Influence of Size , Shape, Texture of coarse aggregate on the properties of concrete

Influence of Size , Shape, Texture of coarse aggregate on the properties of concrete:


Size:

  1. Largest maximum size of aggregates result in
    • Reduction of cement content.
    • Reduction of water Requirement
    • Reduction of drying shrinkage.
  2. size of coarse aggregate depends upon the thickness of section, spacing of reinforcement,  clear cover etc.
  3. Larger the size of aggregates, lesser is the surface area of the aggregates that leads to the lesser area for the hydration of cement and also there is a possibility of accumulation of water beneath these larger size aggregates that leads incomplete hydration hence reduces the strength.

Shape and texture:

Shape:

  1. It is important because it effects workability of concrete.
  2. The aggregates are available in different shapes such as rounded aggregates, angular, flaky, irregular, elongated.
  3. Rounded aggregates are of smooth textures hence yield poor concrete, due to lack of bond between the smooth surface of the aggregate and cement paste- good workability and lower water demand.
  4. Angular aggregates are of rough textured hence provides better bond between surfaces of aggregate and cement paste hence results in fair workability but required more water.  
  5. and also the surface area of angular aggregates is more than smooth rounded aggregates. hence results in higher bond strength than rounded aggregates.
  6. hence angular aggregates require more water that results in less strength than round aggregates.
  7. Flaky aggregates affects the durability of concrete because they tend to be oriented in one plan with bleeding water and air voids beneath. and also elongated aggregates are similar to flaky. 

Texture:

  1. Surface texture of the aggregates affect its bond to the cement and also influence water demand of mix.
  2. rough textured aggregates develops higher bond strength in tension than smooth textured aggregates.
  3. the shape and surface texture of aggregates hence influence strength of concrete at greater extend.
  4. flextural strength is more affected than the compressive strength.

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