A Brief description on Light weight Construction Materials.

1. LIGHT WEIGHT CONSTRUCTION MATERIALS
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UNIT-1
LECTURE - 1
Brig. S.K. Sharma (Retd.)
Pro Vice Chancellor and Professor
Department of Civil Engineering,
The Northcap University, Gurgaon

2. INDEX
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 LIGHT WEIGHT CONCRETE
 FOAMED OR AERATED CONCRETE
 METHOD OF MANUFACTURE
 PROPERTIES OF LIGHTWEIGHT FOAMED
CONCRETE

3. LIGHT WEIGHT CONCRETE
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NEED FOR: The conventional cement concrete is a
heavy material having a density of 2400 kg/m3 and high
thermal conductivity. The dead weight of the structure
made up of this concrete is large compared to the imposed
load to be carried. In highrise buildings Light Weight
Concrete can save money and manpower considerably.
The improvement in thermal insulation is of great
significance to the conservation of energy. The reduction
in dead weight is normally achieved by cellular
construction by entraining large quantities of air.

4. LIGHT WEIGHT CONCRETE
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There are many advantages of having low density of
concrete. It helps in reduction of dead load, increases the
progress of building, and lowers haulage and handling
costs. The weight of a building on the foundation is an
important factor in design, particularly in the case of beams
and columns which have to carry load of floors and walls.

5. METHOD OF MANUFACTURE
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Basically the main method for making concrete light is by
the inclusion of air in concrete. This is achieved in actual
practice by three different ways:-
 By replacing the usual mineral aggregate by cellular
porous or light-weight aggregate.
 By introducing gas or air bubbles. This is known as
‘aerated concrete’.
 By omitting sand from the aggregate. This is called ‘no-
fines’ concrete.
Video YouTube, Autoclaved Aerated Concerete blocks
installation, 6:26 min
Video YouTube, Foam Concrete House, 18:23 min
Video YouTube, Shobha Home Truths Demo – Block Work, 02:55
min

6. FOAMED OR AERATED CONCRETE
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 Foamed concrete is a type of porous concrete is a
highly workable low-density material which can
incorporate up to 50 per cent entrained air. It is
generally self-leveling, self-compacting and can be
pumped.

7. METHOD OF MANUFACTURING
(Continued..)
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The traditional method of making lightweight aerated or
cellular concrete involves the addition of a gas-forming
admixture like aluminum powder to a wet mortar mix followed
by autoclave curing.
Foamed concrete is made from mechanically mixing
preformed stable foam to the slurry of cement and water.
This action incorporates small air bubbles distributed uniformly
within the mortar thereby making low density concrete. The
foam is made by a simple foaming generator where air, water,
and foaming chemicals are mixed and stable foam is formed.
Foamed (or cellular) concrete is obtained by foamed
concrete technology which is environment friendly, as there
are no waste products in its production and all the ingredients
are non-hazardous. Due to its good mechanical strength, low
thermal conductivity, simple yet highly technological processing
foam concrete has become popular as an environment friendly

8. PROPERTIES OF LIGHTWEIGHT
FOAMED CONCRETE
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1. STRENGTHS:
 Compressive strength: The compressive strength of
foamed concrete is influenced by many factors such as
density, age, moisture content, the physical and
chemical characteristics of constituent materials and mix
proportions. The increase in strength with age is virtually
linear over the first 12 months unlike dense-weight
concrete which levels out much earlier. The rate of
development of strength in foamed concrete is higher than
that in the dense weight concrete.

9. PROPERTIES OF LIGHTWEIGHT
FOAMED CONCRETE (Continued..)
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 Tensile Strength: Depending on the method of curing,
the tensile strength of foamed concrete can be as high as
0.25 times its compressive strength.
 Shear Strength: The shear strength generally varies
between 6 and 10 percent of the compressive
strength. Shear reinforcement may be required in
flooring and roofing units.

10. PROPERTIES OF LIGHTWEIGHT FOAMED
CONCRETE(Continued…)
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2. SHRINKAGE: Like all cement products, foamed
concrete shrinks during the setting stage. The shrinkage
depends upon the type and amount of cement in the mix;
water-to-cement ratio type of curing process, size of
element, quality of sand and density of foamed
concrete. The most shrinkage occurs during the first 28
days, after this time it is negligible. During the first 28 days,
if the conditions of manufacture of the foamed concrete are
well controlled, shrinkage can be kept below 0.1 per
cent.

11. PROPERTIES OF LIGHTWEIGHT FOAMED
CONCRETE(Continued…)
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3. EXPANSION: The coefficient of linear expansion for
foamed concrete is or the same order of magnitude as
for normal concrete, i.e 0.00001 per degree centigrade.
This factor becomes important in the applications where
the concrete elements are exposed to extreme heat and
cold variations, in case of large areas of roof slabs.

12. PROPERTIES OF LIGHTWEIGHT FOAMED
CONCRETE(Continued…)
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4. Acoustic insulation: Foamed concrete has a high sound
absorption capacity. In general, dense-weight concrete
tends to reflect sound whereas foamed concrete absorbs the
sound. This slight disadvantage is in most cases academic,
since most walls are either rendered, painted or both. This in
turn will make a wall reflect sound as does dense-weight
concrete.

13. PROPERTIES OF LIGHTWEIGHT FOAMED
CONCRETE(Continued…)
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5. Thermal insulation: Thermal insulation is one of the
extremely important characteristics of foamed
concrete. Due to its cellular structure, it offers a very
low transmission of heat resulting in high energy
conservation. The thermal conductivity increases with the
increase in the density of concrete. The thermal
conductivity of foam concrete is very low varying from 0.1
to 0.38.

14. PROPERTIES OF LIGHTWEIGHT FOAMED
CONCRETE(Continued…)
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6. Fire resistance: Foamed concrete is fire resistant and
thus is suited to fire rated applications. Furthermore, the
application of intense heat such as an oxy-torch held close
to the surface of foamed concrete does not make it burn,
spall or give off toxic gases, fumes or smoke as is the case
with normal dense-weight concrete. The reinforcing steel
remains cool and protected for a much longer period.

15. The Northcap University, Gurgaon15
Thank You