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

スランプ試験はコンクリートの施工性を測定し、コンクリートが充填される前に平らなベースにしっかりと取り付けられた、ベースで8インチから上部で4インチに狭くなる高さ12インチの切り捨てコーン型を使用します。
コンクリートは、減衰した型枠に3層で追加され、それぞれが直径8分の5インチの丸みを帯びた端を持つ鋼製のタンピングロッドを使用して25回圧縮されます。最後に、上面を打ちます。
充填後、コーンはゆっくりと持ち上げられ、コンクリートはスランプします。この高さの減少はスランプと呼ばれ、最も近い1/4インチまで測定されます。
均一なスランプは真のスランプと呼ばれ、型枠を滑り落ちるコンクリートはせん断スランプを示し、再テストが必要です。持続的なせん断スランプは、ミックスがまとまりを欠いていることを示唆しています。
リーンミックスではコンクリートが崩壊することがあり、リーンミックスに対するスランプテストの信頼性の低さが浮き彫りになります。
スランプが高すぎるか低すぎるかは、即時のアラートとして機能し、バルクコンクリートの混合物の問題の修正を促します。さまざまな作業性に対する推奨スランプ値は事前に決定されています。

スランプ試験

スランプ試験は、コンクリートの作業性を測定するために広く使用されている方法です。この試験では、底部 20.32 cm から上部 10.16 cm まで細くなる、高さ 30.48 cm の円錐台型を使用します。試験の前に、型は平らな基礎にしっかりと固定され、湿らせます。


 試験を行うために、コンクリートは 3 層に分けられ、型枠に流し込まれます。各層は、均一な分布を確保し、空気ポケットを排除するために、直径 5/8 インチ（約1.6センチメートル）で先端が丸い鋼製の突き棒で 25 回圧縮されます。圧縮後、コンクリートの上部表面を平らにします。


 型枠にコンクリートを充填したら、ゆっくりと持ち上げて、重力によりコンクリートが下方に沈むようにします。コンクリートの高さの減少はスランプと呼ばれ、0.63 cm 単位で測定されます。コンクリートが円錐形を維持する適切なスランプが真のスランプ (True slump) です。コンクリートが崩壊したり広がったりしてせん断スランプ (Shear slump) を示している場合は、混合物に凝集力が欠けていることを示し、構造用途に問題が生じる可能性があるため、試験を繰り返す必要がある場合があります。


 スランプ値が高すぎたり低すぎたりすると、コンクリート混合物に潜在的な問題があることを示し、調整が必要です。スランプ試験は、バルクコンクリート作業で修正がすぐに必要かどうかを特定するのに特に効果的ですが、コンクリートが崩壊する傾向がある貧配合では信頼性が低い場合があります。推奨されるスランプ値は、さまざまな作業性に対する特定の要件に基づいて事前に決定されます。

スランプ試験では、コンクリートの施工性を測定し、高さ12インチの切り捨てコーン型を使用し、基部の8インチから4インチに絞り込みます...

Education

JoVE Core

Civil Engineering

土木工学

Unit 1

ユニット1

Fresh Concrete

生コンクリート

KEY TERMS AND CONCEPTS

主要用語および概念

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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