Documents disponibles écrits par cet auteur

Alkali binding in hydrated Portland cement paste / W. Chen in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 716–722 Titre : Alkali binding in hydrated Portland cement paste Type de document : texte imprimé Auteurs : W. Chen, Auteur ; H. J. H. Brouwers, Auteur Année de publication : 2012 Article en page(s) : pp. 716–722 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Alkalis  ;  Hydration  products  ;  Modeling  ;  Pore  solution  ;  Portland  cement Résumé : The alkali-binding capacity of C–S–H in hydrated Portland cement pastes is addressed in this study. The amount of bound alkalis in C–S–H is computed based on the alkali partition theories firstly proposed by Taylor (1987) and later further developed by Brouwers and Van Eijk (2003). Experimental data reported in literatures concerning thirteen different recipes are analyzed and used as references. A three-dimensional computer-based cement hydration model (CEMHYD3D) is used to simulate the hydration of Portland cement pastes. These model predictions are used as inputs for deriving the alkali-binding capacity of the hydration product C–S–H in hydrated Portland cement pastes. It is found that the relation of Na+ between the moles bound in C–S–H and its concentration in the pore solution is linear, while the binding of K+ in C–S–H complies with the Freundlich isotherm. New models are proposed for determining the alkali-binding capacities of C–S–H in hydrated Portland cement paste. An updated method for predicting the alkali concentrations in the pore solution of hydrated Portland cement pastes is developed. It is also used to investigate the effects of various factors (such as the water to cement ratio, clinker composition and alkali types) on the alkali concentrations. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884610000025 [article] Alkali binding in hydrated Portland cement paste [texte imprimé] / W. Chen, Auteur ; H. J. H. Brouwers, Auteur . - 2012 . - pp. 716–722. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 716–722 Mots-clés : Alkalis  ;  Hydration  products  ;  Modeling  ;  Pore  solution  ;  Portland  cement Résumé : The alkali-binding capacity of C–S–H in hydrated Portland cement pastes is addressed in this study. The amount of bound alkalis in C–S–H is computed based on the alkali partition theories firstly proposed by Taylor (1987) and later further developed by Brouwers and Van Eijk (2003). Experimental data reported in literatures concerning thirteen different recipes are analyzed and used as references. A three-dimensional computer-based cement hydration model (CEMHYD3D) is used to simulate the hydration of Portland cement pastes. These model predictions are used as inputs for deriving the alkali-binding capacity of the hydration product C–S–H in hydrated Portland cement pastes. It is found that the relation of Na+ between the moles bound in C–S–H and its concentration in the pore solution is linear, while the binding of K+ in C–S–H complies with the Freundlich isotherm. New models are proposed for determining the alkali-binding capacities of C–S–H in hydrated Portland cement paste. An updated method for predicting the alkali concentrations in the pore solution of hydrated Portland cement pastes is developed. It is also used to investigate the effects of various factors (such as the water to cement ratio, clinker composition and alkali types) on the alkali concentrations. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884610000025

