AAC BLOCKS OR RED BRICKS.. WHAT TO USE IN CONSTRUCTION?

When we are started a construction site, first question come in our mind that what to use to construct a wall. AAC blocks or Red clay bricks. So let us understand what are these materials.

From the many decades, We are using red bricks to construct a wall. Even many years ago,we are using this brick to construct a wall foundation. but when the technolgy enters in india. We have too many substitute of building materials. AAC block is a replacement of red clay bricks. But every material has our pros and cons. So, they both are very useful in market. Let we compare these both material below.

AAC Block



1. Raw Material


  • AAC blocks are manufactured from the mixture of fly ash, cement, lime, gypsum and an aeration agent.


  • Red bricks are made from a mixture of clay (alumina), sand, Lime, iron oxide and Magnesia. Natural soil is used for production of Bricks. Hence,It will vary upon the quality of local soil.

2. Uses

AAC blocks

  • AAC Block can be used to construct external as well as internal walls. It will also use to build mass masonry.
  • According to ‘IS 2185(Part3)-1984’ (Specification for Concrete Masonry Units), Autoclaved Aerated Concrete blocks can be used for
1. Load bearing and non-load bearing walls.

2. Partition and panel walls.

3. Inner leaf of cavity walls or as backing to brick masonry.

4. For external load-bearing walls.

5. Panel walls in steel or reinforced concrete frame structure, if protected from weather by rendering or by some other adequate treatment.

Red bricks


  • Red bricks are strong, hard and durable material. Therefore, they are used as a construction material in creating different structures such as Buildings, Bridges, Foundations' Arches and cornices, Pavements, As an Aesthetic and finish surface etc.


  • Bricks are also used as per its different colours, sizes and orientations to get different surface designs. As an aesthetic material bricks can be used as Facing Bricks, Architectural Purposes, exposed practice work etc.

3. Advantages

AAC blocks

  • AAC blocks are very easy to handle and ordinary tools can be used for cutting.
  • AAC blocks are available in large sizes and hence less no. of joints. This ultimately results in faster construction on site and less consumption of either cement-mortar or chemical and also increasing the strength of wall.
  • Earthquake forces are proportional to the weight of building. Due to light weight of AAC blocks, there will be reduction in dead load of the building. Hence AAC blocks are preferred in high seismic zones. Furthermore, less steel will be required in case of RCC structure.
  • AAC blocks are made from an inorganic material which helps to avoid termites, damages or losses.
  • Use of AAC blocks in the multi-storey building can reduce the consumption of steel and concrete. This reduces the dead load on the structure and increase the carpet area.
  • Reduction in dead load on the structure can greatly reduce the size of structural elements which means that it will increase the floor/carpet area.
  • Easy to convey to upper floors.
  • Use of AAC blocks can significantly reduce the construction time of the project. Time-saving is possible due to the large size of blocks and efficient workmanship.
  • AAC blocks require less curing before plaster.
  • AAC block is a good thermal insulator. so it brings our home cool compare to outside in summer and also reduce the electrical bill of a.c unit.
  • One AAC block of size (600 x 200 x 100 mm) is equivalent to 6 bricks. Hence it reduces 50% of joints resulting in saving of mortar up to 48%. In case of 150 mm or thicker block masonry, the mortar saving is even more due to the avoidance of vertical joint.
  • Minimal wastage of AAC blocks.
  • AAC block is environment-friendly and also saves water as less curing is required. Hence it is popularly used as a green product.
  • The initial production cost of AAC blocks may be more; however, as discussed above, it can reduce the consumption of Steel, Cement, Concrete and labour. Therefore, the whole project cost gets decreased.

Red Bricks/Clay Bricks


  • Red bricks are easy to handle and work with it.
  • Raw material is easily and abundantly available. So, it is economical. Red Bricks are low maintenance, permanent, hard and durable building materials.
  • Compressive strength of brick is good enough for ordinary construction requirements.
  • Different orientations and sizes give different surface textures.
  • Demolishing of brick structures is very easy and less time consuming.
  • Red brick does not require costly equipment for manufacturing process and its manufacturing process is also easy to do.


4. Disadvantages

AAC Blocks


  • The production cost per unit for AAC Block is higher.
  • Plaster sometimes does not stick properly because of its smooth surface. AAC block work needs care during production itself, so that surface does not become very smooth.
  • AAC block also requires a protective finish since the material is porous and would deteriorate if left exposed.
  • AAC blocks are bad resistor of vibration so, Cracks occur more compare to red bricks in it.

