Name: concrete workability with plasticizers
Uploaded: 2024-11-07T14:48:38.000Z
Duration: 1 min 31 s
Channel: JoVE

Consider concreting in locations that are difficult to access in a mold. Plasticizers help concrete compact on its own, enhancing workability with less water or cement.
Common plasticizers include lignosulfonic acids and hydroxylated carboxylic acids, functioning as water-reducing admixtures that can cut water use by 5 to 15 percent in concrete.
The surface-active agents in plasticizers alter the interfacial forces between non-mixing phases and adhere to cement particles, imparting a negative charge, fostering repulsion, and stabilizing their dispersion while repelling air bubbles.
The negative charge induces a layer of aligned water molecules around each particle, effectively distancing them.
Lastly, particle movement is enhanced, and water is liberated from the clustered system, making it available to ease the mix and improve workability.
Plasticizers enhance the dispersal of cement particles, increasing the surface area for hydration. This dispersion boosts early-age strength relative to mixes without admixtures.
These admixtures&#39;&#160;impact on strength is more pronounced in cements with low tricalcium aluminate or low alkali levels.
Before using plasticizers in construction, testing is essential to identify issues like segregation, bleeding, or reduced workability.

weekmakers

Waterreducerende middelen, of weekmakers, zijn chemische toevoegingen die in beton worden gebruikt om de sterkte en verwerkbaarheid te verbeteren. Deze toevoegingen verlagen de water-cement verhouding zonder de verwerkbaarheid in gevaar te brengen, verlagen het cementgehalte terwijl dezelfde verwerkbaarheid behouden blijft, of verhogen de verwerkbaarheid om beton te helpen plaatsen op ontoegankelijke plekken.

Weekmakers werken door oppervlakteactieve stoffen te gebruiken om afstotende elektrostatische krachten tussen cementdeeltjes te creëren. Deze dispersie verbetert de verwerkbaarheid van het beton en vermindert de noodzaak om water te mengen met 5 tot 15 procent. Ondanks de vertraging van de uithardingstijd met bepaalde weekmakers, wordt het verlies aan verwerkbaarheid in de loop van de tijd niet noodzakelijkerwijs verminderd. Het is belangrijk om proef mengsels te hebben om de compatibiliteit met luchtbelvormers te garanderen, die luchtzakken kunnen introduceren die de uiteindelijke eigenschappen van het beton beïnvloeden.

Deze toevoegingen verbeteren de sterkte van beton, met name in de beginfase, vanwege de gelijkmatigere hydratatie van cement. Ze zijn over het algemeen effectief voor alle cementsoorten, met een meer uitgesproken sterke toename in cement met een laag tricalciumaluminaat- of alkaligehalte. Correct gebruik van waterreducerende middelen kan ook de duurzaamheid van het beton verbeteren. Echter, vóór de implementatie is het van cruciaal belang om te testen op mogelijke negatieve effecten zoals segregatie of bloeding om de levensvatbaarheid van de betonconstructie op de lange termijn te garanderen.

Weekmakers

Consider concreting in locations that are difficult to access in a mold. Plasticizers help concrete compact on its own, enhancing workability with less ...

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JoVE Core

Civil Engineering

Civiele techniek

Unit 1

Admixtures

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN BEGRIPPEN

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.

Some plasticizers can delay setting time. Even so, the loss of workability over time is not always reduced. Trial mixes are important to check compatibility with air-entraining agents, which add air pockets that can change the final properties of the concrete.

These admixtures also improve strength, especially early strength, because cement hydrates more uniformly. They are generally effective with all cement types, but the strength gain is often greater in cements with low tricalcium aluminate or low alkali content. When used correctly, water-reducers can also improve durability.

Before using them in a structure, engineers must test for side effects such as segregation or bleeding. Segregation happens when the mix separates, and bleeding is the rise of water to the surface. These checks help confirm that the concrete will perform well over time.

Concrete Workability with Plasticizers

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 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 plasticizers reduce water use, improve concrete workability, and boost strength. See why trial mixes and compatibility tests matter.

Concrete Workability with Plasticizers | 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 Workability with Plasticizers

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