Name: concrete workability check with slump
Uploaded: 2024-11-07T14:48:28.000Z
Duration: 1 min 20 s
Channel: JoVE

O teste de abatimento mede a trabalhabilidade do concreto e usa um molde de cone truncado de 12 polegadas de altura, estreitando de oito polegadas na base para quatro polegadas na parte superior, firmemente preso a uma base plana antes que o concreto seja preenchido.
O concreto é adicionado ao molde umedecido em três camadas, cada uma compactada 25 vezes usando uma haste de compactação de aço com um diâmetro de cinco oitavos de polegada e extremidade arredondada. Finalmente, a superfície superior é riscada.
Após o enchimento, o cone é levantado suavemente e o concreto cai. Essa diminuição em sua altura, chamada de queda, é medida até o quarto de polegada mais próximo.
Uma queda uniforme é chamada de queda verdadeira, enquanto o concreto que desliza pelo molde indica uma queda de cisalhamento, que requer novos testes. A queda persistente do cisalhamento sugere que a mistura carece de coesão.
Às vezes, o concreto pode entrar em colapso para misturas magras, o que destaca a falta de confiabilidade do teste de abatimento para misturas magras.
A queda, muito alta ou muito baixa, serve como um alerta imediato, levando à correção do problema com a mistura na concretagem a granel. Os valores de abatimento recomendados para diferentes habilidades de trabalho são predeterminados.

teste de abatimento

O teste de abatimento é um método amplamente utilizado para medir a trabalhabilidade do concreto. Ele emprega um molde de cone truncado de 30,48 centímetros de altura que afunila de 20,32 centímetros na base para 10,16 centímetros no topo. Antes do teste, o molde é firmemente preso a uma base plana e umedecido.

O concreto é despejado no molde em três camadas para conduzir o teste. Cada camada é compactada 25 vezes com uma haste de compactação de aço, que tem um diâmetro de 1,58 centímetros e uma extremidade arredondada, para garantir uma distribuição uniforme e eliminar bolsas de ar. Após a compactação, a superfície superior do concreto é nivelada.

Uma vez que o molde é preenchido, ele é suavemente levantado para cima, permitindo que o concreto afunde devido à gravidade. A diminuição na altura do concreto, conhecida como abatimento, é então medida com precisão de 0,63 centímetros. Um abatimento adequado, onde o concreto mantém sua forma cônica, é um abatimento verdadeiro. Se o concreto colapsar ou se espalhar, indicando um abatimento por cisalhamento, o teste pode precisar ser repetido, pois sugere que a mistura não tem coesão e pode ser problemático para aplicações estruturais.

Valores de abatimento excessivamente altos ou baixos são indicadores de problemas potenciais na mistura de concreto, exigindo ajustes. O teste de abatimento é particularmente eficaz para identificar a necessidade imediata de correções em operações de concretagem a granel, embora possa ser menos confiável para misturas magras, onde o concreto tende a colapsar. Os valores de abatimento recomendados são predeterminados com base nos requisitos específicos para diferentes tipos de trabalhabilidade.

Teste de abatimento

O teste de abatimento mede a trabalhabilidade do concreto e usa um molde de cone truncado de 12 polegadas de altura, estreitando de oito polegadas na base para quatro polegadas na ...

Education

JoVE Core

Civil Engineering

Engenharia Civil

Unit 1

Unidade 1

Fresh Concrete

Concreto Fresco

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

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 and remove air pockets. The top surface is then leveled off.

After the mold is full, it is lifted straight up. The concrete drops under gravity, and the drop in height is called the slump. The slump is measured to the nearest quarter inch. If the concrete keeps its cone shape, it is called a true slump.

If the concrete collapses or spreads out, it is a shear slump. That result can mean the mix lacks cohesion and may not work well for structural use. Very high or very low slump values also point to problems in the mix and may require adjustment. The slump test is especially useful for finding quick fixes in bulk concreting work, but it may be less reliable for lean mixes that tend to collapse. Recommended slump values are set ahead of time for the workability needed in each type of job.

Concrete Workability Check with Slump

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

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

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

Learn how the slump test measures concrete workability using a cone mold, layered filling, tamping, and slump measurement for fresh concrete.

Concrete Workability Check with Slump | 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 Check with Slump

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