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AAC blocks

AAC blocks vs red bricks – An ultimate comparison.

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AAC Blocks vs red bricks – AAC blocks or Autoclaved Aerated Concrete Blocks are lightweight, load-bearing, durable, and an economical product that can be manufactured to meet any requirements. AAC blocks are considered as a green option in place of red bricks because of their enormous potential in terms of insulation, fire-resistant, and thermal resistant properties and are environmentally friendly and superior material compared to concrete, wood, brick, and stone. They can enhance the construction speed, reduce the costs, and unwanted wastage at construction sites.

AAC blocks are superior to conventional red clay bricks in a lot of factors. Considering the impact and necessity of these factors we can easily make a choice.

AAC blocks vs red bricks

AAC blocks are superior to red bricks in a lot of factors relating to quality, speed, workability, cost, and wastage. There is a plentiful to brief on the advantages of AAC blocks over Red bricks, fly ash bricks, Cement Concrete hollow blocks, and CLC blocks.

a) Availability of sizes.

Customisation in size is the most important aspect in deciding the choice of bricks/blocks for a particular structure.

AAC blocksConventional red bricks
AAC blocks are available in varied sizes are can be customised for special requirements.Mostly available in one or two standard sizes. No customisation is possible.

b) AAC blocks vs red bricks- Technical properties

AAC BLOCK DIMENSIONS
AAC BLOCK DIMENSIONS
RED CLAY BRICK DIMENSIONS
RED CLAY BRICK DIMENSIONS
AAC Blocks Conventional bricks
AAC blocks are available in 600mm/625mm (length) X 100 – 300 mm (height) x 230/240 mm (width).Bricks are available in 225 mm (length) x 115 mm (width ) X 75/70 mm (Height).
The dimension tolerance of the AAC block is +/-5 mm.The dimension tolerance of brick is +/- 5 mm to +/-15 mm or more.
Density ranges between 500-650 kg/cm3.Density ranges between
1400-1900 kg/cm3
The Drying shrinkage of AAC blocks is 0.4% which is very low in comparison with Conventional bricks.The drying shrinkage of bricks is 0.8% which is comparatively high compared with AAC blocks.

c) AAC blocks vs red bricks – Construction speed

AAC blocks are considered cost-effective and economical in comparison with conventional bricks. The cost-effectiveness of AAC blocks is mostly related to the construction speed.
AAC blocks can enhance construction speed when compared to conventional bricks and are due to some unique characteristics detailed out in the following table.

AAC blocks vs red bricks
AAC blocks vs red bricks

Let us take a wall of 3mtr x 3 mtr size and 4 inch thickness

AAC BlocksConventional Bricks
Area of block = 24 inch x 9 inch
(600 mm x 230 mm) = 0.138 sqm
Wall area = 3m x 3 m =9 sqm
No of blocks = 9 sqm/0.138sqm =
65 blocks
(600 mm x 230 mm x 100 mm) size		Area of brick is 9 inch x 3 inch
(230 mm x 70 mm) = 0.0161 sqm
No of bricks = 9 sqm / 0.0162=
555 bricks
(230 x 110 x 70 mm) size
Total mortar joints
85 rmt (approx)		Total mortar joints
170 rmt for 4 inch wall &
240-250 rmt for 9 inch wall
Weight of an AAC block (9 inch)
16-17 kg for a 9 inch thick block		Weigh of brick = 3-3.5 kg (approx)
1 no 9 inch block = 14-15 bricksBricks are heavy

From the above comparisons, it is clear that the AAC blocks are lightweight and covers more area than bricks. Brick masonry got 3-4 times higher mortar joints and around 14-15 bricks constitute an AAC block. That is why Brick masonry is very slow.
AAC blocks are big, got fewer joints, and can be completed very fast.

