Clay brick manufacturing process Part two
Screening – dr y processing
Before being shaped, the clay is screened and oversize pieces are returned to the pan mill for further crushing.
Shaping
Bricks are hand formed, pressed or extruded into their final shape. The method used to shape the bricks affects their final appearance and texture, and sets certain limitations on the handling methods employed during manufacture.
Extruded bricks (common method in South Africa)
Clay with an 1825% water content is forced by an auger into a horizontal coneshaped tube that tapers down to the die. Two compaction stages are commonly incorporated, with a vacuum chamber between them to remove any air in the clay that would reduce the strength of the end product.
The extruded clay column is cut into bricksized pieces by an arrangement of wires. Extruded bricks, although often smooth, may be mechanically patterned or textured. Most bricks of this type have anything from 312 perforations, that, by increasing the surface area, reduce the required drying, firing, and cooling times. Any internal stresses are relieved by the perforations and prevent distortion of the bricks during firing.