Autoclaved Aerated Concrete Block and its Application Aspects

Presented by :

Rajdeep Chowdhury, Biltech Building Elements Ltd.

Biltech AAC Plants

Bhigwan-Maharashtra 1,50,000 cu.m.

Bhigwan-Maharashtra 1,50,000 cu.m.

Surat – Kosamba-Gujarat 1,50,000 cu.m.

Palwal-Haryana 2,50,000 cu.m

Budge Budge – Kolkatta W.B. 2,50,000 cu.m.

WHAT IS AUTOCLAVED AERATED CONCRETE

Autoclaved Aerated Concrete (AAC) is formed by a chemical reaction between finely divided calcareous and siliceous material.

AAC has been around for over 80 years. The first documented attempt at autoclaving aerated concrete was in 1923 in Sweden by an architectural science lecturer, Dr Johan Axel Eriksson. Since then, AAC has been used extensively in Europe, Asia & USA.

Microscopic view of the crystalline composition of AAC at the cellular level.

BILTECH -AAC BLOCK & DIMENSION

LENGTH (MM) HEIGHT(MM) THICKNESS(MM)

625 240 , 250 100 to 300 (@ 25 mm)

BIS -2185(Part-III) : Specification of material

BIS- 6041 : Construction of AAC masonry

BIS- 6441 (Part I-IX) : Testing Procedure.

B.I.S.CODES APPLICABLE TO AAC BLOCK

Density (Oven Dry) Compressive Strength Thermal Conductivity ( K Value) Resistant to Fire Drying Shrinkage

551-650 Kg/Cum Minimum 30 Kg/cm2 0.162 W/mK (Average) 2 - 6 hrs depending upon Thk. 0.1 %

PROPERTIES OF AAC BLOCK

OVERVIEW OF MANUFACTURING PROCESS & PLANT

MANUFACTURING PROCESS

Plant & Machineries used in manufacturing of AAC

Mould filled with raw material De moulding Horizontal cutting

Vertical Cutting Autoclaving Blocks at stock yard

Plant & Machineries

Composition by weight :

• Fly Ash 55-60%

• Gypsum 2-3%

• Cement 10-12%

• Lime 12-14%

• Aluminum Powder 0.03%

• Balance Slurry solids generated during process

RAW MATERIALS IN AAC

RATIONALE OF USING AAC

IMPORTANT FEATURES OF AAC

•Lighter Weight

•Thermal Insulation

•Fire Resistance

•Behavior of AAC during earthquake

DENSITY OF AAC vis-à-vis OTHER WALLING MATERIAL

0

500

1000

1500

2000

2500

3000

AAC HOLLOW BLOCK

CEMENT CONCRETE

BLOCK

CLAY BRICK CONCRTE

DENSITY IN KG/CUM

Thermal Insulation

Energy savings in the operation of buildings are of particular importance as the cost of energy for heating and air conditioning in most cases represent the major cost factor in the operating cost of a building. The entrained air in the cellular structure of BILTEC AAC system gives the product excellent thermal insulation properties, as well as good heat retention characteristics. These characteristics contribute significantly to the energy saving performance of the building .

Fire resistance

AAC has one of the highest hourly fire resistance ratings per millimetre of any building material. This makes it an ideal choice for fire protection around steel columns and steel beams, and in the construction of shaft walls, stairwells, corridors and firewalls. A 100mm and a 200 mm non-load bearing wall shall have fir resistance of 2 hours and 6 hours respectively .

Behavior in Earthquake

AAC has been used for many years in areas subject to seismic action. Building which consist fully or partly of AAC have in general terms shown good resistance to earthquake forces in practice. The light weight of AAC reduces the seismic forces in common with some other materials. The non combustible and fire resistance nature of the AAC material is an advantage against fires commonly associated with earthquakes. The low weight of AAC in relation to its strength is an intrinsic advantage for earthquake design. AAC permits the designer to reduce the mass of the structure, limiting the impact of accelerations introduced in seismic situation.

