How to Mould Concrete Blocks
1. Prepare the Concrete Mix
Use a semi-dry mix, not wet. Typical proportions: 10-15% cement, 75-85% aggregates, 10-15% water. Maximum aggregate size should not exceed one-third of the smallest cavity dimension. For standard blocks, use 10mm or smaller aggregate. A mix that is too wet causes blocks to slump. A mix that is too dry fails to fill mould corners properly.
2. Set Up the Mould and Machine
Mount the mould on the block machine's vibration table. Tighten bolts evenly in a cross pattern. Verify the mould is level using a precision level. Apply release agent to all cavity surfaces. Align the stripper head precisely with the mould cavities. Misalignment damages blocks during ejection.
3. Configure Machine Parameters
Adjust settings based on block type:
Vibration frequency: 2,500-4,500 RPM (higher for pavers and hollow blocks)
Compression pressure: 10-20 MPa (higher for dense blocks)
Cycle time: 10-18 seconds
Hollow blocks require lower compression to protect core pins. Pavers need higher vibration for surface finish.
4. Run the Moulding Cycle
The cycle has four phases: fill, vibrate, compress, eject. Fill time should ensure all cavities receive correct material volume. Vibration continues for 2-5 seconds until concrete is fully compacted. Compression is maintained for 1-2 seconds. After ejection, inspect blocks for voids, cracks, and dimensional accuracy. UNIK moulds maintain ±0.3mm tolerance on critical dimensions.
5. Cure Blocks Properly
Freshly moulded blocks are fragile. Transfer carefully to the curing area. Initial curing: cover with plastic for 24 hours. Moist curing: spray with water for 7-14 days. Ideal conditions: 20-30°C temperature, above 80% humidity. For commercial production, steam curing reduces time to 8-24 hours.