Name: concrete workability with the vebe test
Uploaded: 2024-11-07T14:48:28.000Z
Duration: 1 min 22 s
Channel: JoVE

L’essai Vebe est effectué sur du béton pour identifier sa maniabilité, de préférence pour les mélanges secs.
L’appareil d’essai comprend une chambre cylindrique mesurant neuf pouces et demi de diamètre et huit pouces de hauteur, un cône d’affaissement et un cavalier transparent en forme de disque. L’ensemble de cette installation est positionné sur une table vibrante.
Un cône d’affaissement standard placé dans le cylindre est rempli de béton de manière standard, et le cône d’affaissement est retiré, laissant le béton frais sous la forme d’un cône tronqué.
Ensuite, un cavalier transparent en forme de disque de 6 livres soutenu par l’appareil est placé sur le dessus du cône de béton.
Fonctionnant à 50 cycles par seconde, la table vibrante induit un mouvement vertical pour faciliter le compactage du béton dans le cylindre.
Le béton dans le cylindre est considéré comme complètement compacté lorsque le cavalier transparent est entièrement masqué, indiquant qu’il n’y a pas de vides visibles sur la surface du béton.
La maniabilité du mélange, indiquée par l’énergie nécessaire pour un compactage complet du béton, est mesurée en secondes Vebe, c’est-à-dire la durée de la transition du béton d’une forme de cône d’affaissement à un cylindre.

essai vébé

L’essai Vébé est une méthode utilisée pour mesurer l'ouvrabilité du béton, particulièrement efficace pour les mélanges de béton sec. Ce test utilise un appareil spécifique qui comprend une chambre cylindrique, un moule conique standard et une plaque transparente en forme de disque, le tout monté sur une table vibrante. La chambre cylindrique a des dimensions de 24 cm de diamètre et 20 cm de hauteur.


 Pour effectuer le test, le béton est déposé en couches dans le moule conique et compacté de manière standard. Une fois rempli, le moule conique est retiré, laissant le béton en forme de cône tronqué à l'intérieur du cylindre. Par la suite, une plaque transparente en forme de disque de 2,72 kg, soutenue par l'appareil, est placée sur le dessus du cône de béton.


 La table vibrante est ensuite activée à une fréquence de 50 Hertz pour induire des mouvements verticaux qui compactent le béton. La réalisation du compactage est déterminée lorsque la plaque transparente est complètement masquée par le béton, indiquant qu'il n'y a pas de vides visibles à la surface du béton.


 L'ouvrabilité du béton est quantifiée en termes de secondes Vébé, qui est le temps nécessaire au béton pour passer de la forme initiale de moule conique à une forme cylindrique entièrement compactée sous l'effet des vibrations. Cette durée reflète l'énergie nécessaire pour atteindre un compactage complet, fournissant une mesure de l'ouvrabilité du béton. Des secondes Vébé plus élevées indiquent une ouvrabilité plus faible, ce qui rend le béton plus rigide et plus difficile à compacter. Des secondes Vébé plus faibles suggèrent une ouvrabilité plus élevée, le béton étant plus fluide et plus facile à manipuler et à compacter.

Essai Vébé

L’essai Vebe est effectué sur du béton pour identifier sa maniabilité, de préférence pour les mélanges secs.
L’appareil d’essai comprend une chambre cylindrique de mesure ...

Education

Enseignement

JoVE Core

Civil Engineering

Génie civil

Unit 1

Unité 1

Fresh Concrete

Béton frais

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

Vebe Test

concrete workability with the vebe test

The Vebe test measures the workability of concrete, especially for dry mixes. Workability means how easy concrete is to handle and compact. The test uses a cylindrical chamber, a standard slump cone, and a transparent disc-shaped rider mounted on a vibrating table.

The cylindrical chamber measures nine and a half inches in diameter and eight inches in height. Concrete is placed into the slump cone in layers and compacted in the standard way. After the cone is removed, the concrete stays in the cylinder as a truncated cone.

A 6-pound transparent rider is then placed on top of the concrete cone. The vibrating table is turned on at 50 Hertz, which creates vertical movement and helps compact the concrete. The test is complete when the rider is fully hidden by the concrete, showing that no visible voids remain on the surface.

