CHAPTER 1

INTRODUCTION

AAC was invented in mid-1923 in Sweden. It is also known as Autoclaved Cellular

Concrete (ACC) or Autoclaved Lightweight Concrete (ALC). Production process of

AAC is fairly simple. It is made with made with a mixture of fly ash, lime, cement,

gypsum, an aeration agent and water. Aeration process, imparts it a cellular light-weight

structure. AAC products are precast in various sizes and provide structure, insulation,

and fire and mold resistance.

AAC products are offered in various shapes and sizes including but not limited to

blocks, wall panels, floor and roof panels, and lintels. Use of Autoclaved Aerated

Concrete (AAC) blocks in construction industry in India offers interesting proposition for

various segments in the society. For a project developer it means faster and lower cost

construction. For environmentally conscious it means eco-friendly products and for those

who occupy buildings built with AAC blocks it means better safety and lower energy

costs for cooling or heating. Primary raw material for AAC is fly ash.

Thousands of tonnes of fly ash is generated by thermal power plants everyday and

its disposal is a cause of concern. Moreover, using fly ash does not harm the environment

at all. In fact using fly ash takes care of issues related to disposal of fly ash. Therefore by

using fly ash to produce AAC products provides a sustainable, economic and

environment friendly option. At the end it all translates to a better world for future

generations.

Fig no. 1

1.1 Types of Aerocon bricks

One interesting aspect of Aerocon brick is that it lets the user build the walls of with the thickness of his choice. Contrary to the wall made by traditional bricks, walls made with Aerocon bricks are thinner but are still sustainable.

However, depending on different various needs of internal and external walls, Aerocon bricks are available in different sizes and varied thickness as follows. Aerocon bricks are currently available in three sizes: Infill, Jumbo, and Thermal blocks

1.1.1 Infill blocks

The size of the Infill Aerocon brick is 600X600 mm and the thickness varies in the ranges of 75,100,125,150,200 mm. The main advantage of Infill blocks is that they can easily replace 60% of the concrete in roof slabs and thus help in saving significant amounts of concrete, steel, labor, water, plaster etc. These blocks are especially suitable for building roofs in large column-free constructions.

Fig no. 1.1.1

1.1.2 Jumbo blocks

Jumbo blocks are typically in the size of 600X300 mm, and thickness ranges from 75,100,125,150, to 200 mm. The unique large size of Jumbo Aerocon bricks results in the usage of much fewer bricks and hence less mortar is required. These bricks are more suitable for non-load bearing walls, multi-storeid buildings etc.

1.1.3 Thermal blocks

These blocks are also called as Aerocool thermal blocks whose size and thickness is 300X200 mm and 50 mm respectively. These blocks are ideal for roofing since they delay the transmission of heat flow and also help interiors remain warm during winters and cool during summers.

Fig no. 1.1.3

CHAPTER 2

COMPARISION BETWEEN AEROCON BRICKS AND

CLAY BRICKS

Comparison between Parameter AAC Blocks Clay BricksAutoclaved AeratedConcrete (AAC)blocks and claybricks Serial

1 Soil Consumption Uses fly ash which is a One sq ft of carpetthermal power plant area with clay brickwaste product & thus walling will consumeno consumption of top 25.5 kg of top soilsoil

2 Fuel Consumption One sq ft of carpet One sq ft of carpetarea with AAC blocks area with clay brickswill consume 1 kg of will consume 8 kg ofcoal coal

3 CO2 Emission One sq ft of carpet One sq ft of carpetarea will emit 2.2 kg of area will emit 17.6 kgCO2 of CO2

4 Labour Organized sector with Unorganized sectorproper HR practices with rampant use of

child labour5 Production Facility State-of-the-art factory Unhealthy working

facility conditions due totoxic gases

6 Tax Contribution Contributes to Does not contributegovernment taxes in to governmentform of Central exchequerExcise, VAT andOctroi

7 Size 625 mm x 240 mm x 225 mm x 100 mm x100-300 mm 65 mm

8 Variation in Size 1.5 mm (+/-) 5 mm (+/-)9 Compressive Strength 3.5-4 N/m2 2.5-3 N/m210 Dry Density 550-700 kg/m3 1800 kg/ m311 Fire Resistance (8" Up to 7 hours Around 2 hours

wall)12 Cost Benefit Reduction in dead None

weight leading tosavings in steel andconcrete

13 Energy Saving Approx.30% heating Noneand cooling

The advantages of Aerocon Bricks over Conventional Clay Bricks

Aerocon Blocks are an innovative product in the green building revolution.

