Learn about the different types of concrete, mortar and aggregates and how to choose the right materials for your project.
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Aggregates and cement are mixed together to make mortar or concrete. Mortar is used as an adhesive that can hold bricks and blocks together, or hold paving slabs in place. It can also be used as an exterior finish. Concrete, which contains coarse aggregates, is used for foundations and hard landscaping. Different kinds of mortar and concrete, suitable for various uses, can be achieved by varying the proportions of the ingredients. Aggregates and sands can be bought in bags, in bulk or in ready-mixed bags.
How much do you need?
Seek advice from your supplier on how much of each constituent you need for your project. To give you a rough idea, to lay 100 bricks with general-purpose mortar you would need: 55 pounds of cement, 220 pounds of sand and 22 pounds of lime. In practice, this is one bag of cement, four bags of sand and half a bag of lime. The table opposite gives the proportions needed for a variety of mixes.
The adhesive in a mortar mix, cement binds together the components and dries to a stable, hard finish. It must be stored in a dry atmosphere and is unusable if it gets damp.
Portland: Gray in color; the most commonly used cement.
White Portland: A lighter version of Portland cement.
Fast-set: Sets very quickly, so is ideal for small DIY tasks.
Sulfate-resistant (Type II Portland cement): For cement in contact with a clay-rich soil, or soil that is high in sulfates.
Expansive: Hydraulic cement that expands during the hardening process.
These are quicker to use, but are more expensive.
Mortar mix: A general-purpose mortar.
Slab mix: For laying paving.
Concrete mix: A general-purpose concrete.
Pour the appropriate portion of a premixed bag of ready-to-mix concrete into a tub (Image 1).
Add the minimum amount of water recommended. The less water used, the stronger the dried, finished product will be (Image 2).
Use a garden hoe to mix the concrete. This way, you will reduce the strain on our back (Image 3).
Mix the concrete, adding water if needed, until the mixture is the consistency of soft peanut butter (Image 4).
Excerpted from Do It Yourself Home Improvement
© Dorling Kindersley Limited 2009