Name: concrete workability by compacting factor
Uploaded: 2024-11-07T14:48:28.000Z
Duration: 1 min 22 s
Channel: JoVE

L’essai du facteur de compactage détermine la maniabilité du béton avec des granulats allant jusqu’à un pouce et demi maximum.
L’équipement d’essai se compose de deux trémies tronquées en forme de cône avec des portes à charnières au bas et d’un cylindre, le tout empilé séquentiellement, avec des surfaces intérieures polies pour réduire la friction.
Le béton est placé dans la trémie supérieure sans compactage, et la porte inférieure est ouverte, laissant le béton s’écouler dans la trémie inférieure.
Ensuite, la porte inférieure de la trémie inférieure est ouverte, ce qui permet au béton de tomber dans le cylindre situé en dessous, et l’excès de béton est frappé.
Une tige d’acier est utilisée pour piquer et déloger doucement le béton qui se coince dans l’une ou les deux trémies pendant l’essai.
Le poids final du béton dans le volume de prise du cylindre est déterminé et la masse volumique de ce béton partiellement compacté est calculée.
La densité entièrement compactée est déterminée en remplissant le cylindre de béton en quatre couches et en tapotant chaque couche.
Enfin, le facteur de compactage est calculé comme le rapport entre la masse volumique du béton partiellement compacté et la masse volumique du béton entièrement compacté, ce qui indique la maniabilité du mélange.

test du facteur de compactage

L'essai de facteur de compactage est une méthode utilisée pour évaluer l’ouvrabilité du béton. Il est particulièrement adapté aux mélanges de béton contenant des agrégats d'une taille allant jusqu'à 3,81 centimètres. Cet essai nécessite un équipement spécialisé composé de deux trémies en forme de cône tronqué et d'un cylindre, tous dotés de surfaces intérieures polies pour minimiser la friction.


 La procédure commence par la mise en place du béton dans la trémie supérieure sans compactage. Une fois remplie, la porte inférieure de cette trémie est ouverte, permettant au béton de s'écouler dans la trémie inférieure. Une fois la trémie inférieure remplie, sa porte inférieure est alors ouverte pour laisser tomber le béton dans le cylindre placé en dessous. Le béton en excès est ensuite éliminé pour niveler la surface.


 Pendant l'essai, une tige en acier peut être utilisée pour percer doucement et déloger tout béton qui pourrait rester coincé dans les trémies. Le poids du béton dans le cylindre est enregistré et sa densité lorsqu'il est partiellement compacté est calculée. À titre de comparaison, la densité du béton entièrement compacté est déterminée en remplissant le même cylindre de béton en quatre couches et en tassant soigneusement chaque couche pour assurer un compactage maximal.


 Le facteur de compactage est calculé comme le rapport entre la densité du béton partiellement compacté et la densité du béton entièrement compacté. Ce rapport fournit une valeur numérique qui indique l’ouvrabilité du béton, les différents niveaux du facteur de compactage reflétant différents degrés d’ouvrabilité. Ce test est essentiel pour comprendre comment le béton se comportera lorsqu'il sera placé dans des moules ou des coffrages lors de projets de construction.

Test du facteur de compactage

L’essai du facteur de compactage détermine la maniabilité du béton avec des granulats allant jusqu’à un pouce et demi maximum.
L’équipement de test ...

Education

Enseignement

JoVE Core

Civil Engineering

Génie civil

Unit 1

Unité 1

Fresh Concrete

Béton frais

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

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 bottom door is opened so the mix can flow into the lower hopper.

After the lower hopper fills, its bottom door is opened. The concrete falls into the cylinder below. Extra concrete is struck off to make the surface level. If concrete gets stuck in the hoppers, a steel rod may be used to gently poke it loose.

Next, the weight of the concrete in the cylinder is recorded. This gives the density of the partially compacted concrete. For comparison, the same cylinder is filled with concrete in four layers and each layer is tamped thoroughly to reach maximum compaction. The compacting factor is then calculated as the ratio of the partially compacted density to the fully compacted density. This number shows the workability of the concrete and helps predict how the mix will behave in forms.

Concrete Workability by Compacting Factor

concrete-workability-by-compacting-factor

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

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

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...

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

Measure concrete workability with the compacting factor test using hoppers and a cylinder. Learn how partially and fully compacted densities are compared.

Concrete Workability by Compacting Factor | 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 by Compacting Factor

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