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Prova della tavola a scosse
La prova della tavola a scosse è un metodo consolidato utilizzato per valutare la lavorabilità del calcestruzzo, particolarmente utile per valutare mi…
Il test della tavola di flusso, utilizzato per trovare la lavorabilità del calcestruzzo e valutare il calcestruzzo altamente scorrevole, prevede un apparato costituito da una tavola di legno sormontata da una piastra di acciaio, con un peso totale di 35 libbre.
Una cerniera collega la tavola a una base, con ogni lato della tavola che misura 27,6 pollici.
Il pannello superiore è progettato per essere sollevato a un'altezza di 1,6 pollici e il tavolo ha segni specifici che guidano dove deve essere posizionato il cemento.
Un tronco di cono alto 8 pollici, con un diametro di base di 8 pollici e un diametro superiore di 5 pollici, è riempito di cemento. Viene compattato delicatamente, il calcestruzzo in eccesso viene rimosso e lo stampo del cono viene rimosso con cura dopo 30 secondi.
Il tavolo viene scosso 15 volte, con ogni scossa data a un intervallo di 4 secondi, provocando la diffusione del cemento.
La media dell'estensione di diffusione parallela ai due spigoli della tavola, misurata dopo la scossa di scossa, indica la lavorabilità del calcestruzzo, con valori specifici corrispondenti a lavorabilità media o alta.
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Q1: What is the flow table test used for in concrete testing?
The flow table test assesses the workability of concrete, particularly for highly flowable mixes. It measures how easily concrete spreads and flows under controlled jolting, providing data on the concrete's ability to settle under its own weight. This information determines suitability for construction applications requiring high fluidity and even distribution.
Q2: What are the key components of a flow table apparatus?
The flow table apparatus consists of a wooden board topped with a steel plate, weighing 35 pounds total. The board measures 27.6 inches on each side and connects to a base via a hinge. The upper board lifts to 1.6 inches height during testing. A truncated cone mold, 8 inches high with an 8-inch base and 5-inch top diameter, holds the concrete sample.
Q3: How is concrete prepared and placed in the flow table test?
Concrete is placed in the truncated cone mold and gently compacted to ensure uniform density. Excess concrete is carefully cleared away from the top of the mold. After 30 seconds, the cone mold is carefully removed, leaving the concrete sample on the steel plate ready for jolting.
Q4: What happens during the jolting phase of the flow table test?
The table is jolted 15 times at 4-second intervals by lifting the upper board to 1.6 inches and releasing it. Each jolt causes the concrete to spread outward from its initial cone shape. The controlled jolting simulates the effects of vibration during concrete placement in construction applications.
Q5: How is concrete workability determined from flow table test results?
After jolting completes, the extent of concrete spread is measured parallel to the two edges of the table. The average of these two measurements indicates the concrete's workability. Specific spread values categorize the concrete as having medium or high workability, reflecting its flow characteristics.
Q6: Why is measuring concrete spread important for construction?
Measuring concrete spread reveals how well the material flows and distributes under its own weight. This data ensures the concrete meets project requirements for fluidity and even placement. Understanding spread behavior helps prevent segregation and ensures proper concrete consolidation in structural elements.
Q7: How does the flow table test differ from other concrete workability assessments?
The flow table test specifically evaluates highly flowable concrete through controlled jolting and spread measurement. Unlike other workability tests, it simulates vibration effects during placement. This method provides precise quantitative data on concrete flow behavior, making it ideal for self-consolidating and high-performance concrete mixes.