Mixing Concrete

Front Cover of book

Home Maintenance Manual

by Simon James

Published by
Sphere Books Limited in 1983

ISBN 0 7221 0582 7

As the title implies, this is a general DIY book, describing Plumbing, Electrical and Carpentry projects, as well as Bricklaying

How to mix Concrete
Images and text from page 186-187

Mix the sand and aggregate in the correct proportions
Measure out the cement and add this to the heap

Image from page 187

Make a crater in the middle of the heap
and pour in water as required

Image from page 187

Mix well with a spade, turning constantly
until it is all completely wet

Image from page 187

The mix should be stiff enough to hold ridges
made with the edge of the spade

If more water is required, use a watering can
fitted with a rose

Image from page 187

Concrete consists of Cement mixed with Gravel and Sand, called Aggregates, and bound together with water

The gravel, or sometimes crushed stones, is known as a Coarse Aggregate and sand is a Fine Aggregate

Portland cement is used for most concretes, though there are fast-setting cements available which should be used if there is a risk of heavy frost before the cement has had time to harden

Frost is concrete’s worst enemy, it will cause it to disintegrate and so it is advisable not to carry out any concreting work during the winter months, unless absolutely necessary

When buying aggregate, ask for 'all-in' which has the sand and stones already mixed. For small jobs you can buy ready-mixed aggregate and cement, all you need to do is add the water

It is important that only clean, fresh water is used. Rainwater may contain impurities which will affect the setting. The amount of water is also important - too much will produce a weak concrete that will shrink and crack as it sets

The aggregate and cement should be mixed in proportions suitable for the work to be done. For heavy-duty work, such as a driveways, floors or fence posts, use 1 part of cement to 4 parts of all-in aggregate. Paths can be repaired with a mix of 1 part cement to 3 parts aggregate

It is the coarse aggregate that gives concrete, its body and strength, but this is not needed for filling cracks and holes and a mix of 1 part cement to 3 parts of coarse sand is sufficient for this work

When mixing concrete measure out the aggregate first, then add the cement. Try not to make more than is necessary for the job. It is better to make several mixes than to overestimate and have concrete left over

Add water in small amounts until you have a workable mix, with no dry aggregate. For the best results use a watering can fitted with a rose; this will ensure an even spread of water

Concrete made with Portland cement takes about four days to set in warm weather, but it should not be allowed to set too quickly. Cover it with damp sacking or polythene sheets or a layer of damp sand

Boards placed on bricks and laid across a concreted path or driveway will prevent dogs, cats and birds leaving their footprints

For mending cracks in a concrete path or drive, use 1 part cement, 3 part sand and add a PVA bonding agent that will give a good bond between the old and new concrete