UNIT 1 Lecture 1- Light Weight Construction Materials by Brig. S.K. Sharma

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UNIT-1LECTURE - 1

• LIGHT WEIGHT CONSTRUCTION MATERIALS

• Brig. S.K. Sharma (Retd.)
• Pro Vice Chancellor and Professor Department
  of Civil Engineering,
• The Northcap University, Gurgaon

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INDEX

• LIGHT WEIGHT CONCRETE
• FOAMED OR AERATED CONCRETE
• METHOD OF MANUFACTURE
• PROPERTