Podcast
Questions and Answers
Which type of aggregate exhibits the highest percentage of voids?
Which type of aggregate exhibits the highest percentage of voids?
What is the primary reason why elongated aggregates are not suitable for high-strength concrete?
What is the primary reason why elongated aggregates are not suitable for high-strength concrete?
What is the characteristic of flaky aggregates?
What is the characteristic of flaky aggregates?
Which type of aggregate is obtained by crushing rocks?
Which type of aggregate is obtained by crushing rocks?
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What is the term for the size distribution of aggregates?
What is the term for the size distribution of aggregates?
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What is the approximate percentage of total volume of concrete that aggregates make up?
What is the approximate percentage of total volume of concrete that aggregates make up?
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Which of the following is NOT a characteristic of rounded aggregates?
Which of the following is NOT a characteristic of rounded aggregates?
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What is the term for the process of extracting aggregates from underwater sources?
What is the term for the process of extracting aggregates from underwater sources?
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Which type of aggregate is formed from crushed concrete, bituminous or demolition debris?
Which type of aggregate is formed from crushed concrete, bituminous or demolition debris?
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What is the name of the process of breaking down bedrock into smaller particles?
What is the name of the process of breaking down bedrock into smaller particles?
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Study Notes
Types of Aggregates
- Elongated aggregates: length > 180% of mean dimension, poor interlocking behavior, weak bond strength
- Flaky aggregates: thickness < 60% of mean dimension, poor interlocking behavior, weak bond strength
- Irregular aggregates: partially rounded, result in 35-37% voids, lesser workability, slightly higher bond strength
- Angular aggregates: well-defined edges, formed by crushing rocks, result in 38-45% voids, less workability, stronger aggregate-mortar bond
Classification of Aggregates
- Based on size: fine aggregates, coarse aggregates
- Fine Aggregates: sand and/or crushed stone
- Coarse Aggregates: gravel and crushed stone
Definition of Aggregates
- Mineral particles originating from rocks
- Inert filler materials used in making concrete
- Make up 60-75% of total volume of concrete (normal/ordinary concrete), 90% of asphalt pavements
Aggregate Sources
- Natural Aggregate: sand and gravel mine (pit), quarry (bedrock)
- Contrived Aggregate: recycled products, crushed concrete, bituminous, demolition debris, taconite tailings
Methods of Extraction and Processing
- Underwater Sources: dragline excavation, dredging
- Land Sources: track drills, blasting bedrock, crushers and screens
Classification of Aggregates Based on Shape
- Rounded aggregates: completely shaped by attrition, minimum voids (32-33%), more workability, lesser water-cement ratio
- Irregular or partly rounded aggregates: partly shaped by attrition, available in pit sands and gravel
- Angular aggregates: well-defined edges, formed by crushing rocks
- Flaky aggregates: thickness < 60% of mean dimension
- Elongated aggregate: length > 180% of mean dimension
- Flaky and elongated aggregates: combination of flaky and elongated shapes
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Description
Identify and understand the different types of aggregates, including elongated and flaky aggregates, and their effects on concrete strength.
