Concrete Blocks

Blocks are larger than bricks. For this reason a block usually requires both hands to lift it for laying. However, because they are larger, they can be laid more quickly than bricks, but the bigger size also means less versatility in laying especially when building up ends or corners and also laying to curves.

Generally blocks are intended to be plastered.

A concrete block is one of several precast concrete products used in construction. The term precast refers to the fact that the blocks are formed and hardened before they are brought to the job site. Most concrete blocks have one or more hollow cavities, and their sides may be cast smooth or with a design. In use, concrete blocks are stacked one at a time and held together with fresh concrete mortar to form the desired length and height of the wall.

 Concrete blocks are termed either dense or lightweight. Lightweight concrete blocks can be one-third the weight of dense blocks. Lightweight blocks have the following advantages;

 - easier to handle and quicker to lay,

 - the air in lightweight block provide better sound and thermal insulation,

 - the lighter weight results in lighter foundations and structural members, and

 - they can be cut and chased with hand tools and hold nails and screws without plugs.

Types of  concrete blocks

Solid blocks – no formed holes or  slots.

Cellular blocks – with cavities (holes) which do not pass through.

Hollow blocks – with cavities which pass through.

Hollow Blocks

Solid Block

 Strength

The minimum crushing strength of concrete blocks are given below:

	Concrete density1 kg/mm3	Strength N/mm2
Dense aggregate	1500-2000	2.8-3.5
Lightweight aggregate	700-1500	2.8-10.5
Autoclaved aerated	400-900	2.8-7.0

Thermal and sound insulation

Thermal conductivity of blocks varies with density. Lightweight concrete blocks have better thermal insulation compared to denser blocks.

Fire resistance

Fire resistance of concrete blocks is good.

 Durability

Durability of facory-made blocks is generally good. Blocks made with dense aggregate and having a compressive strength of at least 7 N/mm²  can be used for external walls and below ground level as damp-proof courses.

Ease of construction

The speed for constructing a masonry wall using concrete blocks is faster that usual bricks-made wall. This is because the sizing of blocks is more massive then bricks.T. Furthermore, cinder and concrete blocks typically have much lower water absorption rates than brick. 

Construction of masonry wall using concrete blocks

Before filling in corefill

The various types of concrete blocks that had been appeared in the market now.