Name: concrete spread measured by flow table
Uploaded: 2024-11-07T14:48:28.000Z
Duration: 1 min 12 s
Channel: JoVE

Der Fließtabellentest, der verwendet wird, um die Verarbeitbarkeit von Beton zu ermitteln und hochfließfähigen Beton zu bewerten, umfasst eine Vorrichtung, die aus einem Holzbrett besteht, das mit einer Stahlplatte überzogen ist, mit einem Gesamtgewicht von 35 Pfund.
Ein Scharnier verbindet die Platine mit einer Basis, wobei jede Seite der Platine 27,6 Zoll misst.
Das obere Brett ist so konzipiert, dass es auf eine Höhe von 1,6 Zoll angehoben werden kann, und der Tisch verfügt über spezielle Markierungen, die zeigen, wo der Beton platziert werden sollte.
Ein 8 Zoll hoher Kegelstumpf mit einem Basisdurchmesser von 8 Zoll und einem oberen Durchmesser von 5 Zoll wird mit Beton gefüllt. Er wird schonend verdichtet, überschüssiger Beton wird weggeräumt und die Kegelform wird nach 30 Sekunden vorsichtig entfernt.
Der Tisch wird 15 Mal ruckartig geschüttelt, wobei jeder Ruck im Abstand von 4 Sekunden erfolgt, wodurch sich der Beton ausbreitet.
Der Durchschnitt der Ausdehnung der Streuung parallel zu den beiden Kanten des Tisches, gemessen nach dem Rütteln, gibt die Verarbeitbarkeit des Betons an, wobei spezifische Werte der mittleren oder hohen Verarbeitbarkeit entsprechen.

ausbreitversuch

Der Ausbreitversuch ist eine bewährte Methode zur Beurteilung der Verarbeitbarkeit von Beton und eignet sich besonders zur Bewertung von Betonmischungen mit hoher Fließfähigkeit. Bei diesem Test wird ein Gerät verwendet, das aus einem Holzbrett mit einer darauf liegenden Stahlplatte besteht und insgesamt etwa 15,87 Kilogramm wiegt. Das Brett ist über ein Scharnier mit einer Basis verbunden und misst auf jeder Seite 70,10 Zentimeter.


 Beton wird in eine kegelstumpfförmige Form mit einer Höhe von 20,32 cm, einem Basisdurchmesser von 20,32 cm und einem oberen Durchmesser von 12,70 cm gegeben. Der Beton wird vorsichtig verdichtet, überschüssiger Beton wird entfernt und die Form wird nach 30 Sekunden entfernt.


 Beim Testverfahren wird der Tisch 15 Mal im Abstand von 4 Sekunden gerüttelt, indem die obere Platte auf eine Höhe von 4,06 cm angehoben wird. Dadurch breitet sich der Beton aus seiner ursprünglichen kegelförmigen Form aus. Nach dem Rütteln wird das Ausmaß der Ausbreitung des Betons parallel zu den beiden Tischkanten gemessen. Die durchschnittliche Ausbreitung wird berechnet, um die Verarbeitbarkeit des Betons zu beurteilen. Anhand bestimmter Ausbreitungswerte wird die Verarbeitbarkeit des Betons als mittel oder hoch eingeteilt. Dieser Test liefert wichtige Daten zur Fähigkeit des Betons, unter seinem Eigengewicht zu fließen und sich abzusetzen, und spiegelt damit seine Eignung für verschiedene Bauanwendungen wider, bei denen eine hohe Fließfähigkeit und gleichmäßige Verteilung erforderlich sind.

Ausbreitversuch

Der Fließtabellentest, der zur Ermittlung der Verarbeitbarkeit von Beton und zur Bewertung von stark fließfähigem Beton verwendet wird, umfasst eine Vorrichtung, die aus einer Holzplatte besteht ...

Education

Lehre

JoVE Core

Civil Engineering

Bauingenieurwesen

Unit 1

Einheit 1

Fresh Concrete

Frischer Beton

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

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 diameter and a 5-inch top diameter.

The concrete is placed in the mold and gently compacted. Then the excess is cleared away. After 30 seconds, the mold is removed. The table is jolted 15 times at 4-second intervals by lifting the upper board to a height of 1.6 inches. This motion makes the concrete spread out from its cone shape.

After jolting, the spread is measured parallel to the two edges of the table. The average spread is then calculated. This value is used to judge the concrete's workability. The results can place the mix in medium or high workability categories. The test gives useful data for construction applications that need high fluidity and even distribution.

Concrete Spread Measured by Flow Table

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

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

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 flow table test. Learn the mold size, jolting steps, and how spread is used to classify flowable mixes.

Concrete Spread Measured by Flow Table | 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 Spread Measured by Flow Table

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