Basic information on concrete by Les Kenny
What is concrete?
Concrete is a mixture of cement, sand, gravel and water. More info »
What is cement?
Cement is a powdery type substance made from a mixture of earths materials such as limestone and shale, which is sintered (cause to become solid mass by heating without melting), ground, and mixed with small amounts of calcium sulphate and calcium carbonate.
Cement is activated by water and when mixed with sand and gravel, forms concrete.
Cement is usually grey in color, but white cement can be obtained but is usually more expensive than grey cement. More info »
How to mix concrete
Small amounts of concrete can be easily mixed in a wheelbarrow with a spade but larger amounts might require a concrete mixer.
Towable concrete mixers, both electrical and mechanical (petrol) can be hired from hire plant depots.
Mix in the wheelbarrow or concrete mixer, cement, gravel, sand and water.
For general purpose concrete the mix can be 1 part cement, 2 parts sand and 3 parts gravel.
Most cement bags will have mixture recommendations written on the bags.
How to mix concrete in a wheelbarrow
Small amounts of concrete can be mixed easily in a wheelbarrow with a spade or small shovel.
You can make your own concrete mix using 1 part cement, 2 parts sand and 3 parts gravel.
So, to three-quarter-fill the average heavy-duty wheelbarrow, put in 6 spades full of gravel, 4 spades full of sand and 2 spades full of cement. Mix it all together before adding water.
Next add water, approx half a standard household bucket more or less. Add a little of the water at a time. Mix with the spade from underneath and fold over. Keep doing this and adding the water until it is a uniform consistency.
When mixing, a smaller spade is easier to work with than a larger spade. More info »
How clean should the water be?
Rule of thumb. If the water is good enough to drink, then it is good enough to be used for making concrete.
How to make a concrete slab
A step-by-step example of how to make a concrete slab floor for a 1800mm x 1800mm (6ft x 6ft) garden shed. More info »