What are the requirements of mix proportion design of concrete mixing plant

What are the requirements of mix proportion design of concrete mixing station
1, to meet the design of concrete strength grade.
2, meet the construction requirements of the concrete's workability.
3, to meet the requirements of concrete durability.
4, meet lower cement and concrete cost savings under the above conditions.
On the surface, concrete mixing station calculation of small concrete batching plant cement, sand, gravel, the quantity of water is composed of these four materials.
Bona commercial concrete mixing batch plant professionals tell you is essentially based on the production technology of component materials to determine three parameters to meet the four basic requirements: the rate of cement, water and sand flats.