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A platform for research: civil engineering, architecture and urbanism
Frost resistance, chloride transport and related microstructure of field self-compacting concrete
The Swedish development of Self-Compacting Concrete (SCC) started in 1993 and since then the interest and use of SCC has been growing steadily. This contribution summarises results from different projects, financed by road authorities, contractors and development funds. Measurements and laboratory analyses of drilled samples from field objectives were carried out at the Swedish Cement and Concrete Research Institute (CBI). The study focuses on frost resistance, chloride transport and related microstructure in SCC from tunnel linings, bridges and retaining walls. The results showed that the resistance against freeze-thaw action with 3 % NaCl solution was very good for SCC with W/C-ratios of about 0.50. Parameters characterising the air-void structure was measured by image analysis. Surprisingly, and in contradiction with previously reported results from investigations with conventional concretes (CC), specimens with high power's spacing factors and low specific surface areas showed good freeze-thaw performance. Total air content rather than power spacing factor influenced the frost resistance. This suggests that other factors than the air-void structure influence the freeze-thaw susceptibility of SCC. Examples of such factors are the density of the interfacial transition zone (ITZ), the homogeneity and density of the bulk paste, micro bleeding in the fresh state and the conductivity of the capillary pore system (W/C-ratio ). After thin section studies of the microstructure in freeze-thaw tested SCC it was concluded that porosity of the ITZ and the occurrence of voids due to micro bleeding were decisive for the frost resistance of the investigated SCC. Measurements of the rate of chloride transport were obtained by chloride analyses and calculations of the chloride diffusion coefficient (DCl(-)). The study on chloride transport showed that SCC has a higher resistance against chloride penetration than CC at equivalent W/C-ratios. The good freeze-thaw performance and chloride diffusivity of SCC can be due to the increased dispersion of cement and filler, improved stability of the particle slurry and a dense ITZ. The results indicate that well mix-designed and robust SCC is more durable than vibrated CC at equivalent W/C-ratios.
Frost resistance, chloride transport and related microstructure of field self-compacting concrete
The Swedish development of Self-Compacting Concrete (SCC) started in 1993 and since then the interest and use of SCC has been growing steadily. This contribution summarises results from different projects, financed by road authorities, contractors and development funds. Measurements and laboratory analyses of drilled samples from field objectives were carried out at the Swedish Cement and Concrete Research Institute (CBI). The study focuses on frost resistance, chloride transport and related microstructure in SCC from tunnel linings, bridges and retaining walls. The results showed that the resistance against freeze-thaw action with 3 % NaCl solution was very good for SCC with W/C-ratios of about 0.50. Parameters characterising the air-void structure was measured by image analysis. Surprisingly, and in contradiction with previously reported results from investigations with conventional concretes (CC), specimens with high power's spacing factors and low specific surface areas showed good freeze-thaw performance. Total air content rather than power spacing factor influenced the frost resistance. This suggests that other factors than the air-void structure influence the freeze-thaw susceptibility of SCC. Examples of such factors are the density of the interfacial transition zone (ITZ), the homogeneity and density of the bulk paste, micro bleeding in the fresh state and the conductivity of the capillary pore system (W/C-ratio ). After thin section studies of the microstructure in freeze-thaw tested SCC it was concluded that porosity of the ITZ and the occurrence of voids due to micro bleeding were decisive for the frost resistance of the investigated SCC. Measurements of the rate of chloride transport were obtained by chloride analyses and calculations of the chloride diffusion coefficient (DCl(-)). The study on chloride transport showed that SCC has a higher resistance against chloride penetration than CC at equivalent W/C-ratios. The good freeze-thaw performance and chloride diffusivity of SCC can be due to the increased dispersion of cement and filler, improved stability of the particle slurry and a dense ITZ. The results indicate that well mix-designed and robust SCC is more durable than vibrated CC at equivalent W/C-ratios.
Frost resistance, chloride transport and related microstructure of field self-compacting concrete
Frostbeständigkeit und Chloridtransport in Zusammenhang mit dem Mikrogefüge in Feldproben von selbstverdichtendem Beton
Trägardh, J. (author) / Skoglund, P. (author) / Westerholm, M. (author)
2003
11 Seiten, 12 Bilder, 3 Tabellen, 11 Quellen
Conference paper
English
Baustoff , Bildanalyse , Chlorid , Chloridkorrosion , Dichte (Masse) , Diffusion , Diffusionskoeffizient , Frostbeständigkeit , Frostrissigkeit , Frost-Tauwechsel-Prüfung , Gasgehalt , Hohlraum , Kapillaritätsmessung , Korrosionsbeständigkeit , Mikrogefüge , Natriumchlorid , Porengrößenverteilung , selbstverdichtender Beton , spezifische Oberfläche , Vergleichsuntersuchung , Wasser-Zement-Wert , Mikroentmischung , Luftgehalt
FROST RESISTANCE, CHLORIDE TRANSPORT AND RELATED MICROSTRUCTURE OF FIELD SELF-COMPACTING CONCRETE
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