scholarly journals Porous and adsorption properties of hydrated cement paste

2004 ◽  
Vol 58 (1) ◽  
pp. 6-9 ◽  
Author(s):  
Biljana Marina ◽  
Snezana Brezovska ◽  
Donco Burevski ◽  
Biljana Panova
Keyword(s):  
Mechanical Properties ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Adsorption Isotherms ◽  
Favorable Effect ◽  
Hydrated Cement ◽  
Free Energy Of Adsorption ◽  
Characteristic Energy ◽  
Cement Pastes ◽  
Hydrated Cement Paste

Adsorption isotherms of benzene on hydrated cement pastes prepared by cement ground with and without the addition of grinding aids, triethanol amine (TEA) and ethylene glycol (EG) were investigated. The adsorption isotherms were interpreted by means of the Dubinin-Astakhov (DA) and Dubinin-Radushkevich-Stoeckli (DRS) equations. The microporous structure of cement gel (C-S-H) in the cement pastes, and changes in the Gibbs free energy of adsorption were determined. The mechanical properties of the cement pastes were also measured. It was evident that pastes with additives had different parameters of the DRS and DA equations: the volume and dimensions of the gel pores, the distribution of the dimensions, the characteristic energy of adsorption, and the change in the Gibbs free energy of adsorption. The mechanical properties were also different. The dispersity of the additive-containing ground cements had a favorable effect on the hydration processes. When applying TEA, it was also necessary to analyze its influence on the chemical behavior of hydration in the starting period.

scholarly journals The adsorption characteristics and porous structure of bentonite adsorbents, determined from the adsorption isotherms of benzene vapor

2004 ◽  
Vol 69 (2) ◽  
pp. 145-151 ◽  
Author(s):  
Snezana Brezovska ◽  
Biljana Marina ◽  
Biljana Panova ◽  
Donco Burevski ◽  
Vasa Bosevska ◽  
...  
Keyword(s):  
Free Energy ◽  
Porous Structure ◽  
Pore Size ◽  
Adsorption Isotherms ◽  
Micropore Volume ◽  
Benzene Vapor ◽  
Free Energy Of Adsorption ◽  
Volume Filling ◽  
Activated Bentonite ◽  
Characteristic Values

The adsorption of benzene vapor on natural and acid activated bentonites was treated by the theory of volume filling of micropores. The micropore volume and characteristic values of the free energy of adsorptionwere determined from the adsorption isotherms. The Dubinin?Radushkevish?Stoeckli and Dubinin?Astakhov equations were used for this purpose. The results showed that natural bentonite has a more homogeneous micropore structure than the acid activated ones. The characteristic values of the free energy of adsorption for the natural bentonite were higher than those of the acid activated bentonite. This is due to differences in its structure and the pore size.

Entropy of Nanostructures

2017 ◽  
pp. 600-614
Author(s):  
Ottorino Ori ◽  
Franco Cataldo ◽  
Mihai V. Putz
Keyword(s):  
Mechanical Properties ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Defect Formation ◽  
Vacancy Concentration ◽  
Structural Evolution ◽  
Point Of View ◽  
Structural Defects ◽  
Formation Mechanisms ◽  
Topological Invariants

Recent advances in graphene studies deal with the influence of structural defects on graphene chemical, electrical, magnetic and mechanical properties. Here the complex mechanisms leading to the formation of clusters of vacancies in 2D honeycomb HD lattices are described by a pure topological point of view, aiming to correlate the variation of specific topological invariants, sensible to vacancy concentration, to the structural evolution of the defective networks driven by the topo-thermodynamical Gibbs free energy. Interesting predictions on defect formation mechanisms add details on the topological mechanisms featured by the graphenic structures with defects. Future roles of bondonic particles in defective HD materials are also envisaged.

Microstructure of fly ash containing concrete, with emphasis on the aggregate-paste boundary

1993 ◽  
Vol 51 ◽  
pp. 1148-1149 ◽  
Author(s):  
Marcelle A. Gillott ◽  
Tarun R. Naik ◽  
Shiw S. Singh
Keyword(s):  
Fly Ash ◽  
Interfacial Region ◽  
Hydrated Cement ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Design Strength ◽  
Cement Pastes ◽  
Coarse Aggregates ◽  
Hydrated Cement Paste ◽  
Concrete Mixtures

Concrete is a highly heterogeneous structural material that is subjected to complex stresses. It has been well established that concrete is weakest in the interfacial region between coarse aggregates and the hydrated cement paste. Although there have been several studies on the microstructure of fly ash containing cement pastes, relatively less is known about the effect of fly ash on the aggregate-paste boundary in concrete.Air entrained plain portland cement concrete mixtures were prepared to produce a design strength of 6000 psi at the 28-day age. The air and H2O-cementitious ratios were held approximately constant for both the control and fly ash containing preparations. ASTM Class C fly ash replaced 15% to 70% of the cement in various samples. Measurement of mechanical properties indicated compressive strength increased for concrete with up to 30% fly ash; only slight differences in tensile strength were observed among the control, 15% and 30% fly ash replacements.

