Concrete Blocks: Types, Uses, Manufacturing, Storage, and Handling

Concrete Blocks: Types, Uses,
Manufacturing, Storage & Handling
A Concrete Block or Concrete Masonry Unit (CMU) is a
standard-size rectangular block used in building construction.
Concrete blocks are some of the most versatile building products
available because of the wide variety of appearances that can be
achieved using them.
What are the Concrete blocks?
These are usually made in huge sizes to make blockwork quicker
and consume less cement in joints than brickwork. If the level of

the voids is over 25%, then they are hollow blocks, and blocks
with voids under 25% are only perforated blocks. The cellular
concrete blocks are for the most part alluded to as lightweight
aerated concrete blocks. All these blocks are extensively used for
partition walls and non-loadbearing walls. Hollow blocks are
specially designed for load-bearing walls, which help in reducing
dead loads of masonry in buildings. Blocks can also be
manufactured with cement and sand and are called cement-sand
blocks or with cement and soil called soil-cement blocks which
have low strength and are used for budget construction.
Concrete blocks entered the building scene in the late 19th
century with a whirlwind of various patents for block designs and
production. After Harmon Palmer invented the first commercially
successful concrete block machine in 1900, the industry
expanded quickly with different makers delivering the blocks with
their stone-like surface created through either a mould or the use
of special aggregates in the concrete mix. Although stonelike
concrete blocks were popular for the first quarter of the 20th
century, they fell out of fashion following World War II.

What are the different types of Concrete Blocks?
1. Autoclave Aerated Concrete (AAC) Blocks - AAC blocks
are precast, foam concrete, sustainable construction
material made from aggregates of quartz sand, calcined
gypsum, lime, Portland cement, water and aluminium
powder. In the wake of blending and moulding, the concrete
is autoclaved under heat and strain and it consequently
gains its particular properties. AAC blocks are sought after,
inferable from their high strength, load-bearing and warm
protection properties. AAC block is utilized as a construction
material for interior and exterior structures. The blocks might

be covered with a plaster finish or with siding materials like
facade bricks or vinyl siding. AAC blocks are generally
utilized in the development of residential chains and different
sorts of private properties, industrial and business structures,
like hotels, workplaces, emergency clinics and schools. As a
result of their phenomenal heat insulation capacity, AAC
bricks find their use in interior and exterior construction
projects. They are ideal for high-rise structures.

2. Hollow Concrete Blocks - Hollow blocks, which have holes
taking up more than one-quarter, (and usually more than half) of
their cross-sectional area, are used in building boundary fences
and other large structures. The holes make them lighter in weight
and can be used to run wiring or piping through them. One can
also run rebar through the holes for greater stability. Hollow
concrete blocks are available in three grades:
● Grade A has a minimum density of 1,500 kg/m3.
● Grade B has a density of less than 1,500 kg/m3.
● Grade C has a density greater than 1,000 kg/m3.
Grades A and B are used for load-bearing concrete block walls
whereas grade C finds its use for non-load-bearing walls.

3. Solid Concrete Blocks - Fully solid concrete blocks look like
grey bricks but are typically larger. They provide excellent
protection from strong winds. They can also be used for projects
such as garden walls, retaining walls, foundations, steps, and
fireplaces. Solid concrete blocks are usually heavier than hollow
blocks and at the same time be cost-effective as well.

4. Fly Ash Blocks - Fly ash Block (FAB) is a building material,
specifically masonry units, containing class C or class F fly ash
and water. Compressed at 28 MPa and cured for 24 hours in a 66
°C steam shower, then hardened with an air-entrainment agent,
the bricks are profoundly durable as compared to traditional clay
bricks. Attributing to the high concentration of calcium oxide in
class C fly ash, the brick is portrayed as "self-cementing". The
manufacturing method saves energy, reduces mercury pollution in

the environment, and often costs 20% less than traditional clay
brick manufacturing.
Differences Between AAC Blocks & Fly Ash Blocks

Differences Between Solid Blocks & Hollow Blocks
Laboratory Testing of Concrete Blocks
Similar to bricks, concrete blocks also need to be tested for their
quality and performance. The IS Code IS 2185: 2008 has all the
different types of tests that can be conducted on different types of
concrete blocks. Below are the most common tests conducted on
concrete blocks
1. Dimension Test - All blocks should be checked in this step.
The length, width and height are measured with a steel

scale. If it is a hollow block, then the web thickness and face
shell are measured with a calliper ruler. A report of the
average length, width and height of the block and average
minimum face shell and minimum web thickness using
recorded dimensions should be prepared and confirmed with
the claimed dimensions.
2. Density Test – In this test, 3 blocks shall be taken to conduct
this test. To determine the density of the block, first, heat the block
in the oven to 100 degrees Celsius and then cooled it to room
temperature. Now take the dimensions of the block and from that
find out the volume and weigh the block. The density of the block

is determined from the below relation and the average density of
3 blocks will be the final block density. Density of block =
mass/volume (kg/m3)
3. Compressive Strength Test - Eight blocks are taken to
determine the average compressive strength of concrete masonry
blocks. The blocks should be tested within 3days after being
collected in the lab. The age of each block shall be 28 days. The
blocks are then placed in a compressive strength testing machine.
After the blocks are placed in the testing machine, one-half of the
expected maximum load is applied at a constant rate, and the
remaining load is applied in not less than 2 minutes. The load at
which the masonry unit fails and the maximum load divided by the
cross-sectional area of the unit will give the compressive strength
of the block. Similarly, testing of the remaining 7 blocks is
conducted and the average of 8 blocks strength is the final
compressive strength of the concrete block.

