A unique experimental method for monitoring aggregate settlement in concrete

Petrou, Michael F.; Harries, Kent A.; Gadala-Maria, Francis; Kolli, Venkata Giri

doi:10.1016/s0008-8846(00)00223-4

Cited by 60 publications

(26 citation statements)

References 6 publications

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“…12,22 The origin of the yield stress may be contributed by three primary sources. 23 One source is the mechanical interlocking between aggregates that give rise to internal friction. 24 The second source may be attributed to the attractive forces between the cement and other submicron particles 25 .…”

Section: Discussionmentioning

confidence: 99%

Workability of air-entrained lightweight concrete from rheology perspective

Chia

Zhang

2007

Magazine of Concrete Research

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Effects of air entrainment on rheological parameters and slump of fresh lightweight aggregate concrete were studied. Results show that yield stress and plastic viscosity of air-entrained concrete were lower than those of nonair-entrained concrete with similar superplasticiser dosage. As the entrained-air content increased, the plastic viscosity decreased whereas the yield stress remained relatively unchanged. The slump of the air-entrained concrete was significantly higher than the non-air-entrained concrete. At similar yield stress, the slump of the air-entrained concrete was higher owing to its lower plastic viscosity by air entrainment. At similar slump, the air-entrained concrete had higher yield stress and lower plastic viscosity, implying that higher shear stress is needed to initiate flow but flow resistance would be lower.

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Section: Discussionmentioning

confidence: 99%

Workability of air-entrained lightweight concrete from rheology perspective

Chia

Zhang

2007

Magazine of Concrete Research

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“…Dentro del primer grupo hay muchos tipos (6,10,11,12,13), algunos de los cuales se basan en establecer la resistencia a la segregación en función de las propiedades reológicas del material. No obstante, los resultados que se obtienen con estos últimos son algo contradictorios, alcanzándose buenas correlaciones en unos casos (14) y malas en otros (7,15,16).…”

Section: Introductionunclassified

“…The first group comprises many different types of procedures (6,10,11,12,13), some of which establish the resistance to segregation on the basis of concrete rheology. These tests may yield contradictory results, however, with good correlations in some cases (14) and poor in others (7,15,16).…”

Section: Introductionmentioning

confidence: 99%

Homogeneidad de los hormigones autocompactantes

2007

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RESUMENEn este trabajo se estudia la homogeneidad de los hormigones autocompactantes en piezas hormigonadas verticalmente, determinando su resistencia a la segregación y la uniformidad de su estructura porosa, dado que la pér-dida de estabilidad de una mezcla puede conducir a una distribución no uniforme de sus propiedades. Para ello se han fabricado dos tipos de hormigones, uno autocompactante y otro tradicional vibrado, con diferentes relaciones a/c y distintos tipos de cemento. Los resultados ponen de manifiesto que los hormigones autocompactantes presentan una buena resistencia a la segregación, aunque algo menor que la registrada en los hormigones tradicionales. A pesar de ello, su estructura porosa tiende a ser ligeramente más uniforme, debido probablemente a un menor sangrado. Asimismo, presentan una mayor densidad aparente, una menor porosidad y un menor tamaño medio de poro, lo que les confiere mejores prestaciones frente a la penetración de agua bajo presión. Ahora bien, para diá-metros de poro superiores aproximadamente a 0,5 µm, la distribución de tamaños de poro es similar a la de los hormigones tradicionales, dando lugar a una absorción también similar.Palabras clave: hormigón autocompactante, segregación, porosidad, absorción, permeabilidad. SUMMARYConcrete instability may lead to the non-uniform distribution of its properties. The homogeneity of self-consolidating concrete in vertically cast members was therefore explored in this study, analyzing both resistance to segregation and pore structure uniformity. To this end, two series of concretes were prepared, self-consolidating and traditional vibrated materials, with different w/c ratios and types of cement. The results showed that selfconsolidating concretes exhibit high resistance to segregation, albeit slightly lower than found in the traditional mixtures. The pore structure in the former, however, tended to be slightly more uniform, probably as a result of less intense bleeding. Such concretes are also characterized by greater bulk density, lower porosity and smaller mean pore size, which translates into a higher resistance to pressurized water. For pore diameters of over about 0.5 µm, however, the pore size distribution was found to be similar to the distribution in traditional concretes, with similar absorption rates. Key yw wor rds: self-consolidating concrete, segregation, porosity, absorption, permeability. Persona de contacto/Corresponding author: mvalcuen@csa.upv.es INTRODUCCIÓNEl hormigón autocompactante (HAC) puede definirse como aquel que es capaz de fluir en el interior del encofrado, pasando entre las armaduras y consolidándose úni-camente bajo la acción de su propio peso, sin necesidad de compactación y sin presentar segregación o exudación.Una de las dificultades que plantea la fabricación de este tipo de hormigones es la estabilidad de la mezcla, pues a medida que aumenta la fluidez del material, su resistencia a la segregación disminuye, y puede dar lugar durante el vertido a bloqueos de los áridos al pasar por zonas congestio...

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“…The commonly used methods include flow measurement (Zain 1999), water content measurement (Nagi and Whiting 1994), water-to-cement ratio (w/c) determination (Naik and Ramme 1989) (Petrou et al 2000). These existing test methods can neither describe mixing efficiency nor monitor concrete uniformity.…”

Section: Introductionmentioning

confidence: 99%

Use of a Moisture Sensor for Monitoring the Effect of Mixing Procedure on Uniformity of Concrete Mixtures

Wang

2005

ACT

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The present research is to explore a new approach to monitoring uniformity of concrete mixtures. A given concrete mix was subjected to three different mixing procedures. A moisture sensor was installed inside a pan mixer to monitor moisture content of the concrete mixtures during mixing. The concrete mixtures were considered as uniformly mixed when stable moisture content was detected by the moisture sensor. The concrete workability and strength were then evaluated, and the concrete's microstructure (pore distributions and aggregate-paste interface) was examined. The preliminary results indicated that the moisture sensor provided reliable test results describing moisture distribution in concrete mixtures. The sensor readings well captured the subtle changes, such as the loading sequence of concrete materials, in the concrete mixing process. The material loading sequence, mixing time, and aggregate moisture condition had significant influences on the concrete workability, air void system, and strength. These research results provide researchers and engineers with insight into the control of concrete mixing quality and the optimization of mixing procedures in the lab and field.

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A unique experimental method for monitoring aggregate settlement in concrete

Cited by 60 publications

References 6 publications

Workability of air-entrained lightweight concrete from rheology perspective

Workability of air-entrained lightweight concrete from rheology perspective

Homogeneidad de los hormigones autocompactantes

Use of a Moisture Sensor for Monitoring the Effect of Mixing Procedure on Uniformity of Concrete Mixtures

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