Successfully reported this slideshow.
Your SlideShare is downloading. ×

Autoclaved Aerated Concrete

Upcoming SlideShare
Artificial Intelligence.pptx
Artificial Intelligence.pptx
Loading in …3

Check these out next

1 of 40 Ad

More Related Content

Recently uploaded (20)


Autoclaved Aerated Concrete

  1. 1. Autoclaved Aerated Concrete CV895 - MODERN CONCRETE MATERIALS AND TECHNOLOGY PRESENTED BY: Sanket Bhame Bhaskar Bhatia Mokshika Chopra
  2. 2. Introduction History Cellular Structure and Composition Production and Manufacturing process Characteristics and Properties Laying of AAC Comparative Analysis Advantages and Limitations Plant Locations across India References CONTENTS
  3. 3. INTRODUCTION Autoclave - an apparatus in which special conditions (such as high or low pressure or temperature) can be established for a variety of applications especially: an apparatus using steam under high pressure. (Ref. Mariam–Webster Dictionary) AAC blocks have a porous and lightweight texture AAC blocks are created and fed to an autoclave to harden MANUFACTURING PROCESS OF AAC BLOCK
  5. 5. 1. Autoclaved Aerated Concrete (AAC) has a porous structure created by small air bubbles by foaming agents or aluminum powder in cement, fly ash, and sand slurry and cured in high-pressure steam (autoclaved). 2. AAC blocks are 2-3 times lighter than traditional bricks. Incorporation of pozzolanic materials like fly ash into cement or concrete provides advantages such as reduction in heat, low permeability, and resistance to sulfate attack. 3. Fly ash is also used to replace part of Portland cement and part of fine aggregates for the production of AAC blocks. 4. These Blocks have low density and low thermal conductivity compared to clay bricks or concrete blocks. 5. There are many advantages of Aerated Concrete blocks such as reduction of dead load, faster building rate, and lower transport cost. 6. Other advantages include a relatively high strength-to-weight ratio, availability, fire resistance, good thermal resistance, and high sound insulation value. 7. Aerated concrete blocks are masonry units used in the construction of partition/non-load-bearing walls in RC framed buildings using cement mortars. 8. Autoclaved Aerated Concrete (AAC) Blocks are manufactured in specialized manufacturing facilities in various sizes. INTRODUCTION .
  6. 6. HISTORY He was working on aerated concrete samples, and that’s when the accidental discovery occurred. Running short of time, he decided to speed up the curing process. He placed one of his samples of burnt shale limestone, water, and aluminum powder in the laboratory autoclave. The porous mass survived the overnight autoclaving, and the resulting cured concrete possessed greatly increased strength and a new, stronger crystalline composition. In the heat and pressure of the steam curing, the silica and lime components fused to form a calcium silicate hydrate crystal, similar to the volcanic rock, Tobermorite. (For more info refer to notes of the slide) An Accidental Discovery Autoclave aerated concrete blocks are also known as autoclaved lightweight concrete(ALC) Autoclaved Aerated Concrete (AAC) is one of the eco–friendly and certified green building materials. AAC was perfected in the mid of 1920s by the Swedish architect, Dr. Johan Axel Ericksson. The process was patented in 1924.
  7. 7. HOW IS CELLULAR STRUCTURE FORMED  Generation of the cellular structure is normally done through the addition of aluminum powder as the mixing procedure is ending.  The aluminum powder in the alkaline medium (due to the cement or lime) produces hydrogen gas which, in turn, generates the cells.  The addition of the aluminum powder is controlled so that gassing does not begin during mixing but during the molding stage.
  8. 8. COMPOSITION OF AAC 1. Cement 2. Fly-Ash 3. Quartz Sand (Sio2 with Impurities) 4. Calcined Calcium Sulfate (Gypsum/Plaster Of Paris) 5. Aluminum Powder/Hydrogen Peroxide 6. Lime (Cao) 7. Water MANUFACTURING PROCESS OF AAC BLOCK 1 2 3 4 6 5
  9. 9. CHEMICAL COMPOSITION AND PROPORTION OF RAW MATERIALS Compound Chemical Composition (In%) CaO 57.84 SiO2 20.33 Fe2O3 4.68 Al2O3 3.40 MgO 1.51 MnO 0.10 TiO2 0.09 K2O 0.72 Na2O 0.51 SO3 7.26 Loss of ignition 3.42 Insoluble residue 1.23 MANUFACTURING PROCESS OF AAC BLOCK Code Provision – IS 269:1989 and IS 383:1970
  10. 10. Production Production is a continuous process that may be envisioned as having four stages. The four stages are depicted as: 1. Raw materials 2. Molding and cutting, 3. Autoclaving, and 4. Stocking and shipping.
  11. 11. MANUFACTURING PROCESS (1-11, then A-E)