Factors influencing construction speed

AAC blocks are factory-made and posses dimensional accuracy. They are easy to place and plumb.Red bricks are locally made and are irregular with less dimensional accuracy. Bricks are very difficult to place, level, and plumb.
AAC block got fewer joints and hence construction speed is high.Red Brick got a larger number of joints (4 times) in comparison with AAC blocks and hence construction speed is drastically reduced.
AAC blocks cover larger areaBricks cover less area
AAC blocks can even be placed with semiskilled workers due to there dimensional accuracy and shape.Bricks work can be done with the help of a skilled mason only, due to the inaccuracy and shape issues.
AAC blocks mostly use block adhesive for bonding and are available in ready mix packs. The thickness of mortar joints ranges between 3-5 mm.Brickwork is done by site mixed mortar and has to be a minimum of 10 mm. The mortar thickness is high in the case of brickwork.

d) Savings in labour

Pre curing and post curing labour

AAC blocks do not require any pre-curing. AAC block masonry joints are air-cured and need not require any curing. Infrastructure and labour involved in the curing process can be eliminated.Bricks have to be soaked in water before using it in works. Moreover, 7-day curing has to be done on brickwork. This requires setting up of curing infrastructure, and tabor involvement.

Labour saving in mortar mixing

AAC blocks use ready-mix bonding
adhesive as jointing material. They are
available in 25-30 kg packs and to mix
with water before use.		Brickwork uses site mix mortar that involves handling, mixing, and conveying of raw materials, and mortar.
This can save substantial tabor cost incurred for mortar mixing and conveying.Extra tabor cost involvement for mortar mixing and conveying.
Mortar mixing
AAC BLOCKS VS RED BRICKS – MORTAR MIXING

Conveying and re-handling labour

AAC blocks are supplied in pellets and can be easily lifted and conveyed to the work spots using cranes and tower
cranes directly from the trucks.		Bricks are supplied in loose and are unloaded & conveyed manually to different places. They have to be filled in buckets before lifting to heights and involves lots of labour.
Saves labour involvement in unloading, conveying, and lifting.
Less handling generates zero wastage.		Bricks shifting and conveying involves a lot of labour and generates a huge amount of wastage.

AAC block work rates are comparably less than brickwork due to the saving involved in the labour part. The rate per cum of AAC blocks will be around INR – 650/- to -750 /- per cum whereas brickwork is around INR 1400-1500/- per cum.

e) Material saving

Saving in mortar

AAC blocks got fewer mortar joints of 3-5 mm thickness whereas brick masonry generates 3-4 times higher number of joints of 12 mm thickness. This can save substantially in terms of jointing material.

ANALYSIS OF MORTAR FOR RICKWORK     
1 CUM Brick work = 0.35 to 0.4 cum mortar     
Sand cost (Rs.2500/- per cum)0.35x2500.=875
cement1.3x300.=390
total cost per cum of brick work   INR 1265/-
ANALYSIS OF BLOCK ADHESIVE
1 CUM block work = 30 kg of block adhesive
Rate per kg =  Rs. 12-15 per kg
Cost for 30 kg = around INR-400/-per cum

Block adhesive cost 400/- per cum whereas mortar cost is around Rs. 1250/- per cum.

Saving in plastering

AAC blocks are dimensionally accurate and both faces of the block-work look even without any undulations. The undulations can be levelled by providing a minimum plastering thickness of 10 mm inside and 12-15 mm outside. AAC blocks can even be painted by directly applying putty/Gypsum plaster over it.

Brickwork has a fair face and unfair face. For covering up of undulations a 12 mm plastering thickness is required for the fair face whereas a minimum 18 mm thick is required for an unfair face.

There are also other value added benefits of AAC blocks which points out AAC blocks as a superior fire resistant, termite resistant, thermal resistant and green building material . Please read ADVANTAGES OF AAC BLOCKS.

Also read : MANUFACTURING PROCESS OF AAC BLOCKS

AAC blocks, Building materials

Advantages of AAC blocks – A Superior Brick Alternative

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The advantages of AAC blocks over other alternatives stamps it as a perfect and superior building material in comparison with conventional bricks. Advantages of AAC blocks and their properties are listed out in detail.

Advantages of AAC blocks

AAC Blocks or Autoclaved Aerated Concrete Blocks are lightweight, load-bearing, durable, and economical walling material. They are eco-sensitive and green option to bricks, due to its enormous potentials in terms of insulation, fire-resistant, acoustic, and thermal resistant properties. AAC Blocks are superior material when compared with concrete, wood, brick, and stone. They can enhance the construction speed, reduce the costs, and minimise wastage at construction sites.

Also read : MANUFACTURING PROCESS OF AAC BLOCKS

Technical Advantages of AAC blocks

The unique qualities of AAC blocks are mainly due to its properties. AAC blocks are something more than a brick alternative. AAC block posses a lot of qualities that make them stand out from other alternatives. The advantages in terms of technical properties are listed below.

