Name: aggregate pore states and water uptake
Uploaded: 2024-09-12T16:16:40.000Z
Duration: 1 min 20 s
Channel: JoVE

La porosité de l’agrégat fait référence au volume des pores de l’agrégat.
Ces pores varient en taille et sont soit enfermés dans l’agrégat, soit interconnectés et ouverts à sa surface, par laquelle l’eau ou d’autres fluides peuvent pénétrer dans les agrégats.
Un état de surface sèche saturée implique que tous les pores de l’agrégat sont remplis d’humidité, mais que la surface est sèche.
Pendant ce temps, un état humide indique la présence d’un excès d’humidité à la surface de l’agrégat saturé.
Lorsque les agrégats à l’état saturé et sec sont exposés à l’air, une partie de l’humidité s’évapore des pores, ce qui entraîne un état sec à l’air.
Lorsqu’il est séché au four, toute l’humidité s’évapore des pores de l’agrégat, ce qui signifie un état sec.
L'absorption d'eau est calculée comme la différence de masse de l'agrégat entre l'état sec de surface saturé et l'état sec d'os, exprimée en pourcentage de la masse sèche de l'échantillon.
Enfin, l’eau absorbée dans les pores des agrégats du béton ne sera pas disponible pour hydrater le ciment ou améliorer la maniabilité du béton.
De plus, lorsqu’elle est soumise à des cycles de gel-dégel, cette eau absorbée peut provoquer la désintégration de l’agrégat.

porosité et absorption des agrégats

Porosity and Absorption of Aggregate

Les agrégats contiennent des pores de différentes tailles ; certains sont complètement enfermés dans les particules, tandis que d'autres s'ouvrent à la surface, permettant à l'eau de pénétrer. La porosité des agrégats est un facteur majeur contribuant à la porosité globale du béton, étant donné que les agrégats constituent environ les trois quarts du volume du béton.

Lorsque tous les pores d'un agrégat sont remplis d'eau, l'agrégat est considéré comme saturé et sec en surface. S'il est laissé à l'air sec, l'eau s'évapore jusqu'à ce que l'agrégat atteigne un état sec à l'air. Un séchage prolongé dans un four élimine toute l'humidité, ce qui conduit à un état sec ou sec au four.

L'absorption d'eau, une propriété critique des agrégats, est mesurée par la perte de poids d'un échantillon saturé et sec en surface après avoir été séché au four pendant 24 heures et est exprimée en pourcentage de diminution de masse par rapport à la masse sèche de l'agrégat. Cependant, une durée plus réaliste pour mesurer l'absorption d'eau dans des scénarios pratiques est de 10 à 30 minutes plutôt que 24 heures. Cet ajustement tient compte du fait que dans les conditions de construction réelles, l'absorption des granulats dans le malaxeur est généralement moindre, et elle est également influencée par la séquence d'ajout des ingrédients. De plus, l'eau absorbée dans les pores des granulats peut ne pas contribuer à l'hydratation du ciment et à la maniabilité du béton.

Porosité et absorption des agrégats

La porosité de l’agrégat fait référence au volume des pores de l’agrégat.
Ces pores varient en taille et sont soit enfermés dans l’agrégat, soit ...

Education

Enseignement

JoVE Core

Civil Engineering

Génie civil

Unit 1

Unité 1

Aggregates and Water

Granulats et eau

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

aggregate pore states and water uptake

Aggregate contains pores of different sizes, and those pores may be sealed inside the particle or open to the surface. Open pores let water enter the aggregate. Because aggregate makes up about three-quarters of concrete by volume, its porosity strongly affects the porosity of the finished concrete.

Aggregate can also be described by its moisture state. When water fills every pore, the material is saturated and surface-dry. If it sits in dry air, some water evaporates and the aggregate becomes air-dry. After long drying in an oven, no moisture remains, and the sample is bone-dry, or oven-dry.

Water absorption is an important aggregate property. It is measured by finding the weight loss of a saturated, surface-dry sample after it has been oven-dried for 24 hours. The result is reported as a percentage decrease in mass compared with the dry mass of the aggregate.

In practice, a shorter absorption time of about 10 to 30 minutes is often more realistic. In a mixer, aggregates absorb less water than they do in a long drying test, and the result also depends on the order in which materials are added. Water held in aggregate pores may not help cement hydration or improve concrete workability.

Aggregate Pore States and Water Uptake

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key terms and concepts

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Aggregate Pore States and Water Uptake | 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

Aggregate Pore States and Water Uptake

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