  14. 14. STEP-WISE PRODUCTION PROCESS 1. Dosing and mixing of fly ash with lime, Ordinary Portland Cement (OPC), stabilizers, and gypsum at a high dosing speed at very high accuracy. 2. Casting and rising/pre-curing of the mixture to enable the fresh mix to rise and harden to a firm green cake with the volume of the mold. 3. Tilting mold cakes with the tilt manipulator onto a cutter machine and oiling them to prevent the sticking of the green cakes for reuse. 4. Horizontal and cross-cutting of the cakes by a cutter which is equipped with the broken-wire- detection system. 5. Milling and back tilting onto a cooking frame. 6. Green separation of cut cakes by passing through the green separator to avoid sticking of cut layers during autoclaving and eliminating further mechanical separation in white state. 7. Curing with steam at a pressure of approximately 12 Bar in an autoclave system for 12 hours. 8. 8. Buffering and de-stacking of hardened cakes from the cooking frames to the packaging line for final packaging.
  15. 15. 1. RAW MATERIALS The major raw materials are, in many processes, sand and Portland cement. In place of sand, other siliceous materials such as sandstone, shale ash, fly ash, and mixtures are often used. The raw materials are used as fine powders which are normally obtained through grinding. Grinding may be done either through a wet or dry procedure. Accurately proportioned quantities of the raw materials form the mix. In many cases, a slurry of the siliceous component is made in heated water whose temperature is controlled.  The slurry is placed in a mixer into which the cement and/or lime are added. Admixtures such as surfactants and compounds for controlling the rate of cure may also be added.
  16. 16. 2. Molding and Cutting The mixture formed after adding all the materials is put into steel molds where the production of hydrogen begins and the mass expands, creating the aerated cellular structure. The expanded mass is allowed to be set to a soft cake under controlled temperature and humidity conditions. The reaction time for expansion and setting is 30 minutes to a few hours (about 1 to 4) depending upon the raw materials. After setting, the cake is cut into the dimensions of the final product using highly strung wires (piano wires) or multiple circular saws. If the final product is to be used for structural applications, steel reinforcement is placed in the mold before casting the autoclaved aerated concrete. The factory procedure allows accurate placement of the reinforcement in the molds so that the set cake may be cut into the intended dimensions without damage. The steel reinforcement is protected from corrosion, normally by coating.
  17. 17. 3. Autoclaving The third stage of the process is autoclaving whereby the aerated concrete cures to its final strength and dimensions. Autoclaving changes the physical-chemical nature of the hydrated cement materials and produces a material with lower drying shrinkage. The conditions for autoclaving vary somewhat for different proprietary products. In general, the temperature is about 356°F (180°C) at a pressure of about 1.0 - 1.2 MPa. The time varies depending on the size and density of the products and may range from about 10 to 20 hours. Storage of the uncured cake, even though moisture and warmth, for more than 2 or 3 days before autoclaving may be detrimental.
  18. 18. 4. Stocking and Shipping After the cured units are removed from the autoclave, quality assurance tests are normally conducted. Also, if desired, additional shaping through milling or related means may be carried out and a surface finish may also be applied. After autoclaving and cooling the units are ready for use without storage. If not needed immediately after production, the units are stored at the factory site and then delivered to the job site for installation.
  19. 19. CHARACTERISTICS OF AAC BLOCKS • Light in Weight • Eco Friendly • High Thermal Insulation • Lower Water Absorption • High Sound Insulation • Termite Free • High Fire Protection • High Structural savings in steel and concrete
  20. 20. Capillarity Coefficient of Thermal Expansion o Cracking Creep Density Deterioration Resistance Fire Resistance Frost Resistance Moisture Expansion and Shrinkage • The physical and mechanical properties vary over a considerable range, depending on the quantities of the raw materials used, the mix design, and curing conditions. • The properties of cellular concrete can be given as functions of bulk density and thickness. • The properties summarized are as follows: PROPERTIES OF AUTOCLAVED AERATED CONCRETE
