Concrete Mix on Site

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).

We also have a 'Imperial' version of this calculator here.

Dimensions

Length in Metres
Width in Metres
Desired compacted depth in mm
Total m3

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

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

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