6.6
Test du facteur de compactage
L'essai de facteur de compactage est une méthode utilisée pour évaluer l’ouvrabilité du béton. Il est particulièrement adapté aux mélanges de béton co…
L’essai du facteur de compactage détermine la maniabilité du béton avec des granulats allant jusqu’à un pouce et demi maximum.
L’équipement d’essai se compose de deux trémies tronquées en forme de cône avec des portes à charnières au bas et d’un cylindre, le tout empilé séquentiellement, avec des surfaces intérieures polies pour réduire la friction.
Le béton est placé dans la trémie supérieure sans compactage, et la porte inférieure est ouverte, laissant le béton s’écouler dans la trémie inférieure.
Ensuite, la porte inférieure de la trémie inférieure est ouverte, ce qui permet au béton de tomber dans le cylindre situé en dessous, et l’excès de béton est frappé.
Une tige d’acier est utilisée pour piquer et déloger doucement le béton qui se coince dans l’une ou les deux trémies pendant l’essai.
Le poids final du béton dans le volume de prise du cylindre est déterminé et la masse volumique de ce béton partiellement compacté est calculée.
La densité entièrement compactée est déterminée en remplissant le cylindre de béton en quatre couches et en tapotant chaque couche.
Enfin, le facteur de compactage est calculé comme le rapport entre la masse volumique du béton partiellement compacté et la masse volumique du béton entièrement compacté, ce qui indique la maniabilité du mélange.
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Q1: What is the compacting factor test used for in concrete testing?
The compacting factor test assesses the workability of concrete, indicating how easily concrete flows and compacts. It measures the ratio of partially compacted concrete density to fully compacted density, providing a numerical value that reflects the concrete's ability to be placed and consolidated in molds during construction projects.
Q2: What equipment is needed to perform a compacting factor test?
The test requires two truncated cone-shaped hoppers with hinged bottom doors, a cylinder for collection, and a steel rod. All equipment has polished interior surfaces to minimize friction and allow concrete to flow freely between components during the test procedure.
Q3: How is the compacting factor value calculated?
The compacting factor is calculated as the ratio of the density of partially compacted concrete to the density of fully compacted concrete. Partially compacted density is obtained from concrete falling through hoppers into a cylinder, while fully compacted density is determined by filling the cylinder in four layers and tamping each layer thoroughly.
Q4: What concrete aggregate sizes are suitable for the compacting factor test?
The compacting factor test is suitable for concrete mixes containing aggregates with a maximum size of one and a half inches. This size limitation ensures the concrete flows properly through the hopper system and provides reliable workability measurements for the specified aggregate range.
Q5: What steps are involved in performing the compacting factor test procedure?
Concrete is placed in the upper hopper without compaction. The bottom door opens, allowing concrete to flow into the lower hopper. The lower hopper door then opens, letting concrete fall into the cylinder below. Excess concrete is struck off, and a steel rod dislodges any stuck material. The cylinder weight is recorded to calculate partially compacted density.
Q6: Why are polished interior surfaces important in compacting factor test equipment?
Polished interior surfaces reduce friction between the concrete and equipment, allowing the concrete to flow freely and naturally through the hoppers and into the cylinder. This minimizes artificial resistance and ensures the test accurately reflects the concrete's true workability characteristics without equipment interference.
Q7: How does the compacting factor test differ from determining fully compacted concrete density?
The compacting factor test measures partially compacted density by allowing concrete to fall freely through hoppers, simulating natural placement conditions. Fully compacted density is determined separately by deliberately filling the cylinder in four layers and tamping each layer to achieve maximum compaction, providing a baseline for comparison.