Mixing Concrete and Mortar

Different jobs require different mixes and a selection of mixes with the proper ratio of ingredients. Depending on the job, you may need to include additional materials to give the mix a specific characteristic. These materials are lime, plasticizer, cement pigment, water proofer and frost proofer.

Mixing by hand on a spot board or plastic tarp:

• Position the spot board or tarp on the ground not too far from the work site.

• Use a shovel to heap the ingredients onto the spot board or tarp in the ratio required for the mix as indicated below. 

• Keep turning the heaped ingredients over with a shovel to mix them thoroughly.

• When the ingredients are well mixed, hollow out the centre of the pile.

• Pour enough water into the hollowed out centre to produce the correct consistency. The amount of water you add can depend on the materials you are mixing. For example, if the sand is wet from being stored outside, you will not need as much water as when the sand is dry. It is best to add the water gradually to avoid pouring in too much and making the mix too wet.

• Carefully push the sides of the pile into the centre with the shovel and begin turning the mix over until you have the correct consistency

Concrete and mortar mix formulas:

The following mixes give the ratio of cement, lime, sand and coarse aggregate (stone) for different types of concrete and mortar mixes. The proportion indicates the ratio by volume, usually a shovel-load. However, if greater accuracy is required in the mixing to maintain the strength or color throughout then it is best to use a bucket to measure out the quantities. In some of the mixes below we have included lime, but you can replace this with a plasticizer if you prefer. 

General-purpose mortar for laying bricks, blocks and pointing:

• 1 cement

• 1 lime

• 5 builder's sand

• Mix with water to produce a consistency that allows the mortar to stick to a trowel when turned upside down

For laying paving stones and patio slabs:

• 1 cement

• 4 washed sand

• Mix with water to produce a consistency that is stiffer than the general-purpose mortar above.

Concrete for foundations:

• 1 cement

• 2.5 washed sand

• 3.5 coarse aggregate

• Mix with water to produce a consistency that pours easily

General purpose concrete for a floor slabs:

• 1 cement

• 2 washed sand

• 3 coarse aggregate

• Mix to a loose consistency

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