Typical Concrete Mixtures (by Volume)

Ratio of
  Use or Application
1:3:6   Unexposed, normal static loads; no rebar
1:2½:5   Normal exposed foundations and walls
1:2½:4   Basement walls
1:2½:3½   Waterproof basement walls
1:2½:3   Light duty floors, driveways
1:2¼:3   Driveways, sidewalks and steps
1:2:4   Reinforced roads, walls and buildings; lintels
1:2:3½   Retaining walls
1:1¾:4   Light duty floors
1:1:1½   Fence posts