Aerocon blocks are the new blocks in walling materials, substituting conventional and environmentally unsustainable materials like clay bricks, concrete and hollow blocks.

The raw materials used in the manufacture of these blocks are environmentally friendly and are certified green products. The basic raw materials used in production of Aerocon blocks are Cement, Fly ash, lime and water.

Aerocon blocks can be plastered, painted, and dry lined or tiled.

Aerocon block is extremely light, just one-third the weight of clay bricks or one-fourth the density of R.C.C. They are much easier to handle on the site.

They are easy to install and can complete the construction procedure in a shorter span in case of scarcity of labour and in the usage of mortars. The required time to complete a building with aerocon blocks is 1/3 lesser than that of the conventional building materials.

The edges of the blocks are such that they allow easy workability and accurate dimensioning and are easy to cut, drill, nail, shape and chase using ordinary wood working tools. Power tools can be used for rapid chasing for embedding service lines.

Aerocon blocks can be cut virtually in any shape or angle making them extremely

adaptable.

Aerocon block covers the same area as that 14 clay bricks do enabling a faster construction results in saving of labour, time and material.

Aerated concrete is perfect building material for any climate. It is used to build all kinds of walls: exterior and interior bearing and non-bearing walls, foundation walls, partition walls as filling agent in framework structures, wall partitions, fire division walls, etc.

Aerocon excellent thermal properties helps in saving recurring energy costs of heating and cooling. The thermal resistance combined with the benefits of thermal mass inertia and whole wall coverage eliminates the need for additional insulation.

Aerocon blocks are available in various sizes and shapes.They are available in three types; Infill blocks, Jumbo blocks and Thermal blocks. They are included into the category of Green Building materials because they don‟t emit VOC (Volatile Organic Compounds) which cause environmental pollution.

Apart from being eco-friendly these blocks are also light weight with high thermal insulation, fire resistance, sound insulation, have strength and durability, have consistent quality control and gives a perfect finish with dimensional stability. Buildings constructed out of these blocks ensure long term sustainability and save a lot of water during the construction.

Excluding the eco-friendly characteristics of these blocks, they are also used in construction for various other reasons. There are a number of problems involved in acquiring the sand and bricks and also the prices of these basic materials are hiking up. As the traditional construction materials have a higher price the initiation of Aerocon blocks acts as better substitutes with affordable prices. Due to these reasons the Aerocon blocks are in great demand.

Hence, it is one of the revolutionary materials that can be used to make the world a better, greener and cleaner place to live in. It is a revolutionary material that combines the unique properties such as durability and strength, low weight, very simple construction technology and excellent environmental performance.

CHAPTER 3

DESIGN CONSIDERATIONS

3.1 General considerationsAAC masonry components(block units) can be used to build load bearing or non load bearing walls.

O-block units used to build pilasters. U-block units used to build bond beams and lintels. Control joints on AAC reinforced walls must be placed at maximum 16 ft. o.c.

Installation Guide Check foundation. Receiving and distribution of AAC wall units.

Installation requirements Tools Equipment Other materials Installing O-block for pilasters in first course

Laying the first course (levelling course) Lay the first course over a semi-dry cement mortar levelling bed- ½” to 2” thick. Corner blocks are laid first and the first course should be completed before second

course installation. Once corner blocks are placed apply thin bed mortar, to the vertical joints for

other blocks. Thin bed mortar 1/16” inch to 1/8”

Cutting blocks (adjustments and chases) A hand saw or band saw to cut the blocks to specific lengths.

Placing control joints in first course These are vertical joints taken through the full wall thickness, and from bottom to top.

3/8” to ½” thick. Maximum spacing between control joints should be 15 ft.

