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Determining the water–cement ratio, cement content, water content and degree of hydration of hardened cement paste: Method development and validation on paste samples / H.S. Wong in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 957–965 Titre : Determining the water–cement ratio, cement content, water content and degree of hydration of hardened cement paste: Method development and validation on paste samples Type de document : texte imprimé Auteurs : H.S. Wong, Auteur ; N. R. Buenfeld, Auteur Année de publication : 2009 Article en page(s) : pp. 957–965 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Backscattered  electron  imaging  ;  Image  analysis  ;  Microstructure  ;  SEM  ;  w/c  ratio Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : We propose a new method to estimate the initial cement content, water content and free water/cement ratio (w/c) of hardened cement-based materials made with Portland cements that have unknown mixture proportions and degree of hydration. This method first quantifies the composition of the hardened cement paste, i.e. the volumetric fractions of capillary pores, hydration products and unreacted cement, using high-resolution field emission scanning electron microscopy (FE-SEM) in the backscattered electron (BSE) mode and image analysis. From the obtained data and the volumetric increase of solids during cement hydration, we compute the initial free water content and cement content, hence the free w/c ratio. The same method can also be used to calculate the degree of hydration. The proposed method has the advantage that it is quantitative and does not require comparison with calibration graphs or reference samples made with the same materials and cured to the same degree of hydration as the tested sample. This paper reports the development, assumptions and limitations of the proposed method, and preliminary results from Portland cement pastes with a range of w/c ratios (0.25–0.50) and curing ages (3–90 days). We also discuss the extension of the technique to mortars and concretes, and samples made with blended cements. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S000888460900146X [article] Determining the water–cement ratio, cement content, water content and degree of hydration of hardened cement paste: Method development and validation on paste samples [texte imprimé] / H.S. Wong, Auteur ; N. R. Buenfeld, Auteur . - 2009 . - pp. 957–965. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 957–965 Mots-clés : Backscattered  electron  imaging  ;  Image  analysis  ;  Microstructure  ;  SEM  ;  w/c  ratio Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : We propose a new method to estimate the initial cement content, water content and free water/cement ratio (w/c) of hardened cement-based materials made with Portland cements that have unknown mixture proportions and degree of hydration. This method first quantifies the composition of the hardened cement paste, i.e. the volumetric fractions of capillary pores, hydration products and unreacted cement, using high-resolution field emission scanning electron microscopy (FE-SEM) in the backscattered electron (BSE) mode and image analysis. From the obtained data and the volumetric increase of solids during cement hydration, we compute the initial free water content and cement content, hence the free w/c ratio. The same method can also be used to calculate the degree of hydration. The proposed method has the advantage that it is quantitative and does not require comparison with calibration graphs or reference samples made with the same materials and cured to the same degree of hydration as the tested sample. This paper reports the development, assumptions and limitations of the proposed method, and preliminary results from Portland cement pastes with a range of w/c ratios (0.25–0.50) and curing ages (3–90 days). We also discuss the extension of the technique to mortars and concretes, and samples made with blended cements. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S000888460900146X