Workability is reported in Vebe seconds. This is the time it takes for the concrete to change from the slump cone shape to a fully compacted cylindrical shape under vibration. Higher Vebe seconds mean lower workability, so the concrete is stiffer and harder to compact. Lower Vebe seconds mean higher workability, so the concrete is more fluid and easier to handle and compact.

Concrete Workability with the Vebe Test

workability of concrete

Concrete Flow and Compaction Factors

Concrete workability is the ease with which fresh concrete can be mixed, placed, compacted, and finished. It is an important property during construction because it affects how well the material moves into position and how easily it can be shaped. Workability depends on the internal friction within the mix and the resistance it meets from molds and reinforcements. When the ingredients resist one another, concrete moves less easily. The same is true when it has to pass around barriers in the...

factors affecting workability

Concrete Workability and Mix Design Factors

Concrete workability depends on mix design factors that change how easily the material can be mixed, handled, and finished. The mix needs enough flow so it can move and be placed without losing quality. Water is a key part of this because it acts as a lubricant between the ingredients. The amount of water needed can change with the aggregates, or the solid particles in the mix. Finer particles and angular, rough-textured aggregates need more water than smooth, rounded ones because they have...

segregation in fresh concrete

How Concrete Mixes Separate During Placement

Fresh concrete can separate during placement, which changes how the mix is spread and can weaken the finished structure. This separation is called segregation. It happens when the parts of the mix no longer stay evenly blended. Segregation often occurs when concrete moves too much inside a form. It can also happen when the mix is dropped from a great height or pushed through narrow paths with sharp turns. In these cases, the heavier coarse aggregate settles at the bottom, while lighter...

bleeding in fresh concrete

Bleeding Water and Laitance in Fresh Concrete

Bleeding in fresh concrete happens when water from the mix rises to the surface after placement. The solid parts of the mix do not hold all the water as they settle, so separation occurs and water collects on top. Engineers can measure the severity of bleeding by checking total settlement or by noting how much the concrete height drops per unit height. Bleeding can create weak spots inside the concrete. Rising water may get trapped under large aggregate particles or reinforcement bars, which...

slump test

Concrete Workability Check with Slump

The slump test checks the workability of fresh concrete. Workability means how easy the mix is to place and handle. The test uses a 12-inch-high truncated cone mold that narrows from eight inches at the base to four inches at the top. Before testing, the mold is fixed to a flat base and dampened. Concrete is added in three layers. Each layer is compacted 25 times with a steel tamping rod that is five-eighths of an inch in diameter and has a rounded end. This helps spread the concrete evenly...

compacting factor test

Concrete Workability by Compacting Factor

The compacting factor test measures the workability of concrete. Workability describes how easily concrete can move and fill a mold or form during construction. This test is especially suitable for concrete mixes with aggregates up to one and a half inches in size. The setup uses specialized equipment with two truncated cone-shaped hoppers and a cylinder. All of the inside surfaces are polished to reduce friction. Concrete is first placed into the upper hopper without any compaction. Then the...

vebe test

The Vebe test measures the workability of concrete, especially for dry mixes. Workability means how easy concrete is to handle and compact. The test uses a cylindrical chamber, a standard slump cone, and a transparent disc-shaped rider mounted on a vibrating table. The cylindrical chamber measures nine and a half inches in diameter and eight inches in height. Concrete is placed into the slump cone in layers and compacted in the standard way. After the cone is removed, the concrete stays in the...

flow table test

Concrete Spread Measured by Flow Table

The flow table test measures how far fresh concrete spreads, which helps assess workability. Workability means how easily concrete can flow and settle under its own weight. The method is useful for highly flowable concrete mixes. The test uses a flow table made from a wooden board with a steel plate on top. Together, the parts weigh 35 pounds. The board is hinged to a base and measures 27.6 inches on each side. A truncated cone mold is also used. It is 8 inches high, with an 8-inch base...

key terms and concepts

Learn how the Vebe test measures concrete workability for dry mixes using vibration, a slump cone, and Vebe seconds to show compaction time.

Concrete Workability with the Vebe Test | JoVE K12

JoVE Core Civil Engineering provides a foundational exploration of essential construction materials in civil engineering, focusing on bricks, stones, steel, wood, and concrete through easy-to-understand animated videos. This collection covers the properties, manufacturing processes, and practical applications of these materials. Additionally, the accompanied science-in-action videos demonstrate the research experiments performed in laboratories.

civil engineering

Concrete Workability with the Vebe Test

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