AAC blocks sizes are customised and manufactured in various sizes. The most common dimensions available in the market is :
600/625 mm (length) x 230/240 mm(height) x 100 mm-300 mm (thick)

TECHNICAL ADVANTAGES OF AAC BLOCKS
TECHNICAL ADVANTAGES OF AAC BLOCKS

Dimension and appearance

The biggest advantages of AAC blocks are its Dimension and appearance.

AAC Blocks are factory manufactured and hence got a perfect size and finish with a dimension tolerance of +/- 5mm. They have sharp edges and corners, uniform colour, and pleasing appearance. 

AAC block density is around (550-650)kg/cm3 which can be customised as per requirement.

AAC blocks pose a drying shrinkage of around 0.4 % which is considered very less when compared to conventional bricks.

Dimension optimisation is the main feature of AAC blocks. They can be customised to cater to any dimension requirements. AAC blocks are available in thickness ranging from 100 mm to 300 mm with a standard length of 600 mm/625 mm. The dimensions of AAC blocks also differ with the manufacturer. 

Fire resistant advantages of AAC blocks

AAC blocks are non-combustible and got excellent fire-resistant properties. The melting point of the AAC blocks is around 1600 degrees Celsius which is much higher than the temperature of building fires, where it is around 500 degrees Celsius. AAC block can withstand fire up to 4-6 hours depending on the block thickness.

ADVANTAGES OF AAC BLOCKS DURING FIRE
ADVANTAGES OF AAC BLOCKS DURING FIRE

Acoustic/Sound proof qualities

AAC Blocks possess low density and high porosity due to the presence of billions of voids. The voids make up 80% of the total volume. The AAC block got high sound absorption properties when compared with any other building materials like concrete and brick due to its high porosity.

The high acoustic properties make AAC blocks a preferred choice for cinema halls and auditoriums walls.

Insect and termite resistant

AAC Block uses inorganic materials like fly ash, cement, gypsum, etc as ingredients in its manufacturing process. AAC block possesses good insect and termite resistant qualities due to the presence of these inorganic materials.

Advantage of AAC blocks – Thermal insulation and energy savings

Fly ash is the main ingredient and constitutes more than 70% weight of AAC blocks ingredients. The micro pores constitutes around 80% of AAC blocks accounts for its excellent thermal insulation properties. The thermal insulation qualities help in maintaining inner temperature cool in summers and warm in winters. More cooler interior means less AC load which in turn can reduce energy consumption by 20% and can eliminate costly thermal insulation.

Advantage of AAC block-Impact of earthquake

AAC blocks are lightweight and reduces dead load/ mass on the structure. The impact of earthquake is directly proportional to the weight of structure. Because of its light weight properties, AAC blocks can reduce the impact of earthquake to an extend and hence preferred for earthquake zones.

Water and Moisture Resistant

AAC blocks constitutes millions of micro pores which prevent capillary transport of water and moisture over a long distance. The walls can resist moisture even with a lesser thickness compared to bricks. The water and moisture resistant qualities enable to use a less thick block as partitions.

Advantage of AAC block in terms of strength

AAC blocks are highly superior in terms of the strength. Higher level of strength of these blocks gives higher stability to the structure of the building. 

Economical compared to any other alternative

AAC blocks are economical and stands out as the preferred option due to a lot of factors. This is the main advantage of AAC block over conventional red bricks.

CUTTING OF AAC BLOCK
CUTTING OF AAC BLOCK

Ease of cutting and chasing

Using recommended tools we can easily cut,drill and chase AAC blocks . The blocks will not break,crack or de-bond from its position while doing so.

Ensure fast construction

AAC blocks are lightweight, easy to fix and have a very accurate dimensional tolerance +/-5 mm and can be fixed, jointed and plumbed easily.

A single block of any thickness have an area of 24 inches x 8 inches

For completing a wall of 10 ft x 10ft

Surface area of block = 24 inch x 8 inch = 0.6 m x 0.2m = 0.12 sqm per block

Area of wall : 10 ft x 10 ft = 100 sq ft = 9.29 sqm

Quantity of block for an area of 9.29 sqm

9.29 sqm/0.12 sqm = 77.41 blocks for 100 sqft

Ordinary brick area is 9 inch x 3 inch = 0.23 m x .075 = .01725 sqm

Area of wall = 9.29 sqm area = 9.29/.1725 =

538 bricks (for 4 inch thick wall) and 1080 bricks for a 9 inch wall)

Higher the number of bricks greater the number of mortar joints.

