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Prueba de tabla de flujo
La prueba de mesa de flujo es un método establecido que se utiliza para evaluar la trabajabilidad del hormigón, particularmente útil para evaluar mezc…
La prueba de la mesa de flujo, utilizada para encontrar la trabajabilidad del concreto y evaluar el concreto altamente fluido, involucra un aparato que consiste en una tabla de madera cubierta con una placa de acero, con un peso total de 35 libras.
Una bisagra conecta la placa a una base, y cada lado de la tabla mide 27,6 pulgadas.
La tabla superior está diseñada para elevarse a una altura de 1,6 pulgadas, y la mesa tiene marcas específicas que guían dónde se debe colocar el hormigón.
Un cono truncado de 8 pulgadas de alto, con un diámetro de base de 8 pulgadas y un diámetro superior de 5 pulgadas, se rellena con hormigón. Se compacta suavemente, se elimina el exceso de hormigón y el molde cónico se retira con cuidado después de 30 segundos.
La mesa se sacude 15 veces, y cada sacudida se da a un intervalo de 4 segundos, lo que hace que el concreto se extienda.
El promedio del grado de esparcimiento paralelo a los dos bordes de la mesa, medido después de la sacudida, indica la trabajabilidad del hormigón, con valores específicos correspondientes a una trabajabilidad 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.