Mixes are proportioned by combining cement, sand and stone in a volume ratio that is appropriate to a broad strength category. Water is added to the mixture until workability, judged by eye, is satisfactory. This approach ignores differences between specific cements and aggregates.
Proportions for different strengths are shown in the table below. This table gives equal amounts of sand and stone. Such proportions work reasonably well with crushed stone. Proportions with twice as much stone as sand, e.g. 1:2:4, make harsh stony concrete and should not be used for South African materials.
Nominal mix proportions for different strengths, using 19-mm stone
|Nominal Proportions||Batch based on 1 bag cement, 50 kg||Concrete strength category|
|Proportions||Approx. yield, l|
|Common cement||Sand in the loose moist state||Stone|
|1:4:4||1 bag||130 l||130 l||190||Low, e.g. house foundations|
|1:3:3||1 bag||100 l||100 l||150||Medium, e.g. domestic driveways and floors on ground|
|1:2:2||1 bag||65 l||65 l||105||High, e.g. workshop floor|
Note: A standard wheelbarrow for concrete that complies with SANS 795 (type 2) has a capacity of between 60 and 70 litres.
Source: Cement and Concrete Institute