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

フィラーと添加剤は、ポルトランドセメントに似た細粒の材料です。
セメント系添加剤として使用されるポゾランや高炉スラグは、コンクリートの施工性や密度を向上させるとともに、にじみやひび割れを低減します。
フィラーは、炭酸カルシウムを形成する核形成点を提供することにより、ポルトランドセメントの水和プロセスを促進することができます。これらの核形成部位は、フライアッシュと二酸化チタン粒子を含むコンクリートで観察されます。
炭酸カルシウムはケイ酸カルシウム水和物相と融合し、水和するとセメントペーストの構造を有利に変化させます。
フィラーは、天然または加工された無機物質に由来することもでき、主に水和石灰や骨材粉塵などの物理的効果を発揮します。
通常、これらのフィラー材料は、グラウトや石積みモルタルの加工性向上剤として機能します。着色顔料も不活性添加物と見なされます。
粉末状の亜鉛またはアルミニウムを水酸化カルシウムの存在下で導入すると、水素ガスが生成されます。これらの材料は、ガス形成混和剤として知られており、気泡コンクリートを作成します。
別の例である過酸化水素は、砂とセメントの混合物内に保持された酸素気泡を放出して、気泡コンクリートを生成します。

コンクリートの添加剤と充填剤

添加剤と充填剤は、コンクリートの特性を高めるために不可欠です。ポゾランと高炉スラグは、セメントの水和中に放出される水酸化カルシウムと反応するため、添加剤または混和剤となります。充填剤は細かく粉砕され、ポルトランドセメントと同等の細かさで、作業性密度などのコンクリートの特性を向上させ、毛管作用による滲みやひび割れを減らします。充填剤の中には、水硬性特性を持つものや、セメントペースト内で無害な反応に関与するものなどがあります。


 充填剤の役割は、ポルトランドセメントの水和を促進し、核形成部位を提供することです。この役割は、多くの場合、フライアッシュと二酸化チタンによって果たされ、結果として得られるセメントペーストの微細構造に貢献します。充填剤は、一貫した特性、特に細かさを備えた天然または加工されたものを使用できます。充填剤は、水の需要を増やしたり、コンクリートの耐久性と強度に悪影響を与えたりしてはなりません。


 充填剤や添加剤は、主にセメントと物理的に混合され、適合性が必要です。たとえば、初期の強度には、非常に細かいセメント粒子が不可欠です。消石灰や標準重量の骨材などの不活性材料は、強度ではなく作業性を向上させるために添加されます。アルカリや水酸化カルシウムの存在下で水素を放出する添加剤は、ガスコンクリートや気泡コンクリートの製造に使用され、断熱効果があります。過酸化水素などのガス形成混和剤は、気泡コンクリート混合物に酸素泡を生成します。

フィラーと添加剤は、ポルトランドセメントに似た細粒の材料です。
セメント系として使用されるポゾランと高炉スラグ...

Education

JoVE Core

Civil Engineering

土木工学

Unit 1

ユニット1

Admixtures

混和剤

KEY TERMS AND CONCEPTS

主要用語と概念

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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