From the experience I got during the process of identifying suitable material for the projects I was working. I have a written this article comparing various types Brick/Block used for making a wall. This article should be only used as a basic guide and not to take final decision as the characteristics vary across the board due to lack of international standardization.

In case of wall masonry following material are most commonly used

a) Clay Bricks

b) Fly Ash Bricks

c) Solid Concrete Blocks

d) Hollow Concrete Blocks

e) AAC Light Weight Blocks

f) CLC Light Weight Blocks

 

We can compare them on following Criteria

 

1)      Material used in manufacturing

a) Clay Bricks: - Clay / Soil, sand, water, organic material is sometimes added.

b)  Fly Ash Bricks: - Cement, fly ash, Sand, Stone dust, water.

c)  Solid Concrete Blocks: - Cement, fly ash (Depending on manufacturer), Sand, Stone dust, stone aggregates, water.

d)  Hollow Concrete Blocks: - Cement, fly ash (Depending on manufacturer), Sand, Stone dust, stone aggregates, water.

e) AAC Light Weight Blocks: - Cement, fine ground silica, lime, aluminum powder, water.

 

f) CLC Light Weight Blocks: - Cement, fly ash, foam and water.

 

 2)      Colour

a) Clay Bricks: - Shades of Red

b) Fly Ash Bricks: - Grey

c) Solid Concrete Blocks: - Grey

 

d) Hollow Concrete Blocks: - Grey

 

e) AAC Light Weight Blocks: - Grey

 

f) CLC Light Weight Blocks: - Grey

 

3)      Density

a) Clay Bricks: - 1800Kg/cum

 

b) Fly Ash Bricks: - 1700kg/cum

 

c) Solid Concrete Blocks: - 2500kg/cum

 

d) Hollow Concrete Blocks: - 1500kg/cum

 

e) AAC Light Weight Blocks: - 700kg/cum

 

f) CLC Light Weight Blocks: - 600 to 1800kg/cum

 

4)      Sizes

a)Clay Bricks: - 230mm X 100 to 150mm X 70mm varies as per local demand. 

b) Fly Ash Bricks: - 230mm X 100 to 150mm X 70mm varies as per local demand.

 

c) Solid Concrete Blocks: - Variety of sizes can be manufactured as needed by modifying mould.

 

d) Hollow Concrete Blocks: - Variety of sizes can be manufactured as needed by modifying mould.

 

e) AAC Light Weight Blocks: - Variety of sizes can be manufactured as needed by modifying cutting.

 

f) CLC Light Weight Blocks: - Variety of sizes can be manufactured as needed by modifying mould.

 

5)      Comparative Thermal Insulation

a) Clay Bricks: - Average

 

b) Fly Ash Bricks: -Average

 

c) Solid Concrete Blocks: - Average

 

d) Hollow Concrete Blocks: - Excellent

 

e) AAC Light Weight Blocks: - Good

 

f) CLC Light Weight Blocks: - Good

 

6)      Noise Insulation

a) Clay Bricks: - Average

 

b) Fly Ash Bricks: - Average

 

c) Solid Concrete Blocks: - Average

 

d) Hollow Concrete Blocks: - Excellent

 

e) AAC Light Weight Blocks: - Good

 

f) CLC Light Weight Blocks: - Good

 

7)      Compressive Strength

a) Clay Bricks: - Average to Good depending on clay (5 to 15 N/sqm)

 

b) Fly Ash Bricks: - Good (6 N/sqm)

 

c) Solid Concrete Blocks: - Excellent (10 to 20 N/sqm)

 

d) Hollow Concrete Blocks: - Good (6 N/sqm)

 

e) AAC Light Weight Blocks: - Poor (4 N/sqm)

 

f) CLC Light Weight Blocks: - Poor (4 N/sqm)

 

8)      Environmental Impact

a) Clay Bricks: - Very negative as it makes use of top soil, leads to the land being not good for agriculture for some time due to loss of top soil. In case it is manufactured from river clay the impact is not much but still manufacturing is energy intensive as energy is required by burning fuel to bake the bricks.

 

b) Fly Ash Bricks: - Balance/Positive as byproduct Fly ash gets utilized, manufacturing is less energy intensive

 

c) Solid Concrete Blocks: - Negative, manufacturing is less energy intensive

 

d) Hollow Concrete Blocks: - Negative, manufacturing is less energy intensive

 

e) AAC Light Weight Blocks: - Comparatively less negative, manufacturing is energy intensive

 

f) CLC Light Weight Blocks: - Comparatively less negative, manufacturing is not energy intensive

 

9)      Usability

a) Clay Bricks: - Those with low strength break easily into required sizes,  and are easy to handle on work. But the stronger ones made from good quality clay are difficult to break like fly ash bricks.

