Feb 152008
 

Every now and then you will find you might need to mix up some concrete. For creating a new slab or patching up an old area, making a small mix is required. How you go about this will depend firstly on the quantity you require, followed by how much effort you want to put in. If you are only doing a very small area, buying a couple of bags of pre-mixed concrete mix is going to be the best option. Just mix with water and away you go. Simple and easy. If it’s a larger area, buying a bulk load of sand and screenings will be cheaper for you.

When mixing concrete, the standard mix is 4 parts screenings, 2 parts sand and 1 part cement.

To make life easier for you, we stock dry concrete mix in bulk. This is a mixture of our 14mm screenings and concrete sand. Simply use 6 parts of this to 1 part of cement. When adding water to you mix, add it slowly. Adding too much water will ruin your mix. Remember, you can always add more water, but you can’t take any out. You want your mix to be ‘sticky’ and not runny.

Concrete mix versus Rapid Set concrete

Rapid set concrete is very convenient to use. Set your post, mix with water in the hole and 15 minutes later the mix is set. The trade off for using rapid set is the strength of the concrete. A standard concrete mix is usually around 25MPa in strength. A rapid set mix is usually around 15MPa in strength. BAAG recommends concrete mix is used instead of Rapid set for any structural jobs. Rapid set is fine for a letterbox or clothes line, but the extra strength of a conventional concrete mix could mean the difference between your wall staying upright and falling over.

Mixing Mortar

Fancy laying some bricks? All you need is bricks and mortar. Mortar is a mixture of brick sand and cement. The standard mix is 6 parts sand to 1 part cement. When adding water, you want to keep the mix ‘doughy’. The mix should sit on your trowel, not run off. Avoid a ‘runny’ or ‘soup’ mix. If too much water is added, the mortar will become far weaker when dry. Pre-mixed Mortar mix bags are available from Landscape Supplies at BAAG. Again, just add water (slowly) and mix.

The use of EcoSYN-Lime / Limil

For many years now Limil has been added to make a mortar mix more workable to the user. It makes the mix dry more slowly and is less liable to crack. A new product has recently been released; EcoSYN-Lime. Replacing a 20kg bag of Lime with a 600g bag of EcoSYN-Lime will seem strange at first, but these small bags of synthetic builders lime will provide a stickier, stronger, flexible and more consistent mortar mix.

You’ll use up to 50% less water in a mix and see a better finish in your work. The tradies who have tried these bags so far have loved the product. A 600g bag costs around the same as a 20kg bag of hydrated lime. We also are stocking larger 2.4kg bags (enough for 16 mixes) for those who do a lot of brickwork.

Reinforcing concrete

Reinforcement is used in concrete to increase its strength and ensure the slab is structurally sound. Steel is the most common thing used. It is best if it is located towards the centre of slab. BAAG stocks sheets of reinforcing mesh, 3- bar trench mesh and rod.

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