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

La prueba de asentamiento mide la trabajabilidad del concreto y utiliza un molde de cono truncado de 12 pulgadas de alto, que se estrecha de ocho pulgadas en la base a cuatro pulgadas en la parte superior, unido de forma segura a una base plana antes de que se llene el concreto.
El concreto se agrega al molde humedecido en tres capas, cada una compactada 25 veces con una varilla apisonadora de acero con un diámetro de cinco octavos de pulgada y un extremo redondeado. Finalmente, se golpea la superficie superior.
Después del llenado, el cono se levanta suavemente y el hormigón se desploma. Esta disminución en su altura, llamada hundimiento, se mide hasta el cuarto de pulgada más cercano.
Un asentamiento uniforme se denomina asentamiento verdadero, mientras que el concreto que se desliza por el molde indica un asentamiento por cizallamiento, que requiere volver a realizar la prueba. El hundimiento persistente del cizallamiento sugiere que la mezcla carece de cohesión.
A veces, el concreto puede colapsar para mezclas magras, lo que destaca la falta de confiabilidad de la prueba de asentamiento para mezclas magras.
El desplome, ya sea demasiado alto o demasiado bajo, sirve como una alerta inmediata, lo que provoca la corrección del problema con el hormigonado de la mezcla a granel. Los valores de asentamiento recomendados para diferentes capacidades de trabajo están predeterminados.

prueba de caída

La prueba de asentamiento es un método ampliamente utilizado para medir la trabajabilidad del hormigón. Se utiliza un molde de cono truncado de 30,48 centímetros de alto que se estrecha desde 20,32 centímetros en la base hasta 10,16 centímetros en la parte superior. Antes de la prueba, el molde se fija firmemente a una base plana y se humedece.

Para realizar la prueba, se vierte el hormigón en el molde en tres capas. Cada capa se compacta 25 veces con una varilla de acero, que tiene un diámetro de 1,58 centímetros y un extremo redondeado, para garantizar una distribución uniforme y eliminar las bolsas de aire. Después de la compactación, se nivela la superficie superior del hormigón.

Una vez que el molde está lleno, se levanta suavemente hacia arriba, permitiendo que el hormigón se hunda hacia abajo debido a la gravedad. Luego, se mide la disminución de la altura del hormigón, denominada hundimiento, con una precisión de 0,63 centímetros. Un hundimiento adecuado, en el que el hormigón mantiene su forma cónica, es un hundimiento verdadero. Si el hormigón colapsa o se extiende, lo que indica un hundimiento por corte, es posible que sea necesario repetir la prueba, ya que sugiere que la mezcla carece de cohesión y podría ser problemática para aplicaciones estructurales.

Los valores de asentamiento excesivamente altos o bajos son indicadores de posibles problemas en la mezcla de hormigón, que requieren ajustes. La prueba de asentamiento es particularmente eficaz para identificar la necesidad inmediata de realizar correcciones en operaciones de hormigonado en masa, aunque puede ser menos fiable para mezclas pobres en las que el hormigón tiende a desplomarse. Los valores de asentamiento recomendados están predeterminados en función de los requisitos específicos para los diferentes tipos de trabajabilidad.

Prueba de caída

La prueba de asentamiento mide la trabajabilidad del concreto y utiliza un molde de cono truncado de 12 pulgadas de alto, que se estrecha de ocho pulgadas en la base a cuatro pulgadas en la ...

Education

Educación

JoVE Core

Civil Engineering

Ingeniería Civil

Unit 1

Unidad 1

Fresh Concrete

Hormigón fresco

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

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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