 

b) Fly Ash Bricks: - Difficult to break, not easy to handle due to weight

 

 

c) Solid Concrete Blocks: - Difficult to break, not easy to handle due to weight

 

d) Hollow Concrete Blocks: - Breaking into sizes is very difficult, Easy to handle

 

e) AAC Light Weight Blocks: - Easy to cut in required sizes, Easy to handle

 

f) CLC Light Weight Blocks: - Easy to cut in required sizes, Easy to handle

 

10)   Availability

a) Clay Bricks: - Availability decreasing in urban areas

 

b) Fly Ash Bricks: - Available with less suppliers

 

c) Solid Concrete Blocks: - Easily available

 

d) Hollow Concrete Blocks: - Easily available

 

e) AAC Light Weight Blocks: - Availability increasing with new manufacturers entering market

 

f) CLC Light Weight Blocks: - Availability increasing with new manufacturers entering market

 

11)   Application areas

a) Clay Bricks: - External walls, Partition or Load bearing walls

 

b) Fly Ash Bricks: - External walls, Partition or Load bearing walls

 

c) Solid Concrete Blocks: - External walls, Partition or Load bearing walls

 

d) Hollow Concrete Blocks: - External walls, Partition walls

 

e) AAC Light Weight Blocks: - Partition walls

 

f) CLC Light Weight Blocks: - Partition walls

 

12)   Efflorescence

a) Clay Bricks: - Generally present

 

b) Fly Ash Bricks: - Absent

 

c) Solid Concrete Blocks: - Absent

 

d) Hollow Concrete Blocks: - Absent

 

e) AAC Light Weight Blocks: - Absent

 

f) CLC Light Weight Blocks: - Absent

 

13)  Water Absorption

a) Clay Bricks: - High

 

b) Fly Ash Bricks: - Very low

 

c) Solid Concrete Blocks: - Low

 

d) Hollow Concrete Blocks: - Low

 

e) AAC Light Weight Blocks: - Very high

 

f) CLC Light Weight Blocks: - Very high

 

 

14)  Process of production

a) Clay Bricks: - Clay is softened with water to workable consistency and it is mixed with some organic matter and salts to give it desired properties and removing any stones or other matter. The prepared clay is than filled into mould to produce raw bricks. These bricks shaped by mould are dried up and then fired to produce the final product. These bricks may be treated with additional process for modifying its properties. Sometimes coloring agents are added to get different color for architectural purpose.

 

b) Fly Ash Bricks: - These are produced by mixing Fly ash, hydrated lime, Quarry dust and gypsum into a mixer where water is added in the required proportion for intimate mixing. After mixing, the mixture is shifted to the hydraulic Brick Making machines. The bricks are carried on pallets to the open area where they are dried and water cured for 14 days. The bricks are tested and sorted before dispatch.

 

c) Solid Concrete Blocks: - A mixture of cement, water, sand, and gravel is prepared. This produces a light grey material with a fine surface texture and a high compressive strength. This mixture is than filled in moulds and is compacted by the weight of the upper mold head coming down on the mold cavities. This compaction may be supplemented by air or hydraulic pressure cylinders acting on the mold head. Most block machines also use a short burst of mechanical vibration to further aid compaction. The compacted blocks are pushed down and out of the molds onto a chain conveyor or pallet. These are than cured with water or steam as per the manufacturer.


d)
Hollow Concrete Blocks: - The process for hollow concrete block is similar to that of solid concrete blocks, only the molds for them are different and sometimes gravels are not used as they might block the mold.

 

e) AAC Light Weight Blocks: - The materials are first mixed into slurry and then poured into large molds where the expansion agent reacts with the alkalis in the cement and lime to produce millions of small hydrogen gas bubbles. The mix expands almost 2 times its initial volume. The hydrogen evaporates and the 'cake' sets up and hardens into a stable closed cell matrix which can then be precision wire-cut into blocks or panels. The green aerated concrete is then steam cured in a pressurized autoclave for about 12-14 hours where upon it undergoes a second chemical reaction and transforms into the mineral calcium silicate.

 

f) CLC Light Weight Blocks: - CLC is a process based on making air bubbles in the form of a foam and then mixing the foam into a cement / sand slurry. The slurry is then poured into moulds. The finished product is cured like normal concrete or Steamed Cured with low pressure to achieve early strength. As compared to AAC lightweight products, CLC air bubbles are significantly smaller, stronger, and each bubble is part of a closed cell system

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