Name: retarders in concrete pouring
Uploaded: 2024-11-07T14:48:38.000Z
Duration: 1 min 19 s
Channel: JoVE

더운 날씨 콘크리트에서 더 높은 온도로 인해 정상 설정 시간이 단축되면 연속적인 배치 사이에 차가운 조인트가 형성될 수 있습니다.
지연제가 콘크리트에 사용될 때, 처음에 타설된 콘크리트는 새로 타설된 콘크리트 층의 다음 배치와의 응집력을 보장하기 위해 더 오래 플라스틱으로 유지됩니다.
층 간의 응집력은 노출된 골재로 원하는 건축적 마감을 달성하는 데 유리할 수 있습니다.
지연제는 콘크리트의 응결 시간을 연장하는 혼합물이며, 이 지연은 침투 테스트를 사용하여 정량화할 수 있습니다.
콘크리트 응결의 지연 또는 지연은 설탕, 탄수화물 유도체, 용해성 아연염 및 용해성 붕산염과 같은 물질을 통합함으로써 달성할 수 있습니다.
시멘트 질량에 비해 약 0.05%의 설탕을 첨가하면 경화 시간을 약 4시간 연장할 수 있습니다.
지연제는 콘크리트의 결정 성장을 변화시켜 지속적인 수분 공급에 더 효과적인 장애물을 만드는 것으로 여겨집니다.
나중에, 지연제는 최종 수화 제품을 변경하지 않고 구조의 일부가 됩니다.

리타더

Retarders

지연제는 응결 시간을 늘리기 위해 설계된 화학 혼합물로, 특히 연속적인 콘크리트 타설이 지연되어 콜드 조인트를 방지하고 응집력 있는 구조를 달성할 때 유용합니다. 지연제는 적절한 양으로 사용하면 노출된 골재 마감재의 건축적 외관을 향상시킬 수도 있습니다.


 지연제의 기능은 콘크리트의 응결을 지연시키는 것이며, 이 효과는 침투 시험을 사용하여 측정할 수 있습니다. 지연 공정에는 콘크리트 혼합물에 설탕, 탄수화물 유도체, 가용성 아연염 및 붕산염과 같은 물질을 추가하는 것이 포함됩니다. 시멘트 질량 기준으로 설탕의 0.05%와 같은 소량은 응결 시간을 약 4시간 연장할 수 있습니다. 지연제가 콘크리트 내의 결정 성장을 방해하여 수화 과정에 더 강력한 장벽을 생성한다는 가설이 있습니다. 지연제는 초기 강도 발달 속도를 변경하지만 수화 생성물의 최종 구성이나 정체성을 변경하지 않습니다. 지연제를 통합하면 초기 강도가 낮아질 수 있지만 최종 강도에는 영향을 미치지 않으며, 이는 지연되지 않은 콘크리트보다 높을 수 있습니다. 또한 지연제는 확장된 소성 단계로 인해 소성 수축을 증가시키는 것으로 관찰되었지만 건조 수축에는 영향을 미치지 않습니다.

더운 날씨 콘크리트에서 더 높은 온도로 인해 정상 설정 시간이 단축되면 ...

Education

교육

JoVE Core

Civil Engineering

토목공학

Unit 1

제1단원

Admixtures

혼화제

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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, carbohydrate derivatives, soluble zinc salts, and borates.

Even a small amount can make a difference. For example, sugar at 0.05 percent by mass of cement can extend setting by about four hours. Retarders are thought to work by interfering with crystal growth in the concrete, which creates a stronger barrier to hydration.

Retarders change the early rate of strength development, but they do not change the final composition or identity of the hydration products. Concrete may have lower strength at first, yet its ultimate strength is not affected and may even be higher than in concrete without retarders. They can also increase plastic shrinkage because the plastic stage lasts longer, but they do not affect drying shrinkage.

Retarders in Concrete Pouring

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 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 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...

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 retarders delay setting, help prevent cold joints, and affect strength, shrinkage, and exposed aggregate finishes in construction.

Retarders in Concrete Pouring | JoVE K12

JoVE Core Civil Engineering offers a foundational exploration of essential construction materials such as bricks, stones, steel, wood, and concrete, along with fluid mechanics topics like flow over immersed bodies, open channel flow, and dimensional modeling. It also covers key surveying concepts, including leveling, traverse adjustments, curve design, topographic mapping, and geospatial technologies (GPS & GIS). Science-in-action videos showcase laboratory research on materials, fluids, and surveying practices in real-world engineering systems.

civil engineering

Retarders in Concrete Pouring

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