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On-Site Concrete calculator.

Use this calculator to determine how much sand, aggregate (gravel) and cement is required for mixing on site a given area of concrete (1:2:4 ratio).

The calculations will be completed when you leave the last input field. See below for help on concrete.


Dimensions
Length in metres
Width in Metres
Depth in Millimetres
Total m³ 
Materials
   25 Kg bags    40 Kg bags   1 tonne bags
Cement Kg    
Sharp Sand Kg    
Aggregate Kg    
Water litres    
OR
Ballast (all in) tonnes    
m³    
Approximate labour & material costs

These figures are dependant on many factors such as use of concrete, thickness of concrete, location, price of materials etc.


Desirable properties in a concrete mix

  • Ensure the concrete mix is workable which allows correct placement and consolidation
  • Ensure the optimum desired quality of the hardened concrete is met which improves resistance to freezing and thawing, water tightness (low permeability) , wear resistance, and strength.
  • The quality of the concrete is dependant mainly on the water to cement ratio, so water requirements should be minimised to reduce the cement requirement thereby reducing the overall cost.
  • The mix should be a stiff as possible.
  • Use the largest aggregate practicable.
  • Use the optimum ratio of fines to coarse aggregate.
  • A low water to cement ratio is the number one issue that affects concrete quality. Do not add too much water.

Components in concrete

  • Portland Cement - the aggregate and sand is coated by a paste formed from the cement and water. This paste then hardens and binds the fines (sand) and aggregate together
  • Water - this is needed to chemically react with the cement and to make the concrete workable.
  • Aggregate - The fines are sand and gravel or crushed stone is the coarse aggregate (10, 20 & 40mm) in most mixes.

Admixtures in Concrete

  • Accelerators - added to the concrete to reduce overall setting times and gain early strength. Calcium chloride is the lower cost accelerator, however a non-chloride accelerator should be specified if reinforcing has been used, to prevent corrosion of the steel.
  • Retarder - used in hot weather to delay setting. Also used for difficult jobs and specialist finishes. May also act as a water reducer
  • Fly Ash - improves workability, easier to finish and reduces the cement content.
  • Air Entrainment - improves the workability of the concrete as well as the durability.





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