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How to make concrete bricks and blocks

Pile of concrete bricks and blocks

Making your own concrete bricks and blocks is easy. It can be done outside with just a few items and will save you money. Small-scale businesses can even be started through the production of concrete bricks.

Concrete bricks and blocks can be solid or hollow, it depends on the builder’s preference. Hollow bricks and blocks are lighter and require less concrete to make. Bricks are smaller than blocks, but both can be made using the same techniques.

Making concrete bricks is quite easy, but they need to have a standard size and consistent quality if they are to be sold for a profit. Whether you want to make concrete bricks to sell or for your own building project, here are a few things to think about.

Choosing a site for making concrete bricks

Before you start constructing your own concrete bricks, make sure you have access to a flat piece of land big enough to store the equipment, materials and finished bricks. There should be enough space to store the aggregates (rocks or gravel and sand) and cement.

Do not store the aggregates or cement on bare ground as soil and water can contaminate the materials. Do not store them under trees as leaves and seeds can fall into the stockpiles. Keep aggregates and cement dry and separate until you need to mix them. Bags of cement should ideally be stored in a dry room.

You’ll need space to produce and store the concrete bricks and blocks. A flat concrete slab is ideal – about 50 square metres is big enough to store 1000 bricks or 200 blocks for curing and drying. This slab can be slightly sloped to ensure that rainwater runs off but not so much that the stockpiles fall over.

Using the right equipment to make concrete bricks

To make your own concrete bricks, you’ll need various general purpose tools and a moulding machine. There are two types of moulding machine – a stationary block moulder that produces one brick at a time on a pallet, and an “egg-layer” machine that moulds bricks on a concrete slab. Both of these moulding machines come in hand-operated versions and electrically-powered versions.

Concrete mixers are not necessary, but they do make the process easier. Mixing concrete by hand will save money but it is more physically challenging. It can be done with a shovel on a flat concrete slab or steel sheet. Never mix concrete directly on the earth as the soil will contaminate the mix.

If you are able to use a concrete mixer, only a pan mixer should be used. Drum mixers do not work because they cannot mix the semi-dry concrete needed to make bricks. Other equipment needed includes wheelbarrows, hosepipes, plastic sheeting and shovels.

Using the right cement and aggregates

The cement used for making concrete bricks should be strength class 42,5N or higher as the concrete needs to cure as quickly as possible. Tembo Cement’s SupaSet and TemboFundi brands are ideal for this purpose.

Sand and stones will form the aggregates for the concrete bricks. You can use fine river or pit sand, coarse sand (up to 5mm in size) or stones with a maximum size on 13mm for solid bricks or 10mm for hollow bricks. Usually, it is possible to make concrete bricks with just coarse sand, but a combination of aggregates can be used.

When making your first batch of bricks, try using coarse sand only. Then replace some with fine river sand and stones to see what makes the strongest mix for your bricks. Try using aggregate to cement ratios of 6:1, 8:1 and 10:1 (230 litres, 300 litres and 380 litres of aggregate per 50kg bag of cement).

For each combination or ratio, mix a batch of concrete with water and use the brick moulding machine to create some test bricks. This will allow you to find the perfect mixture for your needs – the heavier the freshly moulded brick, the better. Test the strength of the dried bricks by knocking them together – a hollow thud means they may be weak, a ringing sound means that they are strong.

Making your own concrete bricks

Once you’ve established the best mixture for the concrete bricks and blocks, you can start producing them in larger quantities. Make sure you have enough cement and aggregates to make the number of bricks you require.

Using an aggregate to cement ratio of 8:1 with three-and-a-half bags of cement and a cubic metre of aggregates will produce enough concrete mixture to make about 400 bricks. This number can vary depending on the size of the bricks and whether they are hollow or solid.

The amount of water added to the concrete mix is usually judged by eye. Once the approximate amount of water needed per batch is known, measure about 90% of this and add it to future batches. The remaining 10% can be added slowly to get the right consistency of concrete.

The concrete mixture must be wet enough to hold together when compacted, but not so wet that the bricks sag and deform when removed from the mould. If you see ripple marks on the bricks once they are moulded, then your mixture has slightly too much water. If the concrete is too dry, the bricks won’t bind properly and will crumble when dried.

To mix the concrete, first spread the sand out on a steel plate or concrete slab. The sand should be 5cm to 10cm thick. Spread the cement over the sand and add any other aggregates. Mix the sand and cement with a shovel until a uniform colour is achieved. Sprinkle water over the surface of the mixture and continue to mix until the right consistency of concrete is achieved.

Place the concrete in the moulding machine and compact it about six to eight times to ensure that the brick is properly formed. Take the moulded brick out of the machine with care and set them somewhere to cure for seven days. The bricks should be protected from rain and direct sunlight while curing.

You can cover the bricks with a plastic sheet to prevent moisture loss. A light spray of water may be necessary if it’s hot and windy. This will allow the bricks to cure properly and avoid drying too quickly. Congratulations, you’ve just made your own concrete bricks or blocks.

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LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges.

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LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in the Mbeya Region at Songwe in Southwest Tanzania.

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At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.

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