6.8
Teste de mesa de fluxo
O teste de mesa de fluxo é um método estabelecido usado para avaliar a trabalhabilidade do concreto, particularmente útil para avaliar misturas de con…
O teste da mesa de fluxo, usado para encontrar a trabalhabilidade do concreto e avaliar o concreto altamente fluido, envolve um aparelho que consiste em uma placa de madeira coberta com uma placa de aço, com um peso total de 35 libras.
Uma dobradiça conecta a placa a uma base, com cada lado da placa medindo 27,6 polegadas.
A placa superior foi projetada para ser levantada a uma altura de 1,6 polegadas, e a mesa possui marcações específicas que orientam onde o concreto deve ser colocado.
Um cone truncado de 8 polegadas de altura, com um diâmetro de base de 8 polegadas e um diâmetro superior de 5 polegadas, é preenchido com concreto. É compactado suavemente, o excesso de concreto é removido e o molde do cone é cuidadosamente removido após 30 segundos.
A mesa é sacudida 15 vezes, com cada solavanco dado em um intervalo de 4 segundos, fazendo com que o concreto se espalhe.
A média da extensão do espalhamento paralelo às duas bordas da mesa, medida após o solavanco, indica a trabalhabilidade do concreto, com valores específicos correspondentes a média ou alta trabalhabilidade.
View the full transcript and gain access to JoVE Core videos
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.