Toward Accurate and Efficient Predictions of Entropy and Gibbs Free Energy of Adsorption of High Nitrogen Compounds on Carbonaceous Materials

2014 ◽  
Vol 118 (9) ◽  
pp. 4774-4783 ◽  
Author(s):  
Andrea Michalkova Scott ◽  
Leonid Gorb ◽  
Elizabeth A. Burns ◽  
Sergey N. Yashkin ◽  
Frances C. Hill ◽  
...  
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Nitrogen Compounds ◽  
Carbonaceous Materials ◽  
High Nitrogen ◽  
Free Energy Of Adsorption

Small-Angle Neutron Scattering from Hydrated Cement Pastes

1994 ◽  
Vol 376 ◽  
Author(s):  
L.P. Aldridge ◽  
W.K. Bertram ◽  
T.M. Sabine ◽  
J Bukowski ◽  
J.F. Young ◽  
...  
Keyword(s):  
Data Analysis ◽  
Neutron Scattering ◽  
Cement Paste ◽  
Small Angle ◽  
Calcium Silicate ◽  
Small Angle Neutron Scattering ◽  
Calcium Silicate Hydrate ◽  
Hydrated Cement ◽  
Cement Pastes ◽  
Hydrated Cement Paste

ABSTRACTSmall angle neutron scattering (SANS) has been used to examine hydrated cement pastes with water-to-cement ratios between 0.25 and 0.8 and cured for 28 days. Various methods of data analysis are applied to the pastes.Fitting the entire SANS spectra of the hydrated cement paste has suggested that there are two scattering entities in the paste. There is some evidence to suggest that one scattering entity is globules of calcium silicate hydrate formed in the hydrated paste.

scholarly journals Adsorption properties and porous structure of sulfuric acid treated bentonites determined by the adsorption isotherms of benzene vapor

2005 ◽  
Vol 70 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Snezana Brezovska ◽  
Biljana Marina ◽  
Donco Burevski ◽  
Biljana Angjuseva ◽  
Vasa Bosevska ◽  
...  
Keyword(s):  
Free Energy ◽  
Sulfuric Acid ◽  
Adsorption Isotherms ◽  
Structural Changes ◽  
Micropore Volume ◽  
Benzene Vapor ◽  
Structural Parameter ◽  
Acid Activation ◽  
Free Energy Of Adsorption ◽  
Differential Distribution

In a previous paper, adsorption isotherms of benzene vapor on natural bentonite from Ginovci, Macedonia, and forms acid activated with 10% and 15% solutions of hydrochloric were interpreted by means of the Dubinin-Radushkevich-Stoeckli and Dubinin-Astakhov equations; the investigation has been continued with bentonites acid activated with 10% and 15% solutions of sulfuric acid where X-ray analysis indicates smaller structural changes. Using the above equations, the heterogeneity of the micropores and the energetic heterogeneity of the bentonites were determined from the differential distribution of the micropore volume with respect to the structural parameter of the equations characterizing the microporous structure and to the molar free energy of adsorption. Activated bentonites obtain bigger pores but also a certain quantity of new small pores appear during acid activation with the higher concentration of acid. The micropore volumes, determined from the adsorption of benzene vapor, of bentonites activated with 10 % and 15 % solution of hydrochloric acid (144.60 cm3 kg-1 and 110.06 cm3 kg-1, respectively), decrease in comparison with that of natural bentonite (162.55 cm3 kg-1). In contrast, the values of the micropore volume for bentonities treated with 10 % and 15 % solutions of sulfuric acids increase (169.19 cm3 kg-1 and 227.74 cm3 kg-1). That is due to the difference in the structural changes occurring during activation with hydrochloric and sulfuric acids. The values of the free energy of adsorption of benzene vapor for natural bentonite are higher than those of the acid activated bentonities, what is in accordance with the structural and porosity changes.

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