Introduction

 

  • For extruded bricks the clay is mixed with 10-15% water (stiff extrusion) or 20-25% water (soft extrusion). This is forced through a die to create a long cable of material of the proper width and depth. This is then cut into bricks of the desired length by a wall of wires. Most structural bricks are made by this method, as it produces hard, dense bricks, and suitable dies can produce holes or other perforations. The introduction of holes reduces the volume of clay needed, and hence the cost. Hollow bricks are lighter and easier to handle, and have thermal properties different from solid bricks. The cut bricks are hardened by drying for 20 to 40 hours at 50 to 150 °C before being fired. The heat for drying is often waste heat from the kiln.
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