Biltech QA POLICY

DNV Certificate

Biltech supports Green Building movement

BIS Codes

WORKABILTY IN AAC BLOCK

LAYING OF AAC BLOCK MASONRY

•The jointing mortar shall be leaner i.e. 1:6 cement sand mortar. Premix polymer based mortars of standard make like Ferrous crete, Weber etc may also be used. The mortar shall not be spread so much ahead of the actual laying of the units that it tends to stiffen and lose it’s plasticity there by resulting in poor bond.

•Consistency as per requirement of site must be maintained at the point of laying over bed.

•Laying of AAC block masonry shall be in accordance with the recommendations of IS 6041 of 1985 and IS 1905 of 1987. The maximum joint thickness (Vertical and Horizontal) shall be 10-12 mm.

Broad Application guideline

•The laying of block may be started either at the corners first or it may be started from one end and proceed to the other direction.

•Lay 10 mm thick cement mortar uniformly over bed. Wet the blocks on all sides by using a tray filled with 20/25 mm water and place them one by one and press it firmly to have proper bond. Ensure proper spread of mortar in the joints between the blocks.

•The first course of the cellular block masonry shall be laid with great care, making sure that it is properly aligned, leveled and plumbed, as this may assist the mason in laying succeeding courses to obtain a straight and truly vertical wall.

•Ensure all the surfaces of the block which comes in contact with cement mortar are wet to have proper bonding.

•To maintain proper cement mortar filling at the sill level, please check the height of masonry and distribute the same along the joints and if the gap is more same can be adjusted in the bedding mortar. Later the joint shall be ideally filled up with jute strips dipped in cement slurry so that flexible joint can be maintained at that level.

•Before laying the mortar, two 10 mm square rods can be placed on both the sides of the block to obtain uniform joint.

•The mortar joint shall be struck off flush with wall surface and when the mortar stiffening, it shall be compressed tightly.

•Once the masonry erected the curing shall be minimum unlike brick masonry. The curing requires more at the joints.

•Maximum erection of 5-6 courses is desirable in a day.

•Before plastering, cement slurry may be applied on the walls and only leaner mix shall be applied. The thickness shall be 10-12 mm in the external walls and in the internal application in case of dry walls plastering can be avoided. In such case directly P.O.P / Gypsum plaster can also be applied.

•Chasing and cutting

•Blocks shall be cut with a saw.

•Where ever chasing to be done in AAC Blocks, rotary cutters to be used. The chases shall be refilled with leaner mortar and chicken mesh (as per Consultants recommendation) shall be applied on the area.

All other structural requirements like placing of joint reinforcement, nominal band beams etc. Is to be considered in accordance with the recommendations laid down in I.S. Codes- 6041 & 1905

Use of Polymer based mortar for joining AAC

Thin Bed Mortar provides :

• High water Retention capability

• Self curing mortar

• Thin section application like thin set adhesives

• High bond strength, compressive strength

• Useful as an adhesive for installation of tiles on AAC Blocks directly.

• Ability to work under high temperature, humidity and stressful condition.

PU Anchors used for Cladding

TOOLS & CUTTERS FOR AAC BLOCK MASONRY

Wall Ties

Door Frame Fixing with PU Foam

PU Foams can be used for fixing Door and Window Frames. All our PU foams contain CFC-free propellants, which are completely harmless to the ozone layer

AAC BLOCK CUTTING NAILABILITY IN AAC BLOCK

DOOR FRAME FIXING CONDUITING

AAC BLOCK LAYING

Finishing in masonry

Typical detailing in AAC Block Masonry

Typical detailing

CONTACT ADDRESS :

BILTECH BUILDING ELEMENTS LTD. 232-B,GROUND FLOOR,

OKHLA INDUSTRIAL ESTATE, PHASE-III, NEW DELHI-110020

H:- +91-9811076657 |L :- 011-49696629

W :-WWW.BILTECHINDIA.COM

Thank You