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CHAPTER 1
Introduction
1.1 HISTORICAL PERSPECTIVE
Aerated concrete was first developed as a lightweight material consisting
of combinations of cement and quicklime silica sand, slag, pulverized fly ash, or
other siliceous fine aggregates, in the form of a fine powder. The powder is mixed
with water to form a slurry, and air or other gas (usually hydrogen) is introduced
into the slurry. Due to initial hydration of the cement, accelerated by the heat
produced by the quicklime, the mixture sets, acquiring a uniform cellular structure
(CEB, 1978).
In the early 1920s Dr. Axel Eriksson, then Assistant Professor for
Building Techniques at the Royal Institute of Technology in Stockholm, invented
an aerated concrete that he called “gas concrete.” This new material was later
called Autoclaved Aerated Concrete (AAC); its industrial manufacture was
developed in Sweden in 1929 as a combination of the technique for producing a
cellular concrete by the introduction of a gas-forming agent, and the technique for
hardening concrete through autoclaving (RILEM, 1992). AAC is usually factory
produced, high-pressure steam-cured, and available for used in pre-cast units for
floors, walls, roofs and lintels. The density of AAC is 25 to 60 pcf (3.94 E-06 to
9.45 E-06 N/mm 3 ).
From 1929, it took another 10 to 20 years until reinforced AAC elements
were developed and first used mainly in Scandinavia as roof and floor units and
wall panels. The Second World War temporarily halted the expansion in the use
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