validity of our method. Several studies showed the K d -values to be independent of temperature [23,51].…”

Section: Nucleation and Growthsupporting

confidence: 87%

“…Diffusion-limited Activation energies interval from 30 to 40 kJ mol −1 , depending on the particle size distribution, is reported [51,57]. The activation energy for this process is not modified when a small amount of MHEC is added to the paste; on the contrary, a ten times higher amount of cellulosic polymer causes a consistent increase of the activation energy, probably due to the a large amount of water strictly bound to the polymer.…”

Section: Nucleation and Growthmentioning

confidence: 95%

“…Each sample formulation was monitored during the whole kinetics at four different temperatures: 10, 20, 30 and 40 • C. Since the t i -values are reported to follow an Arrheniustype behaviour, as a function of temperature, t −1 [51], it was possible to calculate the activation energy for the induction period. Furthermore, by simply applying the Arrhenius equation,…”

Section: State and Dynamics Of The Water Phasementioning

confidence: 99%

“…In these conditions the reaction rate is controlled by the diffusion of species across the gel phase. The relation between degree of reaction (expressed in terms of FWI) and time is the following [43,44,51]:…”

Section: State and Dynamics Of The Water Phasementioning

confidence: 99%

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Hydration water and microstructure in calcium silicate and aluminate hydrates

Fratini

Chen

Baglioni

2006

J. Phys.: Condens. Matter

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Understanding the state of the hydration water and the microstructure development in a cement paste is likely to be the key for the improvement of its ultimate strength and durability. In order to distinguish and characterize the reacted and unreacted water, the single-particle dynamics of water molecules in hydrated calcium silicates (C 3 S, C 2 S) and aluminates (C 3 A, C 4 AF) were studied by quasi-elastic neutron scattering, QENS. The time evolution of the immobile fraction represents the hydration kinetics and the mobile fraction follows a non-Debye relaxation. Less sophisticated, but more accessible and cheaper techniques, like differential scanning calorimetry, DSC, and nearinfrared spectroscopy, NIR, were validated through QENS results and they allow one to easily and quantitatively follow the cement hydration kinetics and can be widely applied on a laboratory scale to understand the effect of additives (i.e., superplasticizers, cellulosic derivatives, etc) on the thermodynamics of the hydration process. DSC provides information on the free water index and on the activation energy involved in the hydration process while the NIR band at 7000 cm −1 monitors, at a molecular level, the increase of the surface-interacting water. We report as an example the effect of two classes of additives widely used in the cement industry: superplasticizers, SPs, and cellulose derivatives. SPs interact at the solid surface, leading to a consistent increment of the activation energy for the processes of nucleation and growth of the hydrated phases. In contrast, the cellulosic additives do not affect the nucleation and growth activation energy, but cause a significant increment in the water availability: in other words the hydration process is more efficient without any modification of the solid/liquid interaction, as also evidenced by the 1 H-NMR. Additional information is obtained by scanning electron microscopy (SEM), ultra small 3 Author to whom any correspondence should be addressed. www.csgi.unifi.it. angle neutron scattering (USANS) and wide angle x-ray scattering (WAXD) that characterize how additives affect both the hydrated microstructure development and the original grain size. In particular, SPs alter the morphology of the hydrated phases, which no longer grow with the classic fibrillar structure on the grain surface, but nucleate in solution as globular structures. All this information converges in a quantitative, and at molecular level, description of the mechanisms involved in the setting process of one of the materials most widely used by human beings.

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Section: Nucleation and Growthsupporting

confidence: 87%

Section: Nucleation and Growthmentioning

confidence: 95%

Section: State and Dynamics Of The Water Phasementioning

confidence: 99%

Section: State and Dynamics Of The Water Phasementioning

confidence: 99%

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Hydration water and microstructure in calcium silicate and aluminate hydrates

Fratini

Chen

Baglioni

2006

J. Phys.: Condens. Matter

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“…For example, the hydration properties of cement have been frequently studied by QENS experiments [2][3][4][5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Direct Observation of Supercooled Water in Mortar Materials by Quasi-elastic Neutron Scattering

Mori

Iwase

Sugiyama

et al. 2012

Trans. Mat. Res. Soc. Japan

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In order to clarify the mechanism of frost damage for concrete materials, we investigated the state of water in a Low Heat Portland Cement (LHPC) mortar at temperatures between T = 282 K and 202 K, using quasi-elastic neutron scattering (QENS). Below the freezing point of water (i.e., T < 273 K), a broad peak for supercooled water in the LHPC mortar was clearly observed on a QENS spectrum. In addition, the supercooled water index (SCWI), which is the ratio of the signal from the supercooled water (SCW) to the signal from the free water at 282 K (FW 282K ) (i.e., SCWI = SCW / FW 282K ), was estimated for each temperature in a freeze-thaw cycle. Consequently, it was found that there is a hysteresis in the SCWI(T) curve; the amount of the supercooled water in the freeze cycle was 1.2-1.4 times larger than that in the thaw cycle at the same temperature.

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Nucleation‐Governed Reversible Self‐Assembly of an Organic Semiconductor at Surfaces: Long‐Range Mass Transport Forming Giant Functional Fibers

Luca

Liscio

Maccagnani

et al. 2007

Adv Funct Materials

108

102

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The use of solvent‐vapor annealing (SVA) to form millimeter‐long crystalline fibers, having a sub‐micrometer cross section, on various solid substrates is described. Thin films of a perylene‐bis(dicarboximide) (PDI) derivative, with branched alkyl chains, prepared from solution exhibit hundreds of nanometer‐sized PDI needles. Upon exposure to the vapors of a chosen solvent, tetrahydrofuran (THF), the needles re‐organize into long fibers that have a remarkably high aspect ratio, exceeding 103. Time‐ and space‐resolved mapping with optical microscopy allows the self‐assembly mechanism to be unravelled; the mechanism is found to be a nucleation‐governed growth, which complies with an Avrami‐type of mechanism. SVA is found to lead to self‐assembly featuring i) long‐range order (up to the millimeter scale), ii) reversible characteristics, as demonstrated through a series of assembly and disassembly steps, obtained by cycling between THF and CHCl3 as solvents, iii) remarkably high mass transport because the PDI molecular motion is found to occur at least over hundreds of micrometers. Such a detailed understanding of the growth process is fundamental to control the formation of self‐assembled architectures with pre‐programmed structures and physical properties. The versatility of the SVA approach is proved by its successful application using different substrates and solvents. Kelvin probe force microscopy reveals that the highly regular and thermodynamically stable fibers of PDI obtained by SVA exhibit a greater electron‐accepting character than the smaller needles of the drop‐cast films. The giant fibers can be grown in situ in the gap between microscopic electrodes supported on SiOx, paving the way towards the application of SVA in micro‐ and nanoelectronics.

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In Situ Quasi-elastic Neutron Scattering Study of the Hydration of Tricalcium Silicate

Cited by 102 publications

References 19 publications

Hydration water and microstructure in calcium silicate and aluminate hydrates

Hydration water and microstructure in calcium silicate and aluminate hydrates

Direct Observation of Supercooled Water in Mortar Materials by Quasi-elastic Neutron Scattering

Nucleation‐Governed Reversible Self‐Assembly of an Organic Semiconductor at Surfaces: Long‐Range Mass Transport Forming Giant Functional Fibers

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