4. INTRODUCTION
Lightweight concrete is concrete with an air
dried unit weight not exceeding 1850kg/m3
Aerated concrete, no fines concrete and
lightweight aggregate concrete can be
categorized as lightweight concrete.
There is another type of concrete that can be
classified lightweight concrete that is structural
lightweight concrete.
5. The primary advantage of lightweight concrete
is its low density, which reduces the loads on
foundation and supporting structures to two-
thirds or less.
The engineering properties of lightweight
concretes depend to a large extent on the
materials used in mix design.
6. Among the benefits of using lightweight
concrete are:
a) it exhibits relatively high thermal insulating
value
b) it compressive strength is low compared to
normal weight concrete of similar mix
proportions
c)it has higher drying shrinkage and higher
creep than normal weight concrete
d)Its modulus of elasticity is lower compared
normal weight concrete.|
e)It has higher absorption
7. Aerated Concrete
Well known among contractor in Europe due
to it lightness and versatility compared to
normal concrete.
It consists of cement or sand mortar with gas
being introduced inside this mix either
chemically or by using foaming agents.
Can be used for structural or non-structural
purpose
8. Elimination of coarse aggregate from the mix
and formation of a large number of voids
within the internal structure decrease the
density of the material.
The high porosity within the concrete lowers
the density
Can either formed insitu or precast
Application of autoclave curing method gives
a stronger product and better dimensional
stability than non autoclave curing one.
9. ADVANTAGE OF AUTOCLAVE
CURING
At least doubling the compressive strength
Improving long-term drying shrinkage
Having insulation property similar to timber
but much greater fire resistance.
Providing low thermal conductivity of about
10 times lower than normal concrete
Giving an attractive light gray or near white
color, although it may be covered in buildings
or structures.
10. The drawbacks of non autoclave aerated
concrete compared to normal concrete in terms
of lower strength, higher moisture content and
higher shrinkage can be solved.
11. Types of Aerated concrete
Based on the method formation, it can be divided
to two types that is:
Gas concrete or also known as aerated concrete
- Produced using gas-forming materials
(Aluminium powder, hydrogen peroxide etc)
Foamed concrete
- Produced using foaming agent
12. Gas Concrete
It is a mixture of very fine aggregates, water,
and cement with final addition of pore-forming
chemical that produces air-voids within the
aqueous mix at atmospheric pressure, causing
it to expand to certain extent depending on the
amount of gas produced inside the structure.
Aluminium powder is the most commonly
used aerating agent in gas concrete production
14. Density and Strength
Various density from 300 to 1800kg/m3 in
comparison with 2300 kg/m3 for conventional
concrete.
Lower strength & density than normal concrete
Increase in density lead to strength
improvement of the aerated concrete
Properties of this concrete differ according to
the mix proportions and the manufacturing
methods
15. Advantages
Low density lead to more economical design
Save material utilization and reduce cost
Can be cut and sawn like timber
Versatile, easier renovation work can be done
Non-combustible, fire resistance
Good sound insulation
Contribute to low construction cost and
simpler construction task in a shorter period.
Applicable for non - structural purpose
28. Voids can be seen on the surface of aerated concrete
29. Voids can be seen on the surface of aerated concrete
30. Making Of Aerated Concrete
Use cement with good quality, so that cement
particles are able to react as expected in the mix.
Water or aggregates containing impurities need
to be avoided
Any kind of fine aggregate passing 75 µm BS
sieve is allowed such as finely ground natural
fine aggregate, fine lightweight aggregate, raw
PFA, ground slag, burnt shales and others with
sometimes fine aggregate (5mm down) is added.
31. Mixing Procedure
Dry mix all the ingredient & add water finally.
Aluminium powder in the mix would react
with hydroxide of calcium or alkalis from the
cement producing hydrogen bubbles, and that
will expand the mix.
The mixture would begin to rise and fill out
the mold once the hydrogen gas is set free to
eventually create pores in the mix.
Basically, the formation of air bubbles causes
the concrete to be lightweight.
38. Some part of the structures constructed using AAC
39. Aerated Conrete In Malaysia
Still new in Malaysian construction industry
Mostly, this material has been imported from
other countries to be used here and expensive.
However, Malaysian researchers try to reduce
cost by integrating industrial waste as one of the
mixing ingredient of this material.
40. FOAMED CONCRETE
It’s a mortar mix containing air voids produced
by adding foaming agents which plays the role
of creating pores within the concrete without
chemically reacting with the cement.
Detergents, resin soap, glue resins and saponin
are some of the foaming agents used.
It is a highly workable, low-density material
which can incorporate up to 50% entrained air.
44. Advantages
This concrete which produced from the mix of
cement, fine sand and prefoamed foam has a
low density such as 400 - 1600kg/m3 .
It is generally self-leveling, self-compacting
and may be pumped.
Cost saving, fast completion and easy
application compared to steel and timber.
Foamed concrete is characterized by its low
compressive strength and high insulation
against heat and sound.
45. Making of Foamed Concrete
Determine the required parameter such as
density and compressive strength.
Then, make a cement slurry or a sandcement
slurry that is appropriate for the mix design.
The cement used for the slurry is usually Type
1 Portland Cement although other cements can
be used.
Other ingredients such as Pulverized Fuel Ash
(PFA) can also be used.
46. The w/c ratio of the slurry is usually between
0.5 and 0.6.
The mortar slurry is then transported to site,
and the foam is added there, and not at the
batching plant.
The foam is made from a concentrated
Foaming Agent using foam generator.
The bubbles are stable and able to resist the
physical and chemical forces imposed during
mixing, placing & hardening of the foamed
concrete
47. Application
Widely used in civil engineering work
Can be used in almost every parts of building
from the superstructure to the substructure,
including wall panels and roofing.
Any conventional panels or masonry units
used for load and non-load bearing walls using
normal concrete can be replaced directly by
foamed concrete panels and units.
48. Very low density foamed concrete can be used
as thermal and sound insulation panels,
filtering media and floating blocks for fishery
purposes.
Foamed concrete is ideal for filling redundant
voids such as disused fuel tanks, sewer
systems, pipelines, and culverts - particularly
where access is difficult.
Can be used for house, foundations and fire
protection, utilizing its high thermal insulation
capacity to geotechnical, highway, bridge
abutment and backfill uses
49. Foamed concrete can also be used to cast
elements for architectural purposes, pottery,
void filling, foundation raising and swimming
pool.
In highway construction, foamed concrete can
be applied as soil filling for sub-base, bridge
abutments and bridge embankment.
It is a recognised medium for the reinstatement
of temporary road trenches.
