For manufacturing concrete blocks, basic material required i.e.

·        Cement

·        Sand

·        Shingle (coarse sand) metal

·        Grit

·        Dust etc.


Proportion of material

The following proportions can be used for manufacturing non-load bearing block to get the required strength and about 35 blocks/bag of cement.

1 : 5 : 10

Cement (1 bag) :  Fine Aggregate (3 Sand + 2 Shingle) : Coarse Aggregate (5 Metal + 5 Grit)

A small quantity of stone-dust may be added for denser blocks. Proportions of stone-dust should not exceed 20% of the fine aggregates.


Concrete block manufacturing procedure

The following procedure should be followed for the manufacturing blocks.

  • Concrete block shall be 30 cm x 150 cm x 20 cm or 30 cm x 10 cm x 20 cm.
  • A platform should be prepared by laying P.C.C.
  • The size of the platform should be large enough to mix at least 25 depos (heaps).
  • On this platform, depos of the material should be dumped as per the decided proportions, using farma (weigh batcher).
  • Separate depos should be dumped for each cement bag.
  • Generally, the contractor mixes one depo of 5 to 6 bags of cement at a time leading to improper mixing, ultimately affecting the strength of the block.
  • Mix the cement thoroughly to get a uniform dry mix.
  • Water should then be added in the depo and wet mixing should be done thoroughly.
  • Water-cement ratio should be kept very low, as higher w/c ratio block cannot stand for a long time.
  • Now, compact the concrete.
  • Compaction is important for manufacturing the blocks, since the strength of the block depends on how well the block is compacted.
  • To make the block fully compacted, the moulds should be filled in layers and compaction done by tamping rod or with electrical vibrator.
  • With a hand operated machine 25 strokes are required per layer, while electrical compaction needs 15 seconds to compact the block completely.
  • These blocks are then carried manually to its initial stacking yard for setting.

·        Similarly, hollow blocks can be prepared by making certain changes.



Concrete Block Making Machine


Stacking and Curing of the blocks

The following steps are involved.

  1. Freshly prepared blocks should be kept in a row with a gap of 5 cm or 7 cm gap, for at least 24 hours without any disturbing for the initial setting of the concrete.
  2. After 24 hours, the pallets can be removed from the base of the block by turning the block slowly on its side.
  3. The block should be allowed to lie in this position for another 12 hours before stacking it in the stacking yard. Curing of these blocks should be done at least 15 days, 4 times a day.
  4.  The blocks should then be carried to the stacking yard for stacking and curing.