Effect of installation method on external shaft friction of caissons in soft clay / W. Chen in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 5 (Mai 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 5 (Mai 2009) . - pp. 605–615 Titre : Effect of installation method on external shaft friction of caissons in soft clay Type de document : texte imprimé Auteurs : W. Chen, Auteur ; H. Zhou, Auteur ; M. F. Randolph, Auteur Année de publication : 2009 Article en page(s) : pp. 605–615 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Caissons  Centrifuge  models  Clays  Soft  soils  Finite  element  method  Skin  friction Résumé : The influence of the installation method on the soil flow pattern, resulting external radial total stress changes, and final external shaft friction after consolidation has been investigated for caissons in soft clay by means of centrifuge model tests, large deformation finite-element (FE) analysis, and a simple cavity expansion approach. Both the centrifuge measurements and the FE results show that more soil is forced into the caisson under suction than under jacking. However, the difference in the resulting external radial total stress changes or penetration-induced excess pore-water pressure is much less significant, since the expansion-induced excess pore pressure is smaller for thin-walled caissons than for driven piles. After subsequent consolidation, the influence of the installation method reduces further, and the final shaft friction ratios are close for the two installation methods. Based on the magnitude of heave ratios derived from the centrifuge measurements and the FE analysis, a simple form of cavity expansion approach can reasonably estimate external radial stress changes during installation and after consolidation, and final shaft friction ratios for the caissons. An approach for estimating the external shaft friction ratios for vertical pullout of sealed caissons is proposed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000033 [article] Effect of installation method on external shaft friction of caissons in soft clay [texte imprimé] / W. Chen, Auteur ; H. Zhou, Auteur ; M. F. Randolph, Auteur . - 2009 . - pp. 605–615. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 5 (Mai 2009) . - pp. 605–615 Mots-clés : Caissons  Centrifuge  models  Clays  Soft  soils  Finite  element  method  Skin  friction Résumé : The influence of the installation method on the soil flow pattern, resulting external radial total stress changes, and final external shaft friction after consolidation has been investigated for caissons in soft clay by means of centrifuge model tests, large deformation finite-element (FE) analysis, and a simple cavity expansion approach. Both the centrifuge measurements and the FE results show that more soil is forced into the caisson under suction than under jacking. However, the difference in the resulting external radial total stress changes or penetration-induced excess pore-water pressure is much less significant, since the expansion-induced excess pore pressure is smaller for thin-walled caissons than for driven piles. After subsequent consolidation, the influence of the installation method reduces further, and the final shaft friction ratios are close for the two installation methods. Based on the magnitude of heave ratios derived from the centrifuge measurements and the FE analysis, a simple form of cavity expansion approach can reasonably estimate external radial stress changes during installation and after consolidation, and final shaft friction ratios for the caissons. An approach for estimating the external shaft friction ratios for vertical pullout of sealed caissons is proposed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000033

Electrochemical characterization for polybithiophene film on porous oxide layer of 304 stainless steel formed by square wave passivation / C. Liang in Materials and corrosion, Vol. 63 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Materials and corrosion > Vol. 63 N° 2 (Fevrier 2012) . - pp. 155–160 Titre : Electrochemical characterization for polybithiophene film on porous oxide layer of 304 stainless steel formed by square wave passivation Type de document : texte imprimé Auteurs : C. Liang, Auteur ; W. Chen, Auteur ; Huang, N., Auteur Année de publication : 2012 Article en page(s) : pp. 155–160 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Electrochemical  impedance  spectroscopy;  electropolymerization;  polybithiophene;  square  wave  passivation Résumé : A bilayer coating was prepared by electrodepositing a polybithiophene (PBT) film on the top of square wave passivated 304 stainless steel (304SS). The structure of the PBT layer was characterized by FTIR spectroscopy and suggested to be composed of α–α coupling thiophene units. The electrochemical properties of the coating were investigated in 1 mol/L sulfuric acid solution by anodic polarization and electrochemical impedance spectroscopy measurements. The results indicated that the bilayer could provide an effective barrier and maintain the metal substrate in a passive state during the immersion time. The interfacial shear strength of the polythiophene film on untreated and passivated 304SS were 0.81 and 5.1 MPa, respectively. The better result given by treated one may be due to PBT growing within the pores formed on the square wave passivated 304SS. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.200905351/abstract [article] Electrochemical characterization for polybithiophene film on porous oxide layer of 304 stainless steel formed by square wave passivation [texte imprimé] / C. Liang, Auteur ; W. Chen, Auteur ; Huang, N., Auteur . - 2012 . - pp. 155–160. Génie mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 63 N° 2 (Fevrier 2012) . - pp. 155–160 Mots-clés : Electrochemical  impedance  spectroscopy;  electropolymerization;  polybithiophene;  square  wave  passivation Résumé : A bilayer coating was prepared by electrodepositing a polybithiophene (PBT) film on the top of square wave passivated 304 stainless steel (304SS). The structure of the PBT layer was characterized by FTIR spectroscopy and suggested to be composed of α–α coupling thiophene units. The electrochemical properties of the coating were investigated in 1 mol/L sulfuric acid solution by anodic polarization and electrochemical impedance spectroscopy measurements. The results indicated that the bilayer could provide an effective barrier and maintain the metal substrate in a passive state during the immersion time. The interfacial shear strength of the polythiophene film on untreated and passivated 304SS were 0.81 and 5.1 MPa, respectively. The better result given by treated one may be due to PBT growing within the pores formed on the square wave passivated 304SS. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.200905351/abstract