Name: concrete workability by compacting factor
Uploaded: 2024-11-07T14:48:28.000Z
Duration: 1 min 22 s
Channel: JoVE

締固め係数試験は、骨材サイズが最大1.5インチまでのコンクリートの施工性を決定します。
試験装置は、底部にヒンジ付きドアを備えた2つの円錐形ホッパーとシリンダーで構成されており、すべて順番に積み重ねられ、内部表面は摩擦を減らすために研磨されています。
コンクリートは圧縮されずに上部ホッパーに配置され、下部のドアが開かれ、コンクリートが下部ホッパーに流れ込みます。
次に、下部ホッパーの下部ドアが開き、コンクリートが下のシリンダーに落ち、余分なコンクリートが打ち落とされます。
スチールロッドを使用して、テスト中に一方または両方のホッパーに詰まったコンクリートを優しく突き刺して取り除きます。
シリンダーの設定体積内のコンクリートの最終的な重量が決定され、この部分的に圧縮された密度が計算されます。
完全に圧縮された密度は、シリンダーを4つの層にコンクリートで満たし、各層を突き固めることによって決定されます。
最後に、締固め係数は、部分的に締固められたコンクリートの密度と完全に締固められたコンクリートの密度の比として計算され、これは混合物の作業性を示します。

圧縮係数試験

圧縮係数試験は、コンクリートの作業性を評価するために使用される方法です。この試験は、最大 3.81 cm の大きさの骨材を含むコンクリート混合物に特に適しています。この試験には、摩擦を最小限に抑えるために内面が研磨された 2 つの円錐台形のホッパーと 1 つのシリンダーで構成される特殊な装置が使用されます。


 手順は、コンクリートを圧縮せずに上部ホッパーに入れることから始まります。コンクリートが満たされると、このホッパーの下部ドアが開き、コンクリートが下部ホッパーに流れ込みます。下部ホッパーが満たされると、下部ドアが開き、コンクリートがその下にあるシリンダーに落ちます。余分なコンクリートは削り取られ、表面が平らになります。


 試験中、ホッパーに詰まったコンクリートを鋼棒で軽く突いて取り除くことがあります。シリンダー内のコンクリートの重量を記録し、部分的に圧縮されたときの密度を計算します。比較のために、同じシリンダーにコンクリートを 4 層に充填し、各層を徹底的に突き固めて最大限の圧縮を確保することで、コンクリートの完全圧縮密度を測定します。


 圧縮係数は、部分的に圧縮されたコンクリートの密度と完全に圧縮されたコンクリートの密度の比率として計算されます。この比率はコンクリートの作業性を示す数値を提供し、圧縮係数のレベルの違いは作業性の程度の違いを反映します。この試験は、建設プロジェクト中にコンクリートを型枠や型枠に配置したときにコンクリートがどのように動作するかを理解するために重要です。

締固め係数試験は、骨材サイズが最大1.5インチまでのコンクリートの施工性を決定します。
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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

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 bottom door is opened so the mix can flow into the lower hopper.

After the lower hopper fills, its bottom door is opened. The concrete falls into the cylinder below. Extra concrete is struck off to make the surface level. If concrete gets stuck in the hoppers, a steel rod may be used to gently poke it loose.

Next, the weight of the concrete in the cylinder is recorded. This gives the density of the partially compacted concrete. For comparison, the same cylinder is filled with concrete in four layers and each layer is tamped thoroughly to reach maximum compaction. The compacting factor is then calculated as the ratio of the partially compacted density to the fully compacted density. This number shows the workability of the concrete and helps predict how the mix will behave in forms.

Concrete Workability by Compacting Factor

concrete-workability-by-compacting-factor

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

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

Measure concrete workability with the compacting factor test using hoppers and a cylinder. Learn how partially and fully compacted densities are compared.

Concrete Workability by Compacting Factor | 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 by Compacting Factor

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