Name: superplasticizers for stronger concrete mixes
Uploaded: 2024-11-07T14:48:38.000Z
Duration: 1 min 30 s
Channel: JoVE

Os superplastificantes são usados para preparar concreto fluido que pode ser facilmente colocado em arranjos de reforço densos dentro de um molde ou para colocação rápida em pisos e pavimentos.
Alguns superplastificantes são tipicamente formaldeído de melamina sulfonado ou condensado de formaldeído naftaleno sulfonado, com uma dosagem de cerca de 0,2 a 0,6 galões por metro cúbico de concreto.
Os superplastificantes aumentam a dispersão do cimento, fazendo com que o ácido sulfônico seja absorvido pelas superfícies das partículas de cimento, que se tornam carregadas negativamente e se repelem.
Essa ação melhora a trabalhabilidade do concreto para a proporção água-cimento mantida, muitas vezes aumentando o abatimento de 3 para 8 polegadas.
O agregado miúdo é aumentado em 4 a 5 por cento para concreto fluido, e agregados alongados, escamosos ou muito angulares são evitados para evitar segregação e sangramento.
É importante considerar que esse concreto pode exercer pressão hidrostática na fôrma.
Os superplastificantes podem reduzir o uso de água em 25 a 35%, permitindo baixas proporções de água para cimento e permitindo que o concreto atinja resistências de até 15.000 psi em 28 dias.
Os superplastificantes são adicionados ao concreto logo antes da colocação do concreto porque a trabalhabilidade aprimorada dos superplastificantes é temporária.

superplastificantes

Superplasticizers

Superplastificantes são aditivos avançados que melhoram a trabalhabilidade do concreto ao reduzir o teor de água sem comprometer a resistência do material. Essas substâncias são redutores de água altamente eficazes, melhorando o fluxo do concreto, tornando-o mais fácil de trabalhar e permitindo que ele alcance áreas inacessíveis ou seções densamente reforçadas sem vibração mecânica. Os principais componentes dos superplastificantes são condensados ​​de melamina sulfonada ou naftaleno formaldeído, que induzem uma carga negativa nas partículas de cimento, levando à repulsão mútua e dispersando-as dentro da mistura.

A incorporação de superplastificantes no concreto aumenta o abatimento significativamente, permitindo que a mistura permaneça coesa, evitando os problemas de segregação e sangramento. Essa propriedade é especialmente benéfica para a criação de concreto de alta resistência com baixas proporções de água para cimento. Ao reduzir o teor de água em 25 a 35 por cento, podem ser alcançadas resistências do concreto de até 1054,60 Kgf/cm^2 após 28 dias. No entanto, a trabalhabilidade melhorada oferecida pelos superplastificantes é de curta duração, geralmente durando cerca de 30 a 90 minutos, o que requer um tempo preciso em sua adição à mistura de concreto pouco antes da colocação. Embora a redosagem de superplastificantes geralmente não seja recomendada, ajustes podem ser feitos para manter a trabalhabilidade por um tempo limitado. Apesar de seu alto custo, os superplastificantes são valiosos por sua capacidade de produzir concreto durável e de alta resistência de forma eficiente.

Superplastificantes

Os superplastificantes são usados para preparar concreto fluido que pode ser facilmente colocado em arranjos de reforço densos dentro de um molde ou para colocação rápida em ...

Education

JoVE Core

Civil Engineering

Engenharia Civil

Unit 1

Unidade 1

Admixtures

Aditivos

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

superplasticizers for stronger concrete mixes

Superplasticizers are concrete admixtures that make mixes flow better while using less water. They are strong water reducers, so concrete can be easier to place without losing strength. This makes them useful when concrete must reach tight spaces or heavily reinforced areas without mechanical vibration.

These admixtures work through sulfonated melamine or naphthalene formaldehyde condensates. These chemicals give cement particles a negative charge. The particles repel each other and spread out in the mix. As a result, the concrete slump increases, but the mix stays cohesive.

Superplasticizers also help prevent segregation and bleeding. Segregation is when the parts of a concrete mix separate. Bleeding is when water rises to the surface. By lowering water content by about 25 to 35 percent, superplasticizers can support high-strength concrete with low water-to-cement ratios.

The strength gains can be large. Concrete made with superplasticizers can reach up to 15,000 pounds per square inch after 28 days. Their workability is temporary, though. The effect usually lasts only 30 to 90 minutes, so they must be added just before placement.

Re-dosing superplasticizers is generally not recommended, but limited adjustments can help keep the mix workable for a short time. Even though they are expensive, they are valuable for making durable, high-strength concrete efficiently.

Superplasticizers for Stronger Concrete Mixes

superplasticizers-for-stronger-concrete-mixes

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superplasticizers

Superplasticizers are concrete admixtures that make mixes flow better while using less water. They are strong water reducers, so concrete can be easier to place without losing strength. This makes them useful when concrete must reach tight spaces or heavily reinforced areas without mechanical vibration. These admixtures work through sulfonated melamine or naphthalene formaldehyde condensates. These chemicals give cement particles a negative charge. The particles repel each other and spread out...

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key terms and concepts

Learn how superplasticizers improve concrete flow, reduce water content, and support high-strength mixes for dense reinforcement and hard-to-reach areas.

Superplasticizers for Stronger Concrete Mixes | 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

Superplasticizers for Stronger Concrete Mixes

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