Concrete Blocks

Blocks could be solid or hollow. They can be handmade or machine made. The materials needed for their manufacture are cement, aggregate and water. Fly ash or other admixtures are also sometimes used. The concrete mix used for the manufacture of blocks is generally (1 cement to 5 or 6 of combined aggregates) through volume. The fineness modulus of the combined aggregate shall be among 3.6 and 4. The blocks could be compacted in the moulds preferably or manually manufactured in block making machines. The blocks shall be cured for 14 days. Steam curing could be adopted to save time.

The concrete blocks, nominal dimensions are as provided below:

Length: 400, 500 or 600 mm

Width: 50, 75, 100, 150, 200, 250 or 300 mm

Height: 100 or 200 mm

Hollow concrete blocks are manufactured in three grades, as elaborates below:

Grade A

Load bearing units along with a minimum density of 15 kN/m³. The average compressive strength shall be 3.5, 4.5, 5.5 or 7 N/mm². The thickness of the face shell and web should not be less than 25 mm.

Grade B

Load bearing unit with a block density among 10 to 15 kN/m³. The average compressive strength shall be 2, 3 or 5 N/mm².

Grade C

Non-load bearing units with block density among 10 to 15 kN/m³. The average compressive strength shall not be less than 1.5 N/mm².

Solid concrete blocks are made for load bearing units along with a block density of not less than 18 kN/m³. The average compressive strength shall be among 4.0 to 5.0 N/mm².

The water absorption of the concrete blocks should not exceed 10% through weight.