1- RAW MATERIALS
The concrete commonly used to make concrete blocks is a mixture of cement, water, sand, and crushed rock. This produces a light grey block with a fine surface texture and a high compressive strength. A typical 8” Hollow concrete block weighs 20kg.
In general, the concrete mixture used for blocks has a higher percentage of sand and a lower percentage of gravel and water than the concrete mixtures used for general construction purposes.
In addition to the basic components, the concrete mixture used to make blocks may also contain various chemicals, called admixtures, to alter curing time, increase compressive strength, or improve workability.
When a production batch starts, the required amounts of sand, gravel, and cement are individually weighed and transferred into a concrete mixer where they are mixed for a set duration. After mixing is completed the concrete is transported to the block machine, which can be by conveyor or travelling skips.
- Once the concrete reaches the block machine it is held in a hopper above the machine ready to be called into the mould below.
- Once the concrete is called into the mould it is compacted to form the shape of the required block/paving stone.
- The compacted blocks are then pushed out of the moulds onto a steel pallet.
- The pallet and blocks are then transported by conveyor to the curing chamber.
- The curing chambers can hold several thousand blocks at one time and are automatically transported into several chambers.
- After a specified curing period the blocks are automatically retrieved from the curing chamber and once again transported by conveyor to an automatic cuber.
- The finished blocks are picked up by a robotic grab and stacked into bigger packs of blocks.
- These are then strapped and moved to the load out area where they are moved to an external stock yard awaiting delivery or direct to waiting vehicles.