Red Bricks/Clay Bricks


  • Time consuming construction
  • A red brick absorbs water easily so Efflorescence may occur due to the presence of salt in water.
  • Rough surfaces of bricks may cause moulds growth if it is not properly cleaned.
  • Continuous use of Red bricks in construction will lead to extensive loss of fertile top soil and hence potential agricultural land.
  • Red bricks are heavy in weight. Since the structure needs to withstand greater weight, more steel is required and hence construction cost is more.
  • Big damage to environmental and loss of fertile land due to use of clay soil excavation for manufacturing of bricks.


5. Appearence

AAC Blocks


  • Colour of AAC Block is Grey. AAC block comes in big size.

Red Bricks/Clay Bricks


  • Colour of clay brick is Red. Clay bricks are smaller than AAC blocks.

6. Properties

A. Size Available in Market

AAC Block

  • Available in 400-600×100-200×100-150-230mm. However, it may vary slightly depending on the manufacturer and user.

Red Bricks/Clay Bricks

  • Standard Modular Size of Red Bricks: 190x90x90mm

Standard Non Modular Size: 230x110x70

This size is more popular in India.


B. Allowable Variation in Size
AAC Block


  • According to ‘IS: 2185’ (Specification for Concrete Masonry Units Part 3 Autoclaved Cellular (Aerated) Concrete Blocks), the maximum permitted variation in the length of the AAC block units is ±5 mm and the maximum variation in the height and width of unit is ±3 mm.
  • The AAC Blocks are accurate in size because it is produced by wire cut technology and is a factory product.

Red Bricks/Clay Bricks


  • Red clay bricks show some differences in size. It may be 10 mm vary in size. It also shows bad right angle.

C. Dry Density
AAC Block


  • Dry density of AAC block varies from 500 kg/m3 to 900 kg/m3.
  • The low dry density of AAC blocks reduce the load on the foundation and other structural components in a structure leading to 55% reduction in weight of walls. Because of reduction in self-weight, AAC block construction attracts less earthquake load.

Red Bricks/Clay Bricks


  • Dry density of red clay bricks varies from 1600 kg/m3 to 1900 kg/m3


D. Weight
AAC Block


  • One 600 x 200 x 100 size AAC block weight is 10 kg.

Red Bricks/Clay Bricks





  • One 230 x 100 x 70 size brick weight is 3.5 kg.

  • E. Compressive Strength

    Strength is defined as a capacity to resist force or pressure.

    AAC Block


    • The compressive strength of AAC blocks varies between 3 to 4.5 N/mm2

    Red Bricks/Clay Bricks


    • The compressive strength of clay bricks varies between 3.5 N/mm2  to 3.5 N/mm2. Depending upon the class of brick.


    F. Water Absorption

    AAC Block


    • Water Absorption of AAC block should not be more than 10% of its weight.

    Red Bricks/Clay Bricks


    • Water absorption of brick should not be more than 25% of its weight for class 3 bricks.

    If the brick or block absorb more water than the above specified limit, it causes adverse effects on the strength of brick as well as the durability of the structure.

    G. Fire Resistance

    AAC Block


    • According to ‘Portland Cement Association’, Fire resistance of AAC block is excellent, with 200 mm thick AAC achieving a 4 -hour rating (actual performance exceeds that and resist fire up to up to eight hours).  Also, it is non-combustible material and will not burn or give off toxic fumes.

    Red Bricks/Clay Bricks


    • 9" thick wall can resist fire for up to 2 hours.


    H. Thermal Conductivity
    The amount of heat transfer from a specific material is called its thermal conductivity.


    AAC Block

    • The thermal conductivity of AAC block varies from 0.21- 0.42 W/mk
    • Thermal conductivity of block is lower and hence less heat transfer happens from block.
    • AAC blocks are made up of fly ash and fly ash has a lower thermal conductivity compared to natural clay, which results in more thermal resistant blocks.

    Red Bricks/Clay Bricks


    • The thermal conductivity of Red bricks varies from 6- 1.0 W/mk.
    • The thermal conductivity of the brick is high, and hence heat transfer from brick is more than the AAC block.


    I. Moisture Resistance

    AAC Block

    • Moisture resistance of AAC block is better than the Red Brick.
    • AAC block consists of unconnected micro pores which prevent the capillary transport of moisture over a long distance.

    Red Bricks/Clay Bricks


    • Moisture Resistance of Red Brick is Average.
    • Moisture resistance depends up on water absorption of the brick and proportion of cement mortar.
    • 100/115mm wall will not have adequate moisture resistance. If poor, it will make walls damp & wet.


