Autoclaved Aerated Concrete

Autoclaved Aerated Concrete

ABSTRACT

Aerated Autoclaved Concrete

Autoclaved Aerated Concrete ("AAC"), though relatively new to India, is currently one of the many building products which is "green" or "environmentally friendly." Autoclaved Aerated Concrete is a popular construction material for its distinctive properties such as light weight, high strength to weight ratio, low thermal conductivity and high insulation values and resistance to fire.

In multi-storied constructions, the framework and foundation of a building represents a larger part of the cost. They must carry both the live loads and dead loads of the buildings, 67% of the dead loads will be reduced with the use of Aerated Concrete due to its lightweight (0.7 T/M3). Considerable savings in the costs can be achieved in Steel (30%) and Cement 20% consumptions resulting in less expensive frame works and foundations, in addition to providing additional comforts like good sound absorption and higher thermal insulation.

The savings due to the reduced power consumptions in aerated concrete construction with air conditioning are enormous, that help in saving more than 25% of the electricity bills each month. In non air-conditioned dwellings the savings are 10% and the internal atmosphere is cooler in summer and warmer in winters. The overall savings in the construction cost could be 30% of the total cost of construction and 50% time saving in construction. The saving in interest and incidentals on time is money. The products also contribute towards pollution abatement and cleaner environment by utilizing fly ash

INTRODUCTION

The aerated concrete is a Swedish invention. In 1923 Dr Axel Eriksson at the Royal Institute of Technology in Stockholm made the first successful steam curing of cellular cement products. He combined steam cured cement and the air cured cellular cement products into a unique invention  known as Autoclaved Aerated Concrete, AAC. The first industry for production of AAC was built in Sweden in 1929, and now factories are operating all over the world.

ABOUT AAC

Autoclaved aerated concrete (AAC) is a lightweight, precast building product used around the world. Available in blocks and panels of various sizes, AAC is an ideal material for structural walls, firewalls, sound walls, floor and roof systems. 

AAC IS A GREEN CONCRETE

(AAC) is well known as an environmentally friendly construction material. AAC is manufactured from common and abundant natural raw materials and the finished product is up to twice the volume of the raw materials used, making it extremely resource-efficient and environmentally friendly. The energy consumed in the production process is only a fraction compared to the production of other materials. The manufacturing process emits no pollutants and creates no by-products or toxic waste products.

 (AAC) is a load-bearing block, which also provides thermal and sound insulation as well as fire protection, thereby eliminating the need for many different layers of materials. The workability of AAC  helps to eliminate waste on the jobsite.

AAC is completely inert and does not emit toxic gases, even when exposed to fire

OVERVIEW OF MANUFACTURING PROCESS OF AAC

Composition by weight

                                       fly ash :55%-60%                                                                                         

                                     Gypsum:2%-3%                           

                                      Cement:10%-12%         

                                            Lime:12%-14%                                                   

                    Alluminumpowder:0.03%

        

PRICE AND COSTING OF AAC

Since AAC is light weight, if you plan to use the blocks at the conceptual stage of the building, the architect / structural engineer can reduce the steel reinforcement in the structure. Mortar joints for walls built with AAC are reduced by 2/3 compared to the walls built by traditional clay bricks. The AAC blocks are big and hence you pay only for 1/3 of the mortar cost as it requires less quantity for plastering in the finishes. AAC  block is easy to cut and chisel; the electrical conduits and plumbing pipes can be easily installed and concealed in the walls. There will be 50% saving in time and labor on masonry, plumbing and electrical works. There is a scope for only 0-1% wastage of material. 

Cost of AAC

Estimate for 100 S ft of 200 mm AAC masonry wall
Particulars	Quantity	Rate/Unit(Rs)	Amount
AAC	71	98	6958
Mortar
Cement bags	1.5	225	337
Sand (Cu Ft)	6	1200	72
Plastering(20mm)
Cement bags	1	225	225
Sand (Cu Ft)	4	1200	48
Cost for 100 sft of wall			7640
Rate per sq. ft.			76.40