Concrete brick and block making machines come in many sizes. They range from simple manual machines that make 100 blocks or bricks per day to large, fully-automated machines in commercial blockyards that make thousands of blocks or bricks per day. All the machines, whether small or large, work on the same basic principles.
How Machine Works
A concrete brick or block is made of concrete that’s been molded into the correct shape, then allowed to harden and cure. Concrete brick and block making machines consist of a steel framework that holds the other components in place. There’s a chute or hopper for pouring the wet cement, a frame that holds the metal concrete-block molds, a tamper for compacting the concrete in the molds and a mechanism for transferring the molded blocks out of the machine for drying and curing. The machine is set up with the molds appropriate to the blocks or bricks to be made. Manual machines typically mold two or four bricks or blocks at a time, while electric, pneumatic or hydraulic block machines make eight to 16 bricks or blocks at a time, depending on brick or block type.
The ratio of Portland cement, sand and crushed stone in the concrete varies depending on the type of brick or block being made. In general, concrete for molding into brick or block has fine particles of sand and stone and low water content, about half the volume of water used for other types of construction concrete. After mixing, the wet cement mix is poured into the brick or block molds, then pressed down with a compacting tamper driven by gravity in manual machines or by a hydraulic or pneumatic ram in powered machines. More concrete is added and compacted again. Powered machines vibrate the concrete mix while it is being compacted. This process continues until the compacting head can’t press any more cement into the mold.
When compaction is done, the bricks or blocks are freed from the mold and the finished units are slid onto a steel rack, concrete floor or wooden pallet. In small blockyards, the fresh blocks are allowed to sit for a day under cover to fully harden before they are moved outside for curing. In large commercial block yards, fresh block goes onto special racks to be hardened in a steam kiln. After hardening, concrete bricks or blocks are allowed to cure for one to two weeks to develop full strength before being used for building.
The most common machine-made concrete block is rectangular, 8 inches tall, 8 inches wide and 16 inches long, with a double hollow core. The most common solid concrete brick made on block machines is a rectangle 8 inches wide, 16 inches long and either 2 inches or 4 inches high. Block machine makers also offer molds to make half-sized blocks and special blocks for paving, lintels, corners, pilasters, columns, chimneys and other special uses.
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