Formation of the C-S-H Layer during early hydration of tricalcium silicate grains with different sizes

Portland cement is a mixture of solid phases which all react with water. Tricalcium silicate (Ca3SiO5) is its main component and is often used in model systems to study cement hydration. It is generally recognized that setting and hardening of cement are due to the formation, by a dissolution-precipitation process, of a calcium silicate hydrate (C-S-H) on anhydrous grains during Ca3SiO5 hydration. The purpose of this paper is to study the effect of Ca3SiO5 particle size on the nucleation-growth process of C-S-H. An experimental study of the rate of hydration by using different grain sizes under controlled conditions has been performed. The experimental data have been compared with results obtained by numerical simulation based on a particles-aggregation model. The thickness of the C-S-H layer when the reaction becomes limited by diffusion has been then estimated.     

Effect of ternesite on the hydration and properties of calcium sulfoaluminate cement

Journal of Thermal Analysis and Calorimetry - Ternesite is an intermediate phase formed during clinkering of calcium sulfoaluminate (CSA) cement. This paper presents an experimental study on the...     

Effect of moisture on the dielectric properties of porous alumina films

The dielectric properties of porous anodic Al₂O₃ film can change significantly with the adsorption of moisture by the film. This phenomenon can explain the large variations in capacitance and resistance of the Al₂O₃ humidity sensors observed experimentally.In this paper, we propose a theory of the sensor based on the structure of the porous dielectric, the adsorption mechanisms and the effect of semi-conducting inclusions in an insulator. We show that the sensor characteristics are controlled by the macropores in the porous Al₂O₃ film. The role of incipient pores and intercrystallite regions is of secondary importance. The theoretical capacitance and resistance characteristics computed from this analysis agree well with the experimental behaviour.     

Effect of droplet size on the dielectric properties of PDLC films

Polymer dispersed liquid crystal (PDLC) films (5CB/PMMA, 60/40) of different droplet size were prepared by a solvent-induced phase separation method under different N₂ flow speeds. The effects of droplet size on the thermal transitions of the LC and various dielectric properties such as dielectric constant, conductance, dielectric loss, and the electric field induced in a droplet were examined. The configuration of the LC in the film with smaller droplets can be identified by comparing the dielectric constant of the film with the one predicted by Boettcher's mixture formula. In addition, the effect of droplet size on the electro-optical response of the PDLC film was investigated. Variations of the conductance and the dielectric constant of the film were analyzed under various AC frequencies, with the purpose of elucidating the polarization mechanism of the LC molecules in the droplet. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1373–1381, 1997     

Effect of shape on the dielectric properties of biological cell suspensions

In this note, we analyze the effect of cell shape on the dielectric and conductometric behavior of biological cell suspension, in a frequency range where the interfacial polarization characteristic of highly heterogeneous systems occurs. We consider two different families of curves, both of them capable of generating a variety of symmetric or asymmetric shapes, ranging from oval, to dog-bone like, to lemniscate curves. These curves, which differ from those generally employed in dielectric models of biological cell suspensions, describe in principle different cells including discocytes, cup-shaped cells, pear-shaped cells, dumbbells and cells with spherical protrusions or invaginations. Our analysis, based on a numerical solution of the Laplace equation by means of boundary element methods, is carried out in the attempt of separating the contributions associated with the different electrical properties of the dielectric media involved from the ones mainly associated with the shape of the cell. We determine the dielectric strength of the dielectric dispersion for a variety of cell shapes and the phenomenological correlation between this parameter of the relaxation and the cell geometry is briefly discussed and commented.     

Effect of metakaolin structure on its binding properties in alkaline hydration

Aluminum ion coordination to oxygen in metakaolin of different origin was studied by a solid-state ²⁷Al NMR spectroscopy, as well as changes in aluminum ion coordination in an interaction of metakaolins with sodium silicate solution. At the same time a durability of structures resulting from this interaction was examined. Based on the findings the relationship between the structure of metakaolin and its astringent properties in alkaline environment was considered.     

Effect of polycarboxylate type of super plasticizer on the hydration properties of composite cements

The work aims to study the effect of polycarboxylate type of super plasticizer on the hydration of composite cements. In this paper we have studied the hydration of 20 wt% fly ash (FA) blended Portland cement in the presence of 0.1 wt% super plasticizer (SP). Water consistency, setting times, non-evaporable water contents, compressive strength, water percolation, and air content measurements were carried out. In addition, X-ray diffraction studies were carried out to understand the hydration process. The results indicated the increase in compressive strength of the FA blended Portland cement in the presence of SP and with the increase of the hydration time.     

Unusual hydration behavior of dielectric loss in KA zeolite

Two relaxations measured in dehydrated KA zeolite showed different hydration behaviors; the higher frequency relaxation shifted to higher frequency with increasing hydration whereas the lower frequency relaxation shifted to lower frequency; the latter behavior being contrary to present theory.     

