Manufacture of Concrete Masonry Units

The process of manufacturing concrete masonry units begins by mixing stiff concrete composed of Portland cement, aggregates, and water. This mixture is then poured into metal molds. To ensure the concrete settles uniformly and to avoid separation of its components, the mixture in the molds is subjected to vibration. Shortly after, the still-wet blocks are removed from the molds and placed on racks.

These wet blocks are then transported for curing, which can occur in one of two environments: a steam kiln for steam curing or an autoclave for high-pressure steam curing. This step is crucial for the blocks to achieve the necessary hardness and durability.

While the nominal size of a typical block is listed as 8 inches in height and width and 16 inches in length, the actual size is slightly smaller to accommodate the thickness of the mortar joints, which are typically three-eighths of an inch.

Concrete masonry units are categorized into three main types: solid load-bearing, hollow load-bearing, and non-load-bearing. Each type is designed for specific structural requirements and is available in various shapes and sizes to suit different building needs.

For instance, A-blocks are designed for constructing walls that need vertical reinforcement bars. These blocks have hollow cores that are filled with grout, ideal for situations where there is limited space to maneuver the blocks over protruding bars. Furthermore, concrete blocks are classified based on their densities into normal weight or lightweight categories.