Laying the subsequent courses For subsequent courses use only thin bed mortaring on all joints between AAC

blocks. Minimum overlapping of vertical joints between layers should be 4”. Metal strip ties should be placed every two courses at – 1) connection of secondary

walls to main walls – 2) connection of walls to concrete columns.

Control joints in subsequent layers

• V-shaped metal strips should be set at every two courses unless there are two pilasters on both sides of control joints and less than 2” from the joint.

• Once the wall is built fill the gap using backer rod and seal with caulking.

• Fill up pilasters by pouring concrete.

Building on site lintels using U-blocks • Install temporary supports before putting U-blocks in place apply thin bed mortar

to the vertical joints.

• Once U-block are set, place rebars according to construction drawings and with concrete.

Installing U-blocks to build bond beams• Lay U-block course applying thin bed mortar on all joints. • At each pilaster location, drill a hole in the bottom side so the vertical bars can be

attached in the bond beam. • Before pouring concrete place rebar and anchor bolts according to construction

drawings.

Utilities installation after the walls are built• For electrical conduits and piping installation, a chase is cut using an electrical

router or a chasing tool. • When required depth of chase is bigger than maximum depth recommended,

additional O-blocks are used to lodge the pipes or interrupt wall continuity. • After installation, the chase are filled with repair mortar or cement sand mortar.

Renders• Surface patching:

Rasp block joints and other areas where AAC surface is out of plane.• Surface must be cleaned using a scrub brush and any loose or damaged material be

removed. • A rubber float is commonly used to smooth the wall surface. • Fiber glass mesh:

This should be installed directly over one layer of render in all control joints, around windows, doors and utility locations.

Finishes

• AAC masonry walls can be finished with stucco , acrylic texture coats, or a combination of both, also laminated stones, ceramic or clay tiles, concrete pieces and ornamental products.

Fig no.3.1

3.2 Raw Material

Fly Ash or Sand

Key ingredient for manufacturing AAC blocks is silica rich material like fly ash or sand.

Most of the AAC companies in India use fly ash to manufacture AAC blocks. Fly ash is

mixed with water to form fly ash slurry. Slurry thus formed is mixed with other

ingredients like lime powder, cement, gypsum and Aluminum powder in quantities

consistent with the recipe. Alternately sand can also be used to manufacture AAC blocks.

A „wet‟ ball mill finely grinds sand with water converting it into sand slurry.

Sand slurry is mixed with other ingredients just like fly ash slurry.

Lime Powder

Lime powder required for AAC production is obtained either by crushing limestone to

fine powder at AAC factory or by directly purchasing it in powder form. Although

purchasing lime powder might be little costly, many manufacturers opt for it rather than

investing in lime crushing equipment like ball mill, jaw crusher, bucket elevators, etc.

Lime powder is stored in silos fabricated from mild steel (MS) or built using brick and

mortar depending of individual preferences.

Cement

53-grade Ordinary Portland Cement (OPC) from reputed manufacturer is required for

manufacturing AAC blocks. Cement supplied by „mini plants‟ is not recommended due to

drastic variations in quality over different batches. Some AAC factories might plan their

captive cement processing units as such an unit can produce cement as well as process lime.

Such factories can opt for „major plant‟ clinker and manufacture their own

cement for AAC production. Cement is usually stored in silos.

Gypsum

Gypsum is easily available in the market and is used in powder form. It is stored in silos.

Aluminum Powder/Paste

Aluminum powder/paste is easily available from various manufacturers. As very small

quantity of Aluminum powder/paste is required to be added to the mixture, it is usually

weighed manually and added to the mixing unit.

CHAPTER 4

PRODUCTION PROCESS

4.1 Raw Material Preparation and Storage

The first step of AAC production is grinding of silica rich material (sand, fly ash, etc) in

ball mills. For different materials, different processing is adopted, such as dry grinding

(into powder), wet grinding (into slurry) or mixed grinding with quicklime (CaO). There

are two methods for mixed milling.

One is dry mixing to produce binding material, and the other method is wet

mixing. Since most quicklime is agglomerate, it should be crushed and then grinded.

Gypsum is normally not ball milled separately. It is grinded with fly ash or with

quicklime, or it could be grinded with the same miller for quicklime in turn. Other

supplementary and chemicals are also have to be prepared. Raw material storage assures

the continuous production and material stability.