What are different Field Tests of concrete blocks?
As for small sites or for cases where blocks cannot be sent to a
laboratory for testing, some on-site tests on concrete blocks can
be done to check the quality and performance of the blocks. The
most common tests of these blocks are mentioned below. It
should be noted that these tests don’t require skilled labour so
they can be done by anyone.
1. Drop Test – A block from a batch is chosen randomly and
lifted to one’s chest level, about 4 -4.5 feet from the ground
and dropped on a hard ground surface. It can be done either

vertically or horizontally along the length of the block. If the
sample block breaks into pieces or develops cracks, then it
should either be considered a low-quality block or can be
rejected altogether.
2. Corner Test – The corner of a block sample should be
pressed with one’s thumbnail on all eight sides one by one. If
some particles are broken down from the edge, then these
blocks can be classified as of low quality.

3. Chisel Test – A groove is cut into the solid concrete blocks,
horizontally running on all four sides of equal depth by using
chisels. It should be cut at the centre of the block until the block
separates into two pieces. actions. If the process of chiselling is
hard and takes a significant amount of time, then it can be
considered that the blocks are of good quality. If the depth of the
groove while the separation of the block is more, then the block is
of good quality. While chiselling, if the block breaks into several
pieces, then that block should be avoided as it is of poor quality.
4. Nail Test – In this test, one needs to hammer a nail into the
block sample on different faces of the block. If the block resists
itself by the insertion of the nail and is harder to hammer the nail,
then the block exhibits high resistance.
5. Texture - The blocks should have a grainy surface texture. If
the concrete block has a smooth texture finish, then it indicates
more quarry dust content in its mix proportion. This weakens the
concrete strength which results in a block production of low
compressive strength.

6. Shape & Size – The block should have a uniform shape with
sharp edges. The tolerance of dimensions on either side should
be ±3mm.

How is the Storage and Handling of blocks done?
Blocks are accessible as hollow and solid concrete blocks, hollow
and solid lightweight concrete blocks, autoclave aerated concrete
blocks, concrete stone masonry blocks and soil-based blocks.
Blocks should be unloaded one at a time and stacked in regular
tiers to limit breakage and defacement. They shall not be dumped
at the site. The stature of the stack will not be more than 1.2 m,
the length of the stack being not more than 3.0 m, as far as
possible and the width shall be two or three blocks. Blocks cured
for 28 days only should be received at the site. If the curing period
is less than 28 days, they shall be stacked separately. All blocks
ought to be water-cured for 10 to 14 days and air-cured for

another 15 days; therefore no blocks with less than 28 days of
curing shall be used in building construction. Blocks shall be
placed near the site of work so that minimum effort is required for
their transportation. The date of manufacture of the blocks shall
be suitably marked on the stacks of blocks manufactured at the
factory or site.
Some of the brand manufacturers for AAC blocks in India?
1. Aerocon Blocks - Aerocon bricks are regarded as a premier
building material in India, providing numerous innovative
benefits to construction firms. The manufacturer conforms to

IS 2185 Part-3 standards while developing good quality
blocks in technically advanced facilities across Chennai,
Golan, Jhajjar and Hyderabad. The AAC blocks are
manufactured using fly ash, cement, lime & an aeration
agent, to ensure top-notch quality.
2. Siporex Blocks - Siporex AAC blocks are lightweight,
pre-cast building materials that are used widely in
applications requiring high heat resistance and thermal
insulation. They have been broadly utilised across
skyscrapers across the country, inferable to their high
thermal insulation and heat resistance. A Siporex block is
designed to be lightweight while providing superior sound
resistance for all structures.
3. JK Lakshmi AAC Blocks - JK Lakshmi is one of India’s
leading cement brands, having a wide distribution network
across the country. The JK Lakshmi AAC blocks have been
enormously used across quintessential architectural
landmarks globally, owing to their superior compressive
strength, durability, and on-site workability. The AAC blocks
manufacturer centres around upgrading product quality and
durability, through global advances and conventions. The JK
Smartblox AAC product is developed using advanced

German technology through innovative ‘Green Separation’
and ‘Horizontal Autoclaving’ processes.
Some of the brand manufacturers for Fly Ash Blocks in
India?
1. ACC Fly Ash Blocks - Manufactured as per IS
16720:2018, ACC India Limited has “ACC Green Cement
Bricks” under its “Green Building Centre” initiative that claims
to be saving 15-20% of the cost of wall construction. It has
an excellent wall finish that is achieved by preventing
seepage and efflorescence and has up to 20% of better
thermal insulation as compared to traditional clay bricks.
They are available in all standard brick sizes, i.e. Standard
(190 x 90 x 90mm), Nominal (230 x 110 x 75mm) as well as
a 250 x 125 x 75mm configuration.
2. KJS Fly Ash Bricks - These concrete blocks are sturdy in
build and are extremely appreciated in the markets due to
their environment-friendly nature and are manufactured from
natural raw materials. These are not only resistant to fire but
do not emit any toxic gas when exposed to fire. Available in

even sizes these help in creating even and polished walls
with minimum plastering. The brand claims to have best in
class compression strength and water absorption and since
the sizes of their bricks are 24 – 40% more than the
competitors, it also reduces the amount of Plastering hence,
improving overall project efficiency.
Conclusion:
Concrete Blocks are broadly used in building construction all
through the country. Its properties such as Durability, Strength &
Structural Stability, Fire Resistance, Insulation and Sound
Absorption make it reasonable for different kinds of uses.
Concrete Blocks are appropriate in regions where brick or stone
of satisfactory quality for masonry is not accessible at an effective
cost. If the proper variety of aggregates is available for
manufacturing, they are used for masonry units for Blocks that
can be used for load-bearing or even non-load-bearing walls,
partitions and panel walls.