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

Il test del fattore di compattazione determina la lavorabilità del calcestruzzo con dimensioni aggregate fino a un massimo di un pollice e mezzo.
L'apparecchiatura di prova è costituita da due tramogge troncoconiche a forma di cono con porte incernierate nella parte inferiore e un cilindro, il tutto impilato in sequenza, con superfici interne lucidate per ridurre l'attrito.
Il calcestruzzo viene posizionato nella tramoggia superiore senza compattarsi e la porta inferiore viene aperta, lasciando che il calcestruzzo fluisca nella tramoggia inferiore.
Successivamente, viene aperta la porta inferiore della tramoggia inferiore, consentendo al calcestruzzo di cadere nel cilindro sottostante e il calcestruzzo in eccesso viene rimosso.
Un'asta d'acciaio viene utilizzata per colpire e rimuovere delicatamente il calcestruzzo che rimane bloccato in una o entrambe le tramogge durante il test.
Viene determinato il peso finale del calcestruzzo nel volume impostato del cilindro e viene calcolata la densità per questo parzialmente compattato.
La densità completamente compattata viene determinata riempiendo il cilindro di calcestruzzo in quattro strati e rincalzando ogni strato.
Infine, il fattore di compattazione è calcolato come il rapporto tra la densità del calcestruzzo parzialmente compattato e la densità del calcestruzzo completamente compattato, che indica la lavorabilità dell'impasto.

test del fattore di compattazione

Il test del fattore di compattazione è un metodo utilizzato per valutare la lavorabilità del calcestruzzo. È particolarmente adatto per miscele di calcestruzzo contenenti aggregati fino a 38 millimetri di grandezza. Questo test prevede attrezzature specializzate costituite da due tramogge a forma di cono troncato e un cilindro, tutte aventi superfici interne lucidate per ridurre al minimo l'attrito.


 La procedura inizia con il posizionamento del calcestruzzo nella tramoggia superiore senza alcuna compattazione. Una volta riempita, la valvola inferiore di questa tramoggia viene aperta, consentendo al calcestruzzo di fluire nella tramoggia inferiore. Dopo che la tramoggia inferiore è piena, la sua valvola inferiore viene quindi aperta per far cadere il calcestruzzo nel cilindro posizionato sotto di essa. Il calcestruzzo in eccesso viene quindi eliminato per livellare la superficie.


 Durante il test, può essere utilizzata una barra di acciaio per colpire delicatamente e rimuovere del calcestruzzo che potrebbe rimanere incastrato nelle tramogge. Viene poi registrato il peso del calcestruzzo all'interno del cilindro e ne viene calcolata la densità quando parzialmente compattato. Per fare un confronto, la densità del calcestruzzo completamente compattato viene determinata riempiendo di calcestruzzo lo stesso cilindro in quattro strati e pressando accuratamente ogni strato per garantire la massima compattazione.


 Il fattore di compattazione è calcolato come il rapporto tra la densità del calcestruzzo parzialmente compattato e la densità del calcestruzzo completamente compattato. Questo rapporto fornisce un valore numerico che indica la lavorabilità del calcestruzzo, con diversi livelli del fattore di compattazione che riflettono vari gradi di lavorabilità. Questo test è fondamentale per comprendere come si comporterà il calcestruzzo quando verrà posizionato in stampi o casseforme durante i progetti di costruzione.

Test del fattore di compattazione

Il test del fattore di compattazione determina la lavorabilità del calcestruzzo con dimensioni aggregate fino a un massimo di un pollice e mezzo.
L'apparecchiatura di prova ...

Education

Didattica

JoVE Core

Civil Engineering

Ingegneria Civile

Unit 1

Unità 1

Fresh Concrete

Calcestruzzo fresco

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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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