The continuous production guarantees the non-stop & on-time supply, and the

material stability guarantees the quality of products, since the raw material might come

from different sources, with different qualities. Raw material preparation & storage is the

pre-step for proportioning batching. This pre-step guarantees the raw material meet the

standard for AAC production, and it is also finishes the storage, homogenization and

aging process. It is the basic process that assures the smooth production and production

quality.

4.2 Dosing and mixing

Maintaining ratio of all ingredients as per the selected recipe is critical to ensure

consistent quality of production. This is accomplished by using various control systems

to measure and release the required quantity of various raw materials. A dosing and

mixing unit is used to form the correct mix to produce Autoclaved Aerated Concrete

(AAC) blocks. Fly ash/sand slurry is pumped into a separate container.

Once the desired weight is poured in, pumping is stopped. Similarly lime powder,

cement and gypsum are poured into individual containers using screw conveyers. Once

required amount of each ingredient is filled into their individual containers control system

releases all ingredients into mixing drum.

Mixing drum is like a giant bowl with a stirrer rotating inside to ensure proper mixing of

ingredients. Steam might also be fed to the unit to maintain temperature in range of 40-

42o C. A smaller bowl type structure used for feeding Aluminium powder is also

attached as a part of mixing unit. Once the mixture has been churned for set time, it is

ready to be poured into molds using dosing unit. Dosing unit releases this mixture as per

set quantities into molds for foaming.

Dosing and mixing process is carried out continuously because if there is a long

gap between charging and discharging of ingredients, residual mixture might start

hardening and choke up the entire unit. In modern plants, entire dosing and mixing

operation is completely automated and requires minimum human intervention.

This entire operation is monitored using control systems integrated with

computer and CCTV cameras. As with any industrial operation, there is provision for

human intervention and emergency actions integrated inside the control system.

4.3 Casting, Foaming and Pre-curing

Once the desired mix is ready, it is poured into moulds. These moulds can be of

various sizes depending on the production capacity of a manufacturing unit. Once mix is

poured into moulds, it is ready for pre-curing. After casting, the slurry in molds will be

in the pre-curing chamber to finish foaming and hardening. Foaming and hardening

actually starts when the slurry is fed into molds, which includes gas-forming expansion

and perform, curing to achieve certain strength, which is enough for cutting. Pre-curing

is always done under set temperature.

Hence it is also called as “Heating-room-pre-curing.” Pre-curing as not a

complicated process, but should avoid vibration. Operations must keep eyes to monitory the

slury change during foaming and provide feedback to dosing, mixing and casting process.

Pre-form defects (cracking, sinking, etc.,) mainly occur during the process.

4.4 Cutting

During this process, the pre-cured block goes through cutting and shaping, into different

size & shapes as per requirements. The high workability and large variety of sizes make

AAC production more suitable for massive production with higher mechanization.

Cutting can be done mechanically or manually. With a cutting machine, the production

efficiency and dimensional accuracy is easily achieved.

4.5 Autoclaved Curing

After cutting into the desired sizes & shapes, „green‟ AAC blocks are transferred into

autoclaves. Autoclaves are used for steam curing under pressure. AAC must be pre-cured

and steam cured to finish the physical and chemical changes, and then to achieve enough

strength for desired usage. A batch of AAC blocks is steam cured for 10-12 hours at a

pressure of 12 bar and temperature of 190°C. In hot and humid conditions, AAC blocks

undergo last stages of hydro-thermal synthesis reaction to transform into a new product

with required strength and various physical performances. Autoclaved curing imparts

inherent properties and performance of AAC.

4.6 Grouping

Grouping could be the last step of AAC production (in some AAC plant, the AAC will be

further processed into panels after leaving autoclaves). After the cured AAC leaves the

autoclaves, inspection and packaging is done.

Process Flow Chart.

CHAPTER 5

ANALYSIS

5.1 Market

Shelter is third skin, according to a German Concept, which implies its importance next

to human Skin and Clothing. This also shows the attachment of human race to this

fundamental requirement.

Building Material accounts for major component of the construction cost. Depending

on the location they can contribute to 60 - 70 % of the cost of construction. With the ever

increasing population, the demand for housing increases. This directly creates demand for

this prime commodity of building.

