LESSON 4

• Aggregates generally refers to mineral particles which have rocks as their origin unless otherwise specified.
• Aggregate are the inert filler materials, such as sand or gravel, used in making concrete
• Aggregates make up 60-75% of total volume of concrete (normal/ordinary concrete) 90% of asphalt pavements.
• Aggregates make up 60-75% of total volume of concrete (normal/ordinary concrete) 90% of asphalt pavements.
• Aggregates - Sand, gravel, boulders, stones or rocks that can be crushed into particles.
• Aggregates - By-product or waste materialfrom industrial process ormining operation.
• AGGREGATE SOURCES

  Natural Aggregate

  Contrived Aggregate
• Aggregate Sources - Natural Aggregate

  Sand and Gravel Mine (Pit)

  Quarry
• Aggregate Sources - Contrived Aggregate

  Recycle
• Sand and Gravel Mine (Pit) - Aggregates that come from unconsolidated sand and gravel deposits.
• Sand and Gravel Mine (Pit) - Typically deposited by streams (alluvium) or glaciers.
• Quarry - Aggregates that come from bedrock deposits. Bedrock, which is a consolidated rock includes: granite, basalt, quartzite, gabbro, etc.
• Recycle - Products that include crushed concrete, bituminous or demolition debris and in some instances taconite tailings.
• METHODS OF EXTRACTION AND PROCESSING

  • Underwater Sources

  1. Dragline Excavation
  2. Dredging

  • Land Sources

  1. Track Drills
  2. Blasting Bedrock
  3. Crushers and Screens
• Dragline Excavation

  
• This is Dredging

  
• Track Drills

  
• Blasting Bedrock

  
• Crushers and Screens

  
• CLASSIFICATION OF AGGREGATE - BASED ON SHAPE

  • Rounded aggregates

  • Irregular or partly rounded aggregates

  • Angular aggregates

  • Flaky aggregates

  • Elongated aggregate

  • Flaky and elongated aggregates
• Rounded aggregates are completely shaped by attrition and available in the form of seashore gravel.
• Rounded aggregates result the minimum percentage of voids (32-33%) hence gives more workability.
• Rounded aggregates result the minimum percentage of voids (32-33%) hence gives more workability
• ROUNDED AGGREGATES - They require lesser amount of water-cement ratio.
• ROUNDED AGGREGATES - They are not considered for high strength concrete because of poor interlocking behavior and weak bond strength.
• ROUNDED AGGREGATES

  
• ELONGATED AGGREGATES - When the length of aggregate is larger than the other two dimensions.
• ELONGATED AGGREGATES - The length of aggregate is greater than 180% of its mean dimension.
• ELONGATED AGGREGATES

  
• ELONGATED AGGREGATES - The length of aggregate is greater than 180% of its mean dimension
• FLAKY AGGREGATES - When the aggregate thickness is small when compared with width and length of that aggregate.
• FLAKY AGGREGATES - When the least dimension of aggregate is less than the 60% of its mean dimension.
• FLAKY AGGREGATES - When the least dimension of aggregate is less than the 60% of its mean dimension.
• Irregular Aggregates also known as partly rounded aggregates
• IRREGULAR AGGREGATES - are partly shaped by attrition and these are available in the form of pit sands and gravel.
• Irregular aggregates may result 35-37% of voids.
• Irregular aggregates may result 35-37% of voids.
• IRREGULAR AGGREGATES - These will give lesser workability when compared to rounded aggregates.
• IRREGULAR AGGREGATES - The bond strength is slightly higher than rounded aggregates but not as required for high strength concrete.
• IRREGULAR AGGREGATES