AAC blocks are big in size and it can cover 13-14 bricks with a block. This can speed up the construction.

Advantage of AAC block in terms of Labour cost

PLACING OF AAC BLOCK
PLACING OF AAC BLOCK

AAC blocks are very fast and easy to place due to the less number of joints when compared with bricks.

AAC blocks doesn’t require any soaking before placing for masonry and no curing is required after carrying out the works. The block adhesive used is air cured . This can reduce substantial labour and infrastructure costs involved in curing and soaking of blocks.

AAC block uses ready mix block adhesive in place of mortar for bonding the blocks, wherein mortar making requires handling of aggregates, mixing and conveying to the location for use. The labour involved in this lengthy process can be saved in the case of AAC blocks. More over the area looks neat and clean as site mixed mortars tends to generate a lot of waste.

Bricks got 4 times more mortar joints than AAC blocks. The dimensional tolerance of bricks are very high around +/- 5 mm to 15 mm and more. It is difficult to plumb and place in position.

AAC block work can even be done with a semiskilled labour with a little bit of training mostly due to their dimensional accuracy.

AAC blocks are available in pallets and can be conveyed and lifted to any location with the help of cranes and tower cranes. This can save labour involvement in carrying of blocks.

Because of these factors the labour charges for placing AAC blocks are almost 50% less when compared with conventional bricks/ or any other walling material.

Advantages of AAC block – Savings in material cost

Saving in jointing mortar

The block adhesive joint thickness is around 3-4 mm and it is much cheaper than mortar which includes cement and sand and its mixing.

Saving in plastering material

There is a huge amount of savings in terms of plastering. AAC blockwork presents a fair face on both sides of wall whereas brick work generates a fair face and unfair face on the walls. For covering the unfair face of brickwork the thickness of mortar should be adjusted to a minimum of 18 mm or more. In case of AAC blocks due to its dimensional accuracy they can be covered even with 10 mm thick mortar on inside faces and 12 mm thick mortar for outside faces. AAC blocks comes in perfect shapes and can even be painted directly after applying POP or gypsum plaster in very thin coats.

PLASTERING OF AAC BLOCKS
PLASTERING OF AAC BLOCKS

Wastages

AAC block wastage is around 2% whereas brick wastage is around 10% to 15% which is relatively very high. This can generates substantial saving in terms of wastage and removal of debris.

Design optimisation

AAC blocks are light weight with very less density of around 600 kg/cm3. Structural designers can optimise their designs due to less dead loads similarly optimised design consume less steel and concrete.

Eco-friendly and green product

AAC is 100% Green building material & is a walling material of a choice in LEED certified buildings.
AAC is most energy & resource efficient in the sense that it uses least amount of energy in manufacturing and material per cum of product.
Brick manufacturing process uses fertile topsoil wherein AAC uses Fly-ash (65% of its weight) which is an industrial waste harming the environments.

AAC Blocks is a unique and excellent building material due to its superior heat, fire and sound resistance qualities. AAC blocks are lightweight and offers ultimate workability, flexibility and durability.

VIDEO : AAC BLOCKS VS RED CLAY BRICKS

AAC blocks, Building materials

AAC blocks Manufacturing Process – A remarkable green initiative

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AAC Blocks or Autoclaved Aerated Concrete Blocks are a lightweight, load-bearing, a durable, eco-sensitive, and economical alternative for conventional bricks. AAC Blocks can be customised to satisfy dimensional requirements. When compared to concrete,wood ,brick and stone AAC block possess excellent insulation, fire-resistant, and thermal resistant properties. AAC block can enhance construction speed and reduce costs.

AAC BLOCK LAYING
AAC BLOCKS LAYING

AAC Blocks Manufacturing

AAC block constitute 80% voids and hence it is lightweight and easy to handle. They are manufactured using easily available materials. The ingredients include sand, fly ash, lime, cement, gypsum, and aluminum powder. The manufacturing process is clean and does not emit any hazardous chemicals. Major raw materials used for AAC block manufacturing are industrial wastes like fly ash and gypsum. The manufacturing process is energy efficient eco-friendly certified green building materials.

