Name: how cement curing changes porosity
Uploaded: 2024-11-07T14:48:30.000Z
Duration: 1 min 18 s
Channel: JoVE

Wenn frischer Zementleim aushärtet, geht er von einem flüssigen Zustand in eine feste Masse über und schließt Wasser in verschiedenen Formen ein, wie z. B. Gelwasser, Kapillarwasser und gebundenes Wasser.
Gelwasser, das in den Poren des Zementgels eingeschlossen ist, macht in der Regel etwa 28 % des Gesamtvolumens des Zementgels aus.
Etwa 23 % der Masse des trockenen Zements bestehen aus dem gebundenen Wasser, das mit den verschiedenen Produkten verbunden ist, die aus dem Hydratationsprozess hervorgehen.
Wenn der Zementleim mehr Wasser enthält, als für die Hydratation benötigt wird, bildet das überschüssige Wasser Kapillarporen, die etwa 18,5 % des ursprünglichen Zementvolumens ausmachen und oft mit Wasser gefüllt sind.
Das Verhältnis des kombinierten Volumens der Gel- und Kapillarporen zum Gesamtvolumen des Zementleims bestimmt die Gesamtporosität des Zementleims.
Das Wasser-Zement-Verhältnis ist ein entscheidender Faktor, da überschüssiges Wasser mehr Kapillarporen erzeugt, was zu einer höheren Porosität und möglicherweise schwächer ausgehärtetem Zementleim führt.
Die richtige Aushärtung kann die Porosität reduzieren, indem sie eine kontinuierliche Feuchtigkeitsversorgung ermöglicht, die die Kapillarporen mit Feuchtigkeitsprodukten füllt.

porosität in beton

Porosity in Cement Paste

Die Porosität von Beton ist ein Maß für die Hohlräume in seiner Struktur. Diese Hohlräume beeinflussen seine Festigkeit und Haltbarkeit erheblich. Wenn Wasser und Zement miteinander interagieren, entsteht durch eine chemische Reaktion namens Hydratation eine halbfester Leim. Dieser Leim enthält gebundenes Wasser, das etwa 23 % der Trockenmasse des Zements ausmacht, und Gelwasser, das winzige Hohlräume, sogenannte Gelporen, füllt und etwa 28 % des Zementgelvolumens ausmacht.


 Das Verhältnis von Wasser zu Zement in der Mischung ist entscheidend – es beeinflusst das Ausmaß der Hydratation und damit die Porosität und Festigkeit des ausgehärteten Betons. Bei einem idealen Hydratationsprozess bildet sich zusätzlicher Raum, der nicht von festen Hydratationsprodukten eingenommen wird, Kapillarporen, die etwa 18,5 % des ursprünglichen Zementvolumens ausmachen. Während der Beton aushärtet, kann eine kontinuierliche Hydratation die Kapillarporen mit Hydratationsprodukten füllen und so die Dichte des Materials erhöhen.


 Für eine vollständige Hydratation und optimale Festigkeit muss der Aushärtungsprozess sorgfältig gesteuert werden. Er ermöglicht eine zusätzliche Hydratation und reduziert die Porosität, indem die Kapillarräume mit stabileren Hydratationsprodukten gefüllt werden und der Leim dadurch verdichtet wird. Dieser sorgfältige Prozess ist entscheidend für die Herstellung von langlebigem, hochwertigem Beton, der weniger anfällig für Umwelteinflüsse und mechanische Beschädigungen ist.

Porosität in Beton

Wenn frischer Zementleim aushärtet, geht er von einem flüssigen Zustand in eine feste Masse über und schließt Wasser in verschiedenen Formen ein, wie z. B. Gelwasser, Kapillarwasser und ...

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Unit 1

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Strength of Concrete

Betonfestigkeit

KEY TERMS AND CONCEPTS

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how cement curing changes porosity

Cement curing changes porosity in the hardened paste. Porosity means the void spaces inside concrete. These spaces affect both strength and durability. When water and cement react, hydration forms a semi-solid paste that traps water in different ways.

Some of that water becomes combined water. It makes up about 23% of the cement's dry mass. Other water stays as gel water, which fills very small voids called gel pores. Gel pores account for about 28% of the cement gel volume.

The water-to-cement ratio is important in the mix. It controls how much hydration can happen. That, in turn, affects the porosity and strength of the cured concrete. In an ideal hydration process, the space not filled by solid hydration products becomes capillary pores, which are about 18.5% of the original cement volume.

As concrete cures, hydration can continue. More hydration products can fill the capillary pores and make the material denser. Careful curing helps complete this process and reduces porosity. The result is durable, high-quality concrete that is less likely to break down under environmental and mechanical stress.

How Cement Curing Changes Porosity

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How Cracks Limit Concrete Strength

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porosity in cement paste

Cement curing changes porosity in the hardened paste. Porosity means the void spaces inside concrete. These spaces affect both strength and durability. When water and cement react, hydration forms a semi-solid paste that traps water in different ways. Some of that water becomes combined water. It makes up about 23% of the cement's dry mass. Other water stays as gel water, which fills very small voids called gel pores. Gel pores account for about 28% of the cement gel volume. The...

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Concrete Porosity and Durability

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Concrete Strength and Water Balance

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How Mix Ratio Changes Concrete Strength

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Concrete Transition Zone and Its Porosity

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Concrete Fatigue Under Repeated Loads

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How Concrete Is Preloaded for Strength

Prestressed concrete is a construction method that preloads concrete so it can handle more stress. High-strength steel strands are stretched before or after the concrete is loaded in service. The goal is to put the concrete into compression. That compression helps balance the tension the structure will face later. By reducing tension, prestressing helps limit cracks in the concrete. It can also let a structure carry greater loads or span longer distances than conventional reinforced concrete.

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Ferrocement is a construction material made from dense layers of mesh or fine rods covered fully in cement mortar. It is a form of reinforced concrete, but it uses mesh instead of the larger steel bars found in standard reinforced concrete. This structure gives ferrocement its thin, flexible form. The material is built from wire meshes and a mortar made of cement and sand. The mortar is usually mixed in a 1:2 or 1:3 ratio. The water-to-cement ratio is kept between 0.40 and 0.45. This helps the...

non-destructive tests for concrete strength

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key terms and concepts

Learn how hydration, gel water, and capillary pores affect cement paste porosity, strength, and durability as concrete cures.

How Cement Curing Changes Porosity | 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

How Cement Curing Changes Porosity

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