Name: how aggregate shape affects concrete bond
Uploaded: 2024-09-12T16:16:39.000Z
Duration: 1 min 12 s
Channel: JoVE

The strength of a concrete mix made of rough and angular aggregates is higher than that of smooth and rounded aggregates.
This is because a rough surface offers better bonding with cement particles than a smooth surface.
Additionally, compared to round aggregates, angular aggregates offer a larger surface area to adhere to for cement paste, and better interlocking exists between the aggregates.&#160;
A strong bond in concrete is indicated by some aggregates breaking through and others detaching cleanly from the paste matrix during crushing.
When a concrete section is loaded, the stress at the contact points of aggregates is higher than the overall stress on the concrete, necessitating aggregates with strength greater than the concrete mix itself.
At the same time, when concrete undergoes volume changes and aggregates within it are too rigid, the stresses developed in the cement paste around the aggregate can lead to cracks in the cement paste.
The strength of aggregates can be determined indirectly by testing the parent rock sample or a bulk aggregate sample.

binding en sterkte van aggregaat

De binding tussen aggregaat deeltjes en de cementmatrix wordt aanzienlijk beïnvloed door de vorm en oppervlaktetextuur van de aggregaten. Beton met een hoge sterkte profiteert van een ruwere textuur, wat leidt tot een sterkere binding door een grotere hechting. Hoekige aggregaten met grotere oppervlakken verbeteren deze binding ook. De binding kwaliteit is echter complex om te beoordelen, aangezien er geen universeel geaccepteerde test bestaat. Een goede binding is aangegeven wanneer een gebroken betonmonster enkele aggregaat deeltjes vertoont die door en door gebroken zijn en de meeste van de matrix gescheiden zijn.

De sterkte van beton wordt voornamelijk bepaald door de aggregaat sterkte, aangezien de druksterkte van beton de sterkte van het grootste deel van het aggregaat dat het bevat niet kan overtreffen. Informatie over de sterkte van het aggregaat wordt doorgaans afgeleid van indirecte tests, zoals de breekwaarde van bulk aggregaat en de breeksterkte van gesteentemonsters waaruit de aggregaten zijn afgeleid. Uit onderzoek is gebleken dat toeslagmaterialen met een hoge sterkte bijdragen aan de algehele sterkte, terwijl toeslagmaterialen met een matige of lage sterkte juist gunstig zijn voor de structurele integriteit van beton. Deze toeslagmaterialen kunnen namelijk worden samengedrukt bij thermische of hygrische veranderingen, waardoor de spanning op de cementpasta afneemt en scheuren worden voorkomen.

Binding en sterkte van aggregaat

The strength of a concrete mix made of rough and angular aggregates is higher than that of smooth and rounded aggregates.
This is because a rough surface ...

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JoVE Core

Civil Engineering

Civiele techniek

Unit 1

Aggregates and Water

Aggregaten en water

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

Bonding and Strength of Aggregate

how aggregate shape affects concrete bond

Aggregate shape and surface texture affect how well concrete holds together. Rough, angular aggregates usually bond more strongly with the cement matrix than smooth, rounded ones. This stronger adhesion can help produce high-strength concrete.

Angular aggregates also have a larger surface area. That gives the cement paste more area to grip, which improves the bond. Bond quality is hard to measure directly, and there is no single test that is accepted everywhere.

A broken concrete sample can give a clue about bond quality. Good bonding is often seen when some aggregate particles are fractured through the piece. Most of the particles should also separate from the matrix after crushing.

Concrete strength depends mostly on the strength of the aggregate itself. The compressive strength of concrete cannot be higher than the strength of most of the aggregate inside it. Engineers usually estimate aggregate strength with indirect tests, such as bulk aggregate crushing value tests and crushing strength tests on the source rock.

High-strength aggregates can raise overall concrete strength. Still, aggregates with moderate or lower strength can also be useful in a structure. They may compress during thermal or hygral changes, which reduces stress on the cement paste and helps prevent cracking.

How Aggregate Shape Affects Concrete Bond

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maximum size of aggregate

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quality of water

Water Standards for Concrete Mixing

Water standards for concrete mixing help control strength and durability. Potable water is usually preferred. Even so, it should not contain too much sodium or potassium, because these salts can weaken concrete integrity. Water quality is judged by impurities such as dissolved solids, chlorides, and sulfates. The pH value is ideally between 6 and 8. Slightly acidic natural water may still be acceptable if it does not contain harmful organic matter or algae. Limits for these impurities depend...

testing water quality

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bonding and strength of aggregate

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specific gravity of aggregate

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Aggregate specific gravity depends on the pores inside the material. These pores may be permeable or impermeable, so the same aggregate can be described in more than one way. For this reason, specific gravity is grouped into bulk or gross specific gravity, apparent specific gravity, and absolute specific gravity. Bulk or gross specific gravity uses the mass of aggregate in the saturated surface-dry state. It is compared with the total volume of the aggregate, including both the solids and the...

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How Aggregate Moisture Affects Concrete Mixes

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key terms and concepts

Learn how rough, angular aggregates improve bonding in concrete, how bond quality is checked, and why aggregate strength limits concrete strength.

How Aggregate Shape Affects Concrete Bond | 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.

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How Aggregate Shape Affects Concrete Bond

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