Ingredients of AAC blocks

The main ingredients of AAC blocks are Fly ash, Sand, Cement, Lime, Gypsum, water, and aluminum powder. Aluminum powder is used as a foaming agent.

Cement used for AAC block manufacturing is OPC 43 or OPC 53 grade cement and is used as a binding material.

Fly ash is an industrial waste from power plants. The density ranges from 600kg/cm3 to 1400kg/cm3. The presence of fly ash is responsible for imparting insulation and fire-resistant properties of AAC blocks.

The lime is obtained by grinding limestone in the block manufacturing factory or outsourcing as lime powder.

Aluminum is used as a foaming agent and is responsible for the development of voids inside the blocks.

Gypsum is an industrial waste generated from fertiliser plants and is abundantly available.

AAC Blocks manufacturing process

The manufacturing process of AAC blocks is associated with a series of operations starting from, feeding of ingredients to the stacking of blocks. Every stage is associated with strict manufacturing quality guidelines for ensuring requisite strength and density. AAC block manufacturing processes are broadly classified as follows.

  • Raw material preparation
  • Dosing & mixing
  • Moulding, rising and pre-curing
  • De-moulding and Wire cutting
  • Autoclaving

Raw material Preparation

The basic ingredients required for AAC block manufacturing are fly ash or sand. Fly ash is abundantly available as industrial waste from power plants. Hence fly ash is used for manufacturing AAC blocks. It is mixed with water to form fly ash slurry which is stored in containers for the next stage of operation.

Dosing and mixing

The fly ash slurry is stored in a container which is connected to a mixing drum. All other ingredients like lime powder, gypsum, and cement are stored in different storage containers and are fed into the mixing drum using screw conveyors. Automatic feeding systems are attached to each storage container to ensure correct ingredient proportions. The proportioned ingredients are simultaneously fed to a mixing drum where it is mixed thoroughly. Aluminum dosing is done through a feeding attachment and is controlled according to the requirement. The ingredients are thoroughly mixed and ready to be poured into the moulds.

MIXING DRUM
MIXING DRUM

Moulding, rising and Pre-curing

The casting of AAC blocks is done in moulds. The moulds are cleaned and coated with oil to avoid any sticking of the ingredients on the surfaces of the mould which in turn can hamper the surface finish of blocks. Already mixed slurry is poured into the oiled moulds.
Inside the moulds, the aluminum reacts with calcium hydroxide (lime) and water and produces a lot of unconnected hydrogen bubbles and expands the slurry. The expansion is almost twice that of the original volume. This process is called rising. These hydrogen bubble spaces are responsible for the lightweight characteristics of AAC blocks. The process of rising is followed by de-moulding and cutting the blocks.
The cutting of the blocks into the required sizes requires some strength for the cube. For that, the mould is allowed to settle and cure for a while just enough for the wire cutting process. The pre-curing time can be anywhere between 1-3 hours or more depending on weather conditions.
This can be done by indirect heating also. After the pre-curing process, the green cake is strong enough for a wire cut.

De-moulding and Wire cutting

The pre-cured moulds are carried to the cutting area. The moulds are removed and the green cake is wire cut as per the required sizes. The wire cutting process is done in two stages. The first stage is a vertical cut and the second stage is a horizontal cut. De-moulding and cutting give the dimensional perfection and finish of the AAC blocks. This process has to be done with utmost care or else rejection may happen.

WIRE CUTTING OF AAC BLOCKS
WIRE CUTTING OF AAC BLOCKS

Autoclaving of AAC blocks

The final process of manufacturing is autoclaving. The wire cut blocks are transported to an autoclaved chamber where is heated to the required temperature. This process gives the desired durability and structural stability to AAC blocks. The baking is done for about 8-12 hours at a temperature of around 180 degrees. The temperature and period of heating determine the grade of the materials. Curing in an autoclave reduces drying shrinkage.The autoclave curing process requires more energy and a more expensive kiln, but it can produce blocks in less time.

The blocks are stacked on pellets on completion of autoclaving process for transporting to the required destinations. All quality tests are conducted in the factory itself.

AUTOCLAVING MACHING
AUTOCLAVING MACHINE

AAC Block Manufacturing Process

AAC BLOCK MANUFACTURING PROCESS

AAC BLOCK ADVANTAGES OVER RED BRICKS

ADVANTAGES OF AAC BLOCKS