Concrete An Overview
Concrete should be made in such a way that

  1. It has the required workability to enable easier transportation, placement, compaction and finishing
  2. It must have the required compressive strength
  3. It must be durable enough to withstand attack from the external environment
To achieve the above, one must ensure the following

  1. Quality of ingredients
    1. Cement : It should be stored in such a way that it does not absorb moisture
    2. Coarse Aggregates : The size should exceed 4.75 mm and should be strong, hard, clean, durable and graded as per IS:383
    3. Fine Aggregates : The size should be less than 4.75 mm and free of silt and properly graded as per IS:383
    4. Water : It should be clean, fresh and potable. Sea water must not be used as it accelerates corrosion and thereby reducing durability.
    5. Chemical Admixtures : These must be added to the concrete mix to alter properties like setting and hardening and must not exceed recommended limits.
  2. States of concrete
    1. Plastic State : When the concrete is first mixed, it is soft and can be moulded easily, which enables easy placing and compaction. Workability and cohesiveness are the two important properties of concrete in this state.
    2. Setting : This takes place after placing and compaction and during finishing.
    3. Hardening : This happens after setting when concrete starts gaining strength.




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