  21. 21. Capillarity for wetting and drying out the materials. capillary suction is slow - compared with some other porous materials such as clay bricks Capillary suction takes place exclusively through the micropores in the cell walls Coefficient of Thermal Expansion coefficient of linear thermal expansion for autoclaved aerated concrete is 8 x 10^6 per °C -- compared to 12 x 10”^ per °C for dense concrete. Cracking caused by shrinkage, creep, temperature, moisture effects, or by deformation and settlement of foundations. prestress of autoclaved aerated concrete slabs, due to differential drying and cooling after autoclaving, may in some cases increase crack resistance to some extent.
  22. 22. Creep Low about the elastic deformation Factors affecting the creep of autoclaved aerated concrete are stress level, moisture content, ambient temperature, and relative humidity. Density the practical density is higher because of the moisture content and the presence of any reinforcement range of (300 - 1000 kg/m3 ), with (500 kg/m3 ) or more as the most common density for load-bearing products and reinforced flexural members. Deterioration Resistance because of its porosity and relatively low alkalinity (pH = 9 - 10.5), does not provide the same corrosion protection of reinforcement as that provided by dense concrete
  23. 23. Termite Resistance AAC is also resistant to insects, termites, and fungi. Fire Resistance non-combustible, Because of its low thermal conductivity, heat migration takes place at a lower rate than in dense concrete. gives fire resistance of 2 hours, thus increasing the fire resistance by 30 to 40 percent compared to other building materials Frost Resistance It is resistant to frost. Nevertheless, a risk of frost damage exists if the moisture content in any part of the construction unit exceeds the critical moisture content
  24. 24. Permeability varies with the moisture content of the material. It decreases with an increase in moisture content in the pores penetration can take place through improperly formed joints and other connections in the building The water vapor permeability by diffusion also decreases with an increase in the moisture content Shaping and Working can be easily cut, nailed, drilled, milled, or shaped to accommodate building needs such as utilities, or other construction requirements Sound Absorption provide good sound insulation, having sound absorption properties somewhat better than that of smooth dense concrete If the aerated concrete is painted or coated, its sound insulation effectiveness is reduced.
  25. 25. STRENGTH Strength tends to increase with an increase in density, while thermal resistance tends to increase with a decrease in density Compressive Strength increases with an increase in density decreases with an increase in the moisture content of the material. Tensile Strength The tensile strength of autoclaved aerated concrete is normally 1/4 to 1/6 of the compressive strength. (about 20 percent)
  26. 26. STRUCTURE The structure of autoclaved aerated concrete is characterized by pores or cells which are formed by the hydrogen gas, air, and water during the molding and expanding phases of productioa n If the cells are irregularly shaped rather than spherical, excessive reduction in strength occurs
  29. 29. COMPARISON AAC BLOCK • 600x200x200mm • ₹60/pc • 1m3 = 41pc • Cost - ₹2460/m3 Red Brick • 200x100x100 mm • ₹8/pc • 1m3 = 500pc • Cost - ₹4000/m3 Concrete Block • 400×200x100 mm • ₹35/pc • 1m3 = 125 pc • Cost - ₹4375/m3 (The prices are based on the rates by top suppliers of Dakshin Kannada registered on IndiaMART) 4” 7.5”
  30. 30. COMPARISON
  31. 31. AAC Blocks ◦ AAC blocks are lightweight and easy to handle ◦ Each of the AAC blocks can weigh anywhere from 3 kg to 15 kg, depending on the size of the individual blocks ◦ AAC blocks are very large in size ◦ AAC blocks are usually uniform in size and don’t come with rugged or rough edges that need to be trimmed ◦ AAC blocks are mostly used for non-load bearing purposes and used to create partition walls ◦ The construction process is relatively quicker ◦ AAC block prices are high for small quantities of production ◦ AAC blocks may need a weather-coating finish if they are exposed externally Red Bricks ◦ Red bricks come in different weights depending on the seller ◦ The average weight can range between 2-3.5 kg for one block ◦ Red bricks are smaller in size ◦ The size and shape of red bricks can be slightly different as they are mostly handmade. They also have rough edges that need trimming before use ◦ Red bricks can be used for constructing internal and external walls, structural units, and even arches and aesthetic setups ◦ The construction process is tedious and time-consuming ◦ The production cost may be cheaper for smaller production quantities ◦ The size and shape of red bricks can be slightly different as they are mostly handmade. They also have rough edges that need trimming before use COMPARISON WITH RED BRICKS