    J. Sound Insulation/Noise Transmission

    Sound insulation is defined as the capacity to reduce sound transmission by the building elements.
    Sound abortion of a material depends on its density. Denser the material, higher will be the reflection of sound. However, if the material is porous in nature, the density of the material gets reduced and the air gaps acts as insulation
    Sound transmission also depends upon the thickness of the wall.
    AAC Block

    • The AAC block has good sound transmission property due to the presence of air voids.
    • 40-45 db sound is reduced by 200 mm thick wall.
    • That lightweight also gives a high sound reduction for privacy, both from outside noises and from other rooms when used as interior partition walls.
    • As mentioned above, AAC blocks are light in weight and porous in nature they have very good acoustics properties. Thus, AAC blocks always have good sound insulation compared to clay or red bricks.

    Red Bricks/Clay Bricks


    • The brick masonry wall has good sound insulation property due to its dense structure.
    • 150 mm wall reduces the sound by 45db and 50 db by 230 mm wall.


    K. Termite Resistance

    AAC Block


    • AAC blocks are insect resistant, inorganic and solid wall construction material.
    • AAC blocks do not allow spreading of termites and pests and hence increase the life of the wall.

    Red Bricks/Clay Bricks


    • Red bricks are not termite resistant as they are made from clay which is an organic material.


    7. Efficiency
    A. Labour Output
    AAC Block


    • Less labours are required. The speed of work will be double than that of the clay brick work.

    Red Bricks/Clay Bricks


    • More labours are required. The speed of red brick work will be slow as compared to the block work.

    B. Carpet Area

    AAC Block


    • Since AAC Blocks are thin, available carpet area will be more. This is very important where cost of houses is very high.

    Red Bricks/Clay Bricks


    • Due to more thickness of bricks, available carpet area will be less. But not suitable for high rise and load bearing buildings.


    C. Applicability

    AAC Block


    • AAC Blocks are recommended for high-rise buildings because it substantially reduces total dead load of the building.

    Red Bricks/Clay Bricks


    • Red bricks are used for both load-bearing and non-load bearing walls.

    D. Mortar Consumption

    AAC Block


    • Requires less mortar due to flat and even surface & less number of joints.

    Red Bricks/Clay Bricks


    • Requires more mortar due to irregular surface & more number of joints.


    E. Speed of Construction

    AAC Block

    • Speedy construction of wall due to the bigger block size, light in weight and less number of joints.

    Red Bricks/Clay Bricks

    • The speed of construction of the brick masonry wall is slower than the block construction.

    F. Water Usage

    AAC Block


    • Block is cured by steam and block masonry requires less curing. Hence less water and less electricity are required.

    Red Bricks/Clay Bricks


    • Requires more water for curing and hence high amount of electricity bill and labour cost.

    G. Breakage & Utilization 
    AAC Block


    • Negligible breakage almost 100 % utilisation is possible.

    Red Bricks/Clay Bricks


    • On an average, 5 to 8% breakage happens on construction site, so 100% utilisation is not possible. Even at some places, due to the poor quality of bricks, wastage goes up to 20%.

    H. Storage

    AAC Block


    • Readily available at any time & in any season at a short notice, so no storage required.

    Red Bricks/Clay Bricks


    • In monsoon, Stock at the site is compulsory which blocks large working area on the site. otherwise work will get stopped.

    I. Efflorescence

    AAC Block

    • Efflorescence may occur through mortar and water.

    Red Bricks/Clay Bricks

    • Efflorescence may occur due to presence of salt in water and sand.


    09. Cost

    A. Construct a 1 Cum Wall Cost
    AAC Block

    1 cum block work cost is higher (around INR 3400/- in India).

    Red Bricks/Clay Bricks

    1 cum brick work cost is lower. (around INR 3200/- in India).


    B. Structural Cost

    AAC Block


    • Steel saving up to 15% & Concrete saving up to 7%.
    • AAC Blocks reduce the load on foundation due to its light self-weight and saves consumption of steel. Hence reduces the Structural Cost.

    Red Bricks/Clay Bricks


    • No such saving is possible


    10. Environment Impact

    A. Green Product

    AAC Block


    • AAC Blocks are made from a non-toxic material which does not harm the environment. Usage of fly ash helps in dumping of this-industrial waste. During the manufacturing process, Waste of the AAC Block is recycled and used again. This waste is made from the cutting process. Hence AAC Blocks are a Green product.


    Red Bricks/Clay Bricks


    • Red Bricks are made from the clay which is naturally available material but it reduces the top fertile soil cover. Hence, it is not eco-friendly.


    B. Earthquake Resistance

    AAC Block

    • Earthquake forces are proportional to the weight of the building. Since AAC Blocks reduce the weight of building, the safety against earthquakes is more.

    Red Bricks/Clay Bricks

    • Red bricks are not preferred in earthquake prone regions.










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