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

コンクリートの施工性を調べ、流動性の高いコンクリートを評価するために使用されるフローテーブル試験には、鋼板を上に乗せた木の板からなる装置が含まれ、総重量は35ポンドです。
ヒンジがボードをベースに接続し、ボードの各辺のサイズは27.6インチです。
上部ボードは1.6インチの高さまで持ち上げられるように設計されており、テーブルにはコンクリートを配置する場所をガイドする特定のマーキングがあります。
高さ8インチの円錐台、ベースの直径が8インチ、上部の直径が5インチの円錐台がコンクリートで満たされています。やさしく締固められ、余分なコンクリートが取り除かれ、30秒後にコーン型枠が丁寧に取り除かれます。
テーブルは15回揺れ、各揺れは4秒間隔で与えられ、コンクリートが広がります。
テーブルの2つのエッジに平行な広がりの範囲の平均は、衝撃後に測定され、コンクリートの作業性を示し、特定の値は中程度または高い作業性に対応します。

フローテーブル試験

フローテーブル試験は、コンクリートの作業性を評価するために確立された方法であり、特に高流動性コンクリートの混合物の評価に役立ちます。この試験では、木製の板の上に鋼板を載せた、総重量約 15.87 kg の装置を使用します。板はヒンジを介して台座に接続されており、各辺の長さは 70.10 cm です。


 コンクリートは、高さ 20.32 cm、底部の直径 20.32 cm、上部の直径 12.70 cmの円錐台形の型枠内に配置されます。コンクリートは軽く圧縮され、余分な部分は取り除かれ、30 秒後に型枠が取り外されます。


 試験手順では、上部の板を 4.06 cm の高さまで持ち上げ、4 秒間隔でテーブルを 15 回揺らします。この動作により、コンクリートは最初の円錐形から広がります。揺らした後、コンクリートの広がりの程度をテーブルの 2 つの端に平行に測定します。平均広がりを計算してコンクリートの作業性を評価します。広がりの特定の値を使用して、コンクリートの作業性を中程度または高いに分類します。この試験では、コンクリートが自重で流動して沈降する能力に関する重要なデータが得られ、高い流動性と均一な分布が必要なさまざまな建設用途への適合性が反映されます。

コンクリートの施工性を求め、流動性の高いコンクリートを評価するためのフローテーブル試験は、木の板で構成された装置を用いて...

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

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

Description

Transcript