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

O ensaio de Vebe é realizado em concreto para identificar sua trabalhabilidade, preferencialmente para misturas secas.
O aparelho de teste compreende uma câmara cilíndrica medindo nove polegadas e meia de diâmetro e oito polegadas de altura, um cone de queda e um cavaleiro transparente em forma de disco. Toda essa configuração é posicionada em uma mesa vibratória.
Um cone de abatimento padrão colocado no cilindro é preenchido com concreto de maneira padrão, e o cone de abatimento é removido, deixando o concreto fresco na forma de um cone truncado.
Em seguida, um piloto transparente em forma de disco de 6 libras suportado pelo aparelho é colocado no topo do cone de concreto.
Operando a 50 ciclos por segundo, a mesa vibratória induz um movimento vertical para facilitar a compactação do concreto no cilindro.
O concreto no cilindro é considerado completamente compactado quando o condutor transparente está totalmente obscurecido, indicando que não há vazios visíveis na superfície do concreto.
A trabalhabilidade da mistura, indicada pela energia necessária para a compactação total do concreto, é medida em segundos Vebe, que é a duração da transição do concreto de uma forma de cone de abatimento para um cilindro.

teste vebe

O teste Vebe é um método usado para medir a trabalhabilidade do concreto, particularmente eficaz para misturas de concreto seco. Este teste emprega um aparelho específico que inclui uma câmara cilíndrica, um cone de abatimento padrão e um piloto transparente em forma de disco, todos montados em uma mesa vibratória. A câmara cilíndrica tem dimensões de 24,13 centímetros de diâmetro e 20,32 centímetros de altura e é colocada dentro da câmara cilíndrica.

Para conduzir o teste, o concreto é colocado no cone de abatimento. O concreto é preenchido em camadas e compactado de forma padrão. Uma vez preenchido, o cone de abatimento é removido, deixando o concreto na forma de um cone truncado dentro do cilindro. Posteriormente, um piloto transparente em forma de disco de 2,72 quilos, apoiado pelo aparelho, é colocado em cima do cone de concreto.

A mesa vibratória é então ativada a uma frequência de 50 Hertz para induzir movimentos verticais que compactam o concreto. A conclusão da compactação é determinada quando o condutor transparente fica totalmente obscurecido pelo concreto, indicando que não há vazios visíveis na superfície do concreto.

A trabalhabilidade do concreto é quantificada em termos de segundos de Vebe, que é o tempo que leva para o concreto fazer a transição do formato de cone de abatimento inicial para um formato cilíndrico totalmente compactado sob vibração. Essa duração reflete a energia necessária para atingir a compactação total, fornecendo uma medida da trabalhabilidade do concreto. Segundos de Vebe mais altos indicam menor trabalhabilidade, tornando o concreto mais rígido e mais difícil de compactar. Segundos de Vebe mais baixos sugerem maior trabalhabilidade, com o concreto sendo mais fluido e mais fácil de manusear e compactar.

Teste Vebe

O ensaio de Vebe é realizado em concreto para identificar sua trabalhabilidade, preferencialmente para misturas secas.
O aparelho de teste compreende uma câmara cilíndrica que mede ...

Education

JoVE Core

Civil Engineering

Engenharia Civil

Unit 1

Unidade 1

Fresh Concrete

Concreto Fresco

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

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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