Effect of iron on mineral composition of quaternary phase clinker and its hydration properties

Journal of Thermal Analysis and Calorimetry - The present task is to investigate the influence of iron on the mineral composition and microstructure of the phase Q (C20A13M3S3, in the text below...     

Beyond the first hydration shell: dielectric study of LiCl aqueous solution

The dielectric constant for lithium chloride (LiCl) in aqueous solution with the entire concentration has been determined in the frequency range 0.5 GHz–50GHz at 298 K by dielectric relaxation spectroscopy (DRS). The system behaviour is described according to the Cole–Cole and two Debye-type relaxation functions whose evolution with composition is analysed. Combining the Cole–Cole and two Debye-type relaxation functions, the results of the dielectric properties of aqueous LiCl solution are presented and discussed. The maximum number of water molecules perturbed by ions in the hydration shell decays with its concentration. Using the extended Froehlich theory, it is concluded that the water structure is perturbed by ions beyond the first hydration shell in LiCl aqueous solution system.     

Studies on dielectric properties of polymethylacrylate

Colloid and Polymer Science - The behaviors of the two dielectric absorptions for polymethyl acrylate were measured over a wide range of frequency and temperature. The temperature dependences of...     

Effect of sol–gel synthesis conditions on the physical properties of silica hydrogels

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Effect of pulverization of the bulk powder on the hydration of creatine anhydrate tablets and their pharmaceutical properties

The hydration behavior and expansion properties of untreated and pulverized creatine anhydrate (CRA) tablets were studied under 60 and 75%RH at 25 degrees C by using differential scanning calorimetry (DSC), and powder X-ray diffraction (PXRD). The tablet hardness of untreated and pulverized CRA tablets was significantly decreased after hydration. There was a linear relationship between the degree of hydration and the tablet hardness of untreated CRA tablets compressed at 1000 kg/cm2. In contrast, the relationship between the degree of hydration and the tablet hardness of pulverized CRA tablets was nonlinear. These results suggest that the reduction in hardness of pulverized CRA tablets does not depend solely on the hydration level of crystal water. PXRD analysis indicated that the diffraction pattern of the pulverized CRA powder was similar to that of the untreated CRA powder. However, the diffraction intensity of the pulverized CRA powder was slightly lower than that of the untreated CRA powder at high angle. The micropore radius of both untreated and pulverized CRA tablets was significantly increased after hydration, but analysis of the relationship between micropore radius and fractional hydration of crystal water showed that untreated CRA tablets were more affected than pulverized CRA tablets. Therefore, the reduction in tablet hardness depends not only on the hydration behavior but also on the crystal orientation of the CRA powder.     

Effect of ZnO on the hydration of Portland cement

ZnO added to the system Portland cement — water changes the kinetics of the hydration process substantially. Amorphous zinc hydroxide is formed and inhibits the reaction of tricalcium silicate with water, resulting in an induction period prolongation. This effect depends on the amount of ZnO added to the hydrated paste. The transformation of zinc hydroxide into calcium hydrozincate provokes the further hydration.

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Zusammenfassung Durch den Zusatz von ZnO zum System Portlandzement-Wasser wird die Kinetik des Hydratationsprozesses grundlegend verändert. Amorphes Zinkhydroxid wird gebildet, was einen Inhibitor für die Tricalciumsilikatreaktion mit Wasser darstellt, wodurch die Induktionsperiode verlängert wird. Dieser Effekt hängt von der Menge ZnO ab, die dem Zementbrei zugesetzt wurde. Die Umwandlung von Zinkhydroxid zu Calciumhydrozinkat führt eine weitere Hydratation herbei.

     

Effect of reaction conditions on the hydration of isoprene

Effect of conditions (partial pressure of isoprene, temperature, catalyst concentration, medium) on the rate and selectivity of reactions occurring in interaction of isoprene with water in the presence of orthophosphoric acid as a catalyst was studied at elevated temperatures and pressures in the liquid phase. The reaction orders with respect to isoprene were determined for reactions in which 3-methylbutanone-2,2-methylbutanal, and 2,2-dimethylpropanal are formed. The applicability of various acidity characteristics for describing the rates of the reactions under study are considered.     

Protein hydration and volumetric properties

Pressure effects on proteins stem from volumetric differences between their conformational states. These differences implicate rigid structure-based solvent excluded void volumes, although hydration and thermal expansivity differences between states may also play a role. Defining quantitatively the contributions of hydration and solvent excluded voids to protein volumetric properties and thermal expansivities remains a major challenge. Experimental information concerning thermal expansivity can be gained from pressure perturbation calorimetric studies (PPC). We review here recent results from PPC that suggest that while hydration plays a significant role in the volumetric properties of unfolded states of proteins, the volumetric properties of folded states are defined by structural and energetic properties of the folded chain.