Add to the above fact the nearby area of this project site is undergoing a major

infrastructure revolution. As Residential, Commercial, IT companies, and Industrial

establishments are coming in, we can conclude that the Blocks unit will prosper and

flourish in this environment.

There is a central government gadget notification mandating government departments

and CPWD to use 100% Fly Ash based Bricks in their all constructions-directly of

through contractors. This factor will help the marketability of this product immensely.

Fly Ash policy of the Government also mandates that 20% of Fly ash Generated by a

power plant must be given free of cost to SME sector on a priority basis.

5.2 Carbon Credits Estimates

AAC blocks are being seriously considered for CDM projects in India for earning Carbon

Credits. As the CER Generated is also relatively less, four or five such units can be

bundled together to make a Group CDM in the same sactors.

This project is likely to generate 1 CER per each 7 or 8 Cubic Meter of Blocks

production, depending on, and subject to the CDM methodology adopted, and the

interpretation of additionality and baseline parameters by the validating authority.

Just for a rough estimate of CERS, for an annual production of average size AAC plant,

that is 100000CM/Annum, we are likely to get around 12500 CERs on full capacity

Production. At present market rate of 11.5 Euros per CER and @ Rs. 60 per Euro, we can

expect to get additional revenue on CER. But we must expect to take a cut of around 20

to 30% of CERs, if we want to forward sell the CERs and get the CDM part sponsore the

buyer.

5.3 Raw Material Suitability

Almost 95% of the raw materials can be made suitable for AAC line through proper mix

design. Also we can have many different mix designs for the same denicity…same

strength of Blocks. We will help you to get the Best quality blocks at optimal cost by

means of designing proper Mix as per your input raw materials.

The following are basic guidelines (certainly not the final call) on the suitability of basic

raw materials for AAC.

1. Fly ash (65-70%)

Index Item Grade (%)

Gr-I Gr-II

(0.045 square hole sieve left

Degree of amount) ≤ 30 45

(0.080 square hole sieve left

fineness amount) ≤ 15 25

Ignition loss ≤ 5.0 10.0

SiO2 ≥ 45-55 40

SO3 ≤ 1 2

Reference : The fineness can be 0.045 or 0.080 square sieve left amount.

2. Lime (8-25%)

Item Grade

Super Gr. 1st Gr. 2nd Gr

A(CaO+MgO)Quality Fraction % ≥ 90 75 65

MgO Quality Fraction % ≤ 2 5 8

SiO2 Quality Fraction % ≤ 2 5 8

Digestion

speed5-15

,min ≤

Digestion temperature ,℃ ≥ 60-90

Undigested residue quality fraction ,% ≤ 5 10 15

Fineness (0.080 square hole sieve left amount) % ≤ 10 15 20

CO2 Quality Fraction % ≤ 2 5 7

3. Cement (6-15%)

SiO2 Al2O3 Fe2O3 CaO MgO C3S C2S C3A C4AF

21-23 5-7 3-5 64-48 4-5 44-59 18-30 5-12 10-18

4. Gypsum/Plaster (3-5%)

CaSO4 ＞ 70%

MgO ＜ 2%

Chloride ＜ 0.05%

Preferably ground residue 90µm ＜ 10-15%

5. Aluminum Power (about 0.08%)

Type and recommendation for supply depend on raw materials and mix formula

Metal Content Approx.>=65

% Powder

CHAPTER 6

Indian Standard for AAC blocks

Bureau of Indian Standard Code no- 2185(Part-3):1984 discusses in details regarding the

AAC blocks specifications in India. The prime requirements for AAC blocks (of ISI

standards) in India as per the above said code are as follows.

6.1. ON PHISICAL SIZES OF AAC BLOCKS

Concrete BlockConcrete Block shall be referred to by it’s nominal dimensions. The term

“nominal” means that the dimension includes the thickness of the mortar joint. Actual dimensions shall be 10mm short of the nominal dimensions (or 6mm short in special cases where fine joining is specified). The nomianal dimensions of the concrete block shall be as follows:

Length 400,500 or 600mmHeight 200,250 or 300mmWidth 100,150,200 or 250mm

In addition, block shall be manufactured in half length of 200,250 or 300mm to

correspond to the full lengths.

