Concrete blocks are nowadays replacing bricks in masonry construction, notably in many multi-storeyed buildings. They are available in three types namely solid, hollow and cellular, widely used for the construction of filler walls and boundary walls in RC framework.
CONCRETE BLOCKS are usually made in large sizes to make blockwork faster and consume less cement in joints than the brickwork. If the percentage of the voids is more than 25%, then they are hollow blocks and blocks with voids less than 25% are only perforated blocks.
The cellular concrete blocks are generally referred to as lightweight aerated concrete blocks. All these blocks are extensively used for compound walls and non-loadbearing walls.
Hollow blocks are specially made for loadbearing walls, which are useful in reducing a dead load of masonry in buildings. Blocks can also be with cement and sand called cement-sand blocks or with cement and soil called soil-cement blocks which are of low strength and use for low-cost construction.
BIS recommends a fineness modulus of the combined aggregate between 3.6 to 4 and coarse aggregates used are of size 6 to 12 mm. Lean mixes up to 1:8 are generally used. Concrete mix for concrete blocks should not be richer than one part of the cement to six parts of the volume of combined aggregate.
Concrete blocks can be handmade and also machine-made. The cast block is then cured in a water tank or yard for at least 14 days (water need to be changed at least every 4 days).
After curing, the blocks are dried for 4 weeks before being used in masonry construction. They should be stacked with voids in the horizontal direction to facilitate easy drying, or they should be steam cured and dried.
The whole process allows the complete shrinkage of the block to take place they are laid on the wall, which is very important for strong walls.
The main disadvantage of concrete blocks is shrinkage due to the movement of moisture content which is not present in bricks. As these blocks are much larger than bricks, any foundation movement will cause blockwork to crack more than the brickwork. For Source Info, Click here!
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