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Step 1
Concrete blocks are usually produced using a semi-mechanized stationary type machine. These machines run thousands of dollars and allow you to produce a 1000 blocks per day. But if you are just starting out and can't afford a machine yet, you can build your own mold.
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Step 2
Using a concrete block as a template, measure around the outside of the block and cut 2 x 4's to length. You will be making a box. 4 sides and a bottom but no top, as you will be pouring the concrete into the box. The Typical size is 300 x 200 x 150 mm. Use screws to hold the box together instead of nails. When you get the hang of it you will want to build a lot more wooden molds and can produce 100 blocks a day.
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Step 3
The recipe for the concrete block is 1:12-14 in other words 1 part cement : 12-14 parts sum graded aggregates. Aggregate is sand, gravel, crushed stone, slag, and recycled concrete and is used to reinforcement the strength. You will use fine and course aggregate.
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Step 4
Put plastic inside your wooden mold and then pour in the concrete. Wait 24 hours, flip your block out and make another one.
