Hollow Block Cavity Geometry and Mould Design
Hollow block cavity size, shape and arrangement influence material consumption and production. Learn which details should be defined in the mould drawing.
How Cavity Number and Shape Affect the Block
Hollow concrete blocks with the same external dimensions can be manufactured with different cavity arrangements. The size and position of these cavities determine the volume of concrete remaining in the block and the location of its internal webs.
The number of cavities alone does not establish whether a block is lighter, stronger or provides better insulation. These characteristics need to be assessed together with the complete product geometry, material properties and relevant performance requirements.
Void Percentage and Material Consumption
Void percentage is the total cavity volume divided by the gross volume calculated from the block's external dimensions, multiplied by 100. Where cavities vary in cross-section through the block height, their actual geometry must be included in this calculation.
For blocks with the same external dimensions and concrete density, increasing the cavity volume reduces the amount of concrete in each unit. However, there is no single void percentage suitable for every hollow concrete block. The design must meet the requirements of the intended application.
Face shell and internal web thicknesses must also be considered when defining the cavities. For a separate discussion of these dimensions, see our guide on how to determine hollow block wall thickness.
Concrete Filling, Compaction and Demoulding
Narrow spaces between the mould's core-forming components can make concrete filling and compaction more difficult. The cavity arrangement should therefore be reviewed together with the aggregate characteristics, filling direction and operating conditions of the concrete block machine.
Tapers and transitions on cavity surfaces also need to be considered for vertical demoulding. Where the upper and lower cavity dimensions differ, this difference should be clearly shown in the technical drawing.
Details Required for the Hollow Block Mould Drawing
The product drawing should specify the block's external dimensions and height, together with the number, dimensions and positions of its cavities. Corner transitions, any tapers and the sections at which dimensions are measured should also be identified.
Block Mould prepares the core-forming components and tamper shoes according to the approved product geometry. The mould layout is reviewed against the machine configuration and production board dimensions.
To request a quotation, send your product drawing, required block height, machine brand and exact model, and production board dimensions. For an existing product, clear photographs of the block and its cavities can help clarify details that are not visible in the drawing.
Contact us to discuss your project and request a quotation.