6.2 ON TOLERANCES OF AAC BLOCK SIZES

The maximum variation in the length of the units shall not be more than +5mm or -5mm and the maximum variation in the height and width of unit, not more than +3mm or -3mm.

6.3 ON DENSITY, STRENGTH & THERMAL CONDUCTIVITY

SNo. Density in Owendry Condition

CHAPTER 7

ADVANTAGES AND DISADVANTAGES

7.1Advantages of using Autoclaved Aerated Concrete

7.1.1 Lightweight

AAC blocks are about 50% lighter than clay bricks of equivalent size. This

translates into less dead weight of buildings and allows entire structure to be lighter

therefore reducing amount of steel and concrete used in structural components like

beams, columns and roof/floor slabs.

Fig no. 7.1.1

7.1.2 Single Product Solution

Buildings constructed with AAC do not require separate insulation products

reducing construction cost, energy footprint and environmental impact of buildings.

7.1.3 Easy Workability

AAC is very easy to work with and can be cut accurately reducing the amount

of waste generated.

Fig no. 7.1.3

7.1.4 Environmental Impact

Manufacturing of AAC does not have high energy requirements. Moreover since

AAC is light weight, it also saves energy required for transportation and leads to reduced

CO2 emissions by transport vehicles. Since AAC is made from fly ash – an industrial

waste product – generated by thermal power plants, it offers a low cost and sustainable

solution for today and tomorrow. AAC is a requisite for green buildings.

7.1.5 Easy Transportation

It is easy to transport AAC as it does not suffer from high transit breakage

usually associated with clay bricks.

7.1.6 Longevity

AAC does not lose strength or deteriorate over time. Buildings constructed with

AAC do not require routine repairs that are required for buildings using clay bricks.

7.1.7 Shorter Project Duration

Buildings can be built with AAC 50% faster compared to clay bricks. This

translates to lower project completion times benefiting project developers.

7.1.8 Thermal Insulation

AAC offers excellent thermal insulation. This reduces recurring cost of energy

required for heating and cooling. Better thermal insulation also allows usage of smaller

HVAC than required conventionally.

Fig No 7.1.8

7.1.9 High Survivability

Millions of air pockets in AAC cushion structure from major force and

prevents progressive collapse of a building. AAC structures are known to maintain

structural integrity despite of heavy rains, extremely low temperature and salty air.

7.1.9 Fire Resistance

Due to high fire resistance offered by AAC, structures made from AAC have

higher rate of survivability in case of fire.

Fig no. 7.1.9

7.1.10 Sound Insulation

Sound absorption properties of AAC make it ideal material for reducing

ambient noi se.AAC is well-suited for establishments like hospitals and offices

situated in noisy areas.

Fig no. 7.1.10

7.1.11 Contribution to Nation

AAC factories create many jobs directly and indirectly creating a social impact.

Along with that they pa

7.1.12 Weather Resistance

AAC does not decay, rust, deteriorate or burn. AAC has been found to be

earthquake resistant. AAC structures are known to maintain structural integrity in heavy

rains, extremely low temperature and salty air.

7.1.13 Pest Resistance

Primary raw material used to manufacture AAC is fly ash. Fly ash (or pond ash) is

an inert material and does not allow termites or other pests to survive.

Excise Duty and VAT contributing to national economy

Fig no. 7.1.13

7.2 Product Disadvantages

The major disadvantages of autoclaved aerated concrete are listed below.

The production cost per unit for ACC is higher than other ordinary concrete.

Number of manufacturer is limited. So, cost will drastically increase in places far from the manufacturer and need to travel a long distance.

It is not as strong as conventional concrete.

Very few contractors who are familiar with ACC.

Construction with autoclaved aerated concrete may will need special permission.

Environmentally friendly

CHAPTER 8

CONCLUSION

As a construction system, AAC provide significant environment and other benefits for the building owner. The short and long term effect of using AAC compared to many other materials results in lower energy consumption, reduced operating costs, greater safety and comfort, and a healthier and more trouble – free building. These features provide a better investment for building owner and for environment.

REFERNCES