Name: concrete fillers that improve performance
Uploaded: 2024-11-07T14:48:38.000Z
Duration: 1 min 29 s
Channel: JoVE

Cargas e aditivos são materiais de granulação fina com uma finura semelhante ao cimento Portland.
Pozolanos e escória de alto-forno, usados como aditivos cimentícios, melhoram as qualidades do concreto, como trabalhabilidade e densidade, reduzindo o sangramento e as rachaduras.
Os enchimentos podem aumentar o processo de hidratação do cimento Portland, fornecendo pontos de nucleação formando carbonato de cálcio. Esses locais de nucleação são observados em concreto com cinzas volantes e partículas de dióxido de titânio.
O carbonato de cálcio se funde com a fase de hidrato de silicato de cálcio, alterando favoravelmente a estrutura da pasta de cimento uma vez hidratada.
Os enchimentos também podem ser derivados de substâncias inorgânicas naturais ou processadas e exercem principalmente um efeito físico, como cal hidratada ou pó agregado.
Normalmente, esses materiais de enchimento servem como intensificadores de trabalhabilidade em argamassas e argamassas de alvenaria. Os pigmentos de cor também são considerados adições inertes.
Quando o zinco ou alumínio em pó é introduzido na presença de hidróxido de cálcio, ele produz gás hidrogênio. Esses materiais, conhecidos como aditivos formadores de gás, criam concreto aerado.
O peróxido de hidrogênio, outro exemplo, libera bolhas de oxigênio retidas na mistura de areia e cimento para produzir concreto aerado.

aditivos e enchimentos em concreto

Aditivos e enchimentos são essenciais para melhorar as propriedades do concreto. Pozolanas e escória de alto-forno são aditivos ou misturas devido às suas reações com hidróxido de cálcio liberado durante a hidratação do cimento. Os enchimentos, que são finamente moídos e semelhantes em finura ao cimento Portland, melhoram os atributos do concreto, como densidade de trabalhabilidade, e reduzem sangramento capilar ou rachaduras. Alguns enchimentos possuem propriedades hidráulicas ou participam de reações benignas dentro da pasta de cimento.

O papel dos enchimentos é promover a hidratação do cimento Portland, fornecendo locais de nucleação, um papel frequentemente desempenhado por cinzas volantes e dióxido de titânio, que contribuem para a microestrutura da pasta de cimento resultante. Os enchimentos podem ser naturais ou processados, com propriedades consistentes, especialmente a finura. Eles não devem aumentar a demanda de água ou afetar adversamente a durabilidade e resistência do concreto.

Os enchimentos e aditivos são principalmente misturados fisicamente com cimento e devem ser compatíveis. Por exemplo, algumas partículas muito finas de cimento são essenciais para a resistência inicial. Materiais inertes como cal hidratada ou agregados de peso normal são adicionados para melhorar a trabalhabilidade, não a resistência. Aditivos que liberam hidrogênio na presença de álcalis ou hidróxido de cálcio são usados ​​na fabricação de concreto gasoso ou concreto aerado, fornecendo isolamento térmico. Aditivos formadores de gás como peróxido de hidrogênio geram bolhas de oxigênio em misturas de concreto aerado.

Aditivos e enchimentos em concreto

Cargas e aditivos são materiais de granulação fina com uma finura semelhante ao cimento Portland.
Pozolanos e escórias de alto-forno, utilizados como ...

Education

JoVE Core

Civil Engineering

Engenharia Civil

Unit 1

Unidade 1

Admixtures

Aditivos

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

Additives and Fillers in Concrete

concrete fillers that improve performance

Concrete fillers and additives help change how cement paste performs. Pozzolans and blast-furnace slag act as additives or admixtures because they react with calcium hydroxide released during cement hydration. Fine fillers are close in fineness to Portland cement and can improve workability, density, and resistance to capillary bleeding or cracking.

Some fillers are hydraulic, which means they can react with water, while others take part in harmless reactions inside the cement paste. A key role of many fillers is to support Portland cement hydration by giving the paste nucleation sites, or places where new crystals can start forming. Fly ash and titanium dioxide can play this role and help shape the microstructure of the hardened cement paste.

Fillers may be natural or processed, but they should have steady properties, especially fine particle size. They should not raise the water demand of the mix or reduce durability and strength. In concrete, fillers and additives are usually mixed in physically, so they must be compatible with the cement system.

Very fine cement particles can also matter for early strength. Inert materials such as hydrated lime or normal-weight aggregates may be added to improve workability rather than strength. Some additives release hydrogen in the presence of alkalis or calcium hydroxide and are used to make gas concrete, also called aerated concrete, which provides thermal insulation. Gas-forming admixtures such as hydrogen peroxide can create oxygen bubbles in aerated concrete mixes.

Concrete Fillers That Improve Performance

concrete-fillers-that-improve-performance

accelerators

Calcium Chloride in Concrete Mixes

Calcium chloride is a concrete admixture that speeds up hardening and helps concrete gain early strength faster. It does not always change the setting time itself, but it can reduce the time needed in practice. This makes it useful in cold weather and in rapid repair work where quick heat generation after mixing is helpful. A common amount is 1 to 2 percent of the cement mass. Its effect can be compared with raising the concrete temperature by 11 degrees Fahrenheit. To spread it evenly through...

retarders

Retarders in Concrete Pouring

Retarders are chemical admixtures used in concrete to slow the setting time. They are especially helpful when one pour must follow another after a delay. By keeping the concrete workable for longer, they can help prevent cold joints and support a more cohesive structure. Retarders can also improve the look of exposed aggregate finishes when they are used in the right amount. Their effect on setting time can be checked with a penetration test. Common retarding substances include sugar,...

plasticizers

Concrete Workability with Plasticizers

Concrete plasticizers are water-reducing chemical admixtures that improve workability and strength. They help concrete use less water while keeping the same flow, reduce cement content without losing workability, or make mixes easier to place in hard-to-reach areas. Plasticizers work by using surface-active agents. These agents create repulsive electrostatic forces between cement particles. The particles disperse more evenly, and the concrete needs about 5 to 15 percent less mixing water. <br...

superplasticizers

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...

additives and fillers in concrete

Concrete fillers and additives help change how cement paste performs. Pozzolans and blast-furnace slag act as additives or admixtures because they react with calcium hydroxide released during cement hydration. Fine fillers are close in fineness to Portland cement and can improve workability, density, and resistance to capillary bleeding or cracking. Some fillers are hydraulic, which means they can react with water, while others take part in harmless reactions inside the cement paste. A key...

waterproofing and anti-bacterial admixtures in concrete

waterproofing-and-anti-bacterial-admixtures-in-concrete

Concrete Water Resistance and Biological Protection

Concrete can absorb water because of capillary action in the pores of its hydrated cement paste. That movement pulls water into the material. Waterproofing admixtures are added to reduce this penetration and help concrete resist water. The effect of a waterproofing admixture depends on the water pressure acting on the concrete. Rain, capillary rise, and hydrostatic pressure in structures made to hold water can all affect performance. These admixtures make concrete hydrophobic, which means they...

key terms and concepts

Learn how concrete fillers and additives affect workability, density, early strength, cracking, and aerated concrete through simple, science-based examples.

Concrete Fillers That Improve Performance | 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

Concrete Fillers That Improve Performance

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