Jul 302013

A Table for Concrete Mixes by Weight in Kilograms,

by Bag, and by Cubic Meter, for Various Strengths

A batch of concrete mixed on site, moved by wheelbarrow, to the foundation floor.

A batch of concrete mixed on site and and moved by wheelbarrow and placed on the foundation floor area.

We have had numerous requests for concrete mix ratios by weight, by volume, and by mass. Here is a table that was released by the Cement and Concrete Institute for trial concrete mixes from 10MPa to 40MPa. These are trial mixes and should be used to test your concrete before it is used in any construction work. Your “competent person” or project manager should always assess and approve any concrete work undertaken on your site.

The mix proportions in the table are by mass and volume, using different size stone, for different strengths of concrete. You must add water to the mixture until it becomes workable; you can judge this by eye. The difference between various cements and aggregates is not taken into account with these mixes. Make sure that the water is kept together with the mix and is not allowed to drain/run away as this could result in a weaker mix.


These proportions are based on the assumption that a CEM type cement of strength class 32,5 will be used. Cement of strength class 42,5 or higher will give a stronger concrete but may be less economical. Cements with high extender contents (eg CEM 11/B or CEM 11) will develop strength more slowly and will require particular care with curing. Masonry cements complying with SABS ENV 413-1 should only be used with specialist advice.

The amount of water required is not given in the table. The mix should contain enough water to achieve the required consistence. Consistence may be assessed by eye or measured by carrying out a slump test (SABS Method 862-1: 1994)

A mix made according to this table, and to the required consistence, should be assessed for workability and stone content before being used on a large scale.

Quantities of materials per cubic metre of concrete are net. Allow for wastage when ordering – for instance 3% on cement and 10% on aggregates.

A standard bag of cement weighs 50kg so the equivalent quantities and weights are:

1 Bag cement = 50kg = 0.2 m(cubic metre)


Below is the nominal mix proportions (also referred to as the ratios of mixes) for different strength categories, using a 19mm stone.

Concrete Mix Ratios

NB. Low would be average 15MPa, medium 25MPa and high 35MPa. This is a guide only and quantities must be adjusted for the final requirements and specified by a “competent person“.

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  1. […] Trenches in sloping ground can be stepped with a minimum of 400mm overlap. Sloped trenches must not exceed 1:10 gradient. The minimum depth of the strip foundation trench must be at least 400mm below the original ground level. The average minimum thickness of the foundation must be at least 200mm. The strength of the concrete used for unreinforced strip footing must be at least 15MPa or better. For a double storey building reinforced foundations would require 25–30MPa. Trench sides and must be as near to vertical as possible. Trim the sides of the excavation to avoid holes being filled with concrete on the side faces. This wii require more concrete than estimated and will be a waste. When you have finished the excavation measure the actual depth, width and length of the trench, and calculate the actual volume of concrete that you will need. Always add an additional 10% to allow for wastage and unforeseen circumstances. See our tables here: Concrete mixes by weight & volume […]

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