Using Bagged Dry Mix Concrete
How do I estimate the quantity I need?
Simply multiply the length by width by depth of the whole of the formed area to be filled and add 10% extra for wastage. This figure will give the volume in m required. (Refer to Ordering Pre-Mixed Concrete for details.)
How many bags of Dry Mix concrete will I need to order?
Dry Mix concrete bags generally carry printed advice on the concrete volume that can be produced from the contents of the bag. By dividing this into the estimated volume (m) required, the number of bags needed to suit the particular project can be determined. See Table 1. (next page)
When mixing concrete at home, it is best to use a portable power-driven mixer which can be hired from plant-hire suppliers.
However, for small quantities of concrete, mixing can be done by hand either on a clean flat surface or in a wheelbarrow (see Making Good Concrete available from the Cement and Concrete Association of Australia).
Insert Table 1 Guide for Quantities of Dry Mix
How do I mix bagged Dry Mix Concrete?
First, check printed advice on the bag to determine how much water should be used. Do not exceed the recommended water content as this will reduce
the final strength of the concrete.
When using a concrete mixer Check the recommended capacity of the mixer to determine how much concrete can be produced at once. Too
much concrete in the mixer means that batches may not be mixed properly.
Place contents of Dry Mix, preferably in multiples of 1 bag, in mixer and slowly add water to obtain a workable mix up to the recommended water
When mixing in a wheelbarrow, place contents of one bag of Dry Mix in wheelbarrow. You may use a shovel or a spade to mix the concrete; however, a mattock works just as well and is a lot easier on the back. Slowly add up to the recommended water content until you achieve a workable mix.
When mixing on a clean level surface, a typical material used as a level mixing surface is a sheet of solid plyboard.
Place contents of one bag of Dry Mix onto the mixing surface. Thoroughly mix the dry ingredients using a shovel or spade then make a crater in the centre.
Slowly add up to the recommended water content, pouring it into the crater made to trap the water. Mix from the centre, working all the material together until a workable mix is obtained.
When mixing, don't allow water, cement and sand to flow away from the mixed ingredients in the form of a slurry as this may upset the appropriate blend of materials and affect the quality of the hardened concrete.