Concrete blocks, sometimes called sandcrete blocks, are made
from a mixture of hard, durable and clean sand, cement and water. On setting
and hardening, the blocks attain sufficient strength to be used as walling
units.
TYPES OF BLOCKS
There are two main types of blocks which are the light-weight
and the dense blocks.
The light-weight blocks are made with light-weight aggregates
or with aerated concrete. Lightweight aggregates with which blocks be made
include well burnt clinker, wood sawdust, foamed slag, expanded clay. Most of
these materials are by-products of industrial production, so the blocks are
more popular in nations with greater industrial growth.
The dense blocks are made from dense aggregates. They include
natural sand and crushed rock. Blocks made from such aggregates normally have
densities of 1920 to 2080kg/m3. Dense blocks may be solid or hollow.
Hollow blocks have a relatively small bearing area and exert up to four times
as much pressure on the mortar as lightweight blocks or burnt clay bricks.
CLASSIFICATION OF BLOCKS
There are basically three grades of building blocks. These
are:
v Dense aggregate blocks which are suitable for
general use in load-bearing external walls including works below ground level
damp proof course.
v Lightweight aggregates blocks which are used for
load-bearing internal walls including use below ground level damp proof course
and inner leaf of cavity and composite walls.
v Non-load-bearing lightweights blocks which are used
for non-load –bearing partitions.
Materials used for making building blocks include natural
sand and crushed stones, by-products of industrial production such as clinker,
foamed or air-cooled slag, sintered pulverized fuel ash, saw dust and wood
shavings and expanded clay or shale.
The following are some qualifications of a block, they are:
- A good block must have enough strength in order to carry the weight of the objects in it.
- It must be durable
- It must have thermal insulation
- It must be able to resist fire
- Sound transmission and absorption must also be made available in it.
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