Basics of Concrete

Concrete Mix Ratios - Cement : Fine Aggregate : Coarse Aggregate

• M10 =1:3:6
  
• M15= 1:2:4
  
• M20 = 1:1.5:3
  
• M25 = 1:1:2

The numbering denotes strength of the concrete. The higher the number the higher the strength.
For M30 and above, only design mixes are used.

Notes:

• These mixes are based on OPC 43 cement. If OPC 53 or any other grade of cement were to be used then these ratios would change.
  
  
• M10 means that the concrete mix should have a compressive strength of 10N/mm2 and so on
  
  
• These ratios are based on a volumetric mix and not a mix based on weights of the ingredients
  
  
• IS Code 456 deals with the various grades of concrete
  
  
• RMC is Ready Mix Concrete supplied by the RMC plants to the construction site in transit mixer trucks
  
  
• Cost of Ready-Mix-Concrete including transportation is Rs 3000 per cum
  
  
• As the water to cement ratio increases, the strength and durability of concrete decreases. However adequate water to cement ratio must be used for workability of concrete.

Concrete is tested by:

1. Cube Test for strength
2. Slump Test for workability