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

La porosità dell'aggregato si riferisce al volume dei pori nell'aggregato.
Questi pori variano in dimensioni e sono racchiusi all'interno dell'aggregato o interconnessi e aperti sulla sua superficie, attraverso la quale l'acqua o altri fluidi possono entrare negli aggregati.
Uno stato superficiale saturo e secco implica che tutti i pori dell'aggregato sono pieni di umidità, ma la superficie è asciutta.
Nel frattempo, uno stato umido indica la presenza di umidità in eccesso sulla superficie dell'aggregato saturo.
Quando l'aggregato in uno stato saturo di superficie secca è esposto all'aria, parte dell'umidità evapora dai pori, risultando in uno stato di essiccazione all'aria.
Una volta essiccata in forno, l'umidità completa evapora dai pori dell'aggregato, il che significa uno stato di secchezza ossea.
L'assorbimento d'acqua è calcolato come la differenza nella massa dell'aggregato tra lo stato superficiale saturo e lo stato secco osseo, espressa in percentuale della massa secca del campione.
Infine, l'acqua assorbita nei pori degli aggregati nel calcestruzzo non sarà disponibile per idratare il cemento o migliorare la lavorabilità del calcestruzzo.
Inoltre, se sottoposta a cicli di gelo-disgelo, l'acqua assorbita può causare la disgregazione dell'aggregato.

porosità e assorbimento degli aggregati

Porosity and Absorption of Aggregate

Gli aggregati contengono pori di dimensioni variabili; mentre alcuni sono completamente racchiusi nelle particelle, altri si aprono sulla superficie, consentendo all'acqua di penetrare. La porosità degli aggregati è un fattore importante che contribuisce alla porosità complessiva del calcestruzzo, dato che gli aggregati costituiscono circa tre quarti del volume del calcestruzzo.

Quando tutti i pori di un aggregato sono riempiti d'acqua, l'aggregato è considerato saturo e asciutto in superficie. Se lasciato all'aria secca, l'acqua evaporerà fino a quando l'aggregato non raggiunge uno stato di essiccazione all'aria. L'essiccazione prolungata in un forno asciuga tutta l'umidità, portando a uno stato di essiccazione completa.

L'assorbimento d'acqua, una proprietà critica degli aggregati, è misurato dalla perdita di peso di un campione saturo e asciutto in superficie dopo essere stato essiccato in forno per 24 ore ed è espresso come una percentuale di diminuzione della massa rispetto alla massa secca dell'aggregato. Tuttavia, una durata più realistica per misurare l'assorbimento d'acqua in scenari pratici è di 10-30 minuti anziché 24 ore. Questa modifica riconosce che in contesti di costruzione reali, l'assorbimento effettivo da parte degli aggregati nel miscelatore è inferiore ed è anche influenzato dalla sequenza di aggiunta degli ingredienti. Inoltre, l'acqua assorbita nei pori degli aggregati potrebbe non contribuire all'idratazione del cemento e alla lavorabilità del calcestruzzo.

Porosità e assorbimento degli aggregati

La porosità dell'aggregato si riferisce al volume dei pori nell'aggregato.
Questi pori variano in dimensioni e sono racchiusi all'interno dell'aggregato o ...

Education

Didattica

JoVE Core

Civil Engineering

Ingegneria Civile

Unit 1

Unità 1

Aggregates and Water

Aggregati e acqua

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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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porosity and absorption of aggregate

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...

moisture content and bulking of aggregate

moisture-content-and-bulking-of-aggregate

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key terms and concepts

Learn how aggregate pores affect concrete, and how saturation, air-dry, and oven-dry states relate to water absorption in construction materials.

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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