  32. 32. S.NO. DESCRIPTION AAC BLOCK CLAY BLOCK 1 Structural Cost Steel Saving Up to 15% No Saving 2 Breakage /Wastage Less than 5% Average 10 to 12 % 3 Construction speed Speedy construction Comparatively slow 4 Availability Anytime Shortage in monsoon 5 Energy Saving 30% reduction No such saving 6 Accuracy in dimension 99% 90% 7 Cost 30% cheaper than Red bricks - MANUFACTURING PROCESS OF AAC BLOCK COMPARISON WITH CLAY BLOCKS
  33. 33. Sr.No. Autoclaved Aerated Concrete Normal Aggregate Concrete 1 Autoclaved aerated concrete is a versatile lightweight construction material and usually used as blocks. Normal concrete has heavy weights compared to the AAC. 1 AAC Block size = 6 * brick size 1 AAC Block weight = 1/2 of aggregate block weight 2 A low density and excellent insulation properties due to high porosity. High density and lower insulation property 3 The low density is achieved by the formation of air voids to produce a cellular structure The concrete so formed has a high density and compact 4 Densities range from about 460 to 750 kg/ m3 Medium density concrete blocks have a typical density range of 1350-1500 kg/m3 and dense concrete blocks a range of 2300- 2500 kg/ m3 5 The finished product is up to five times the volume of the raw materials used, with an air content of 70% to 80% (depending on the required strength and density.) The finished product is compact and nonporous. 6 Easily workable – can be sawed, nailed and drilled easily even than wood. Cannot be sawed, nailed or drilled as easy as AAC blocks. 7 No curing required – labour cost is saved of curing. Curing is must. COMPARISON WITH NORMAL AGGREGATE CONCRETE
  34. 34. APPLICATIONS Internal And External walls Cavity Walls Partition Walls Air Conditioned buildings Fire-rated applications Insulated buildings
  35. 35. ADVANTAGES OF AAC BLOCKS Thermal efficiency is one of the biggest advantages of these AAC blocks. They keep the house pleasant during both summers and winters and reduce heating and cooling loads. The blocks handle fire better than traditional blocks. Individual blocks are much larger in size than clay bricks. As a result, the structure completion happens faster. For large constructions, the AAC block prices are better when compared to using burnt clay bricks. AAC blocks are environmentally friendly as no toxic materials are used to create these bricks. The production process also involves 50% lesser emission of greenhouse gases and 30% lesser creation of solid wastes.
  36. 36. ADVANTAGES OF AAC BLOCKS The porous material of AAC blocks helps absorb moisture naturally, resulting in lesser mildew, moisture, and humidity inside the house. These blocks are up to 3 times lighter in weight than traditional clay or cement blocks. The need to trim and cut AAC blocks might be more compared to traditional blocks. AAC blocks are, however, more precise. These come in perfect dimensions with no need for trimming. Since these blocks are lightweight, you will spend less on the AAC block prices when you consider transportation costs and labor charges for loading and unloading blocks. These porous and airy materials last very long and are not affected by climatic changes.
  37. 37. LIMITATIONS OF AAC BLOCKS Improper installation can cause cracks in the structure of the blocks, and this will affect the final finish of the building. AAC blocks porous material means they have to be handled carefully during loading and unloading. Also, the fact that these are lightweight may make the laborers handle them causally, causing unwanted breakage. AAC block prices vary with the quantity you order. If you are constructing a low-rise, small building, then the overall brick prices may be high when compared to traditional bricks. These are best used in high-rise buildings. Not any mason can lay AAC blocks. These need to be done only by experts. AAC blocks cannot handle heavy loads and are called non-load-bearing materials. Therefore, these should be mostly used for partition walls.
  39. 39. REFERENCES • The manufacturing process of AAC block • Research paper - AERATED AUTOCLAVED CONCRETE (AAC) BLOCKS: A REVOLUTION BUILDING MATERIAL IN THE CONSTRUCTION INDUSTRY – IJSTM • A Review of Autoclaved Aerated Concrete Products by NBSIR – US Department of Energy • Code Provision – IS 269:1989 and IS 383:1970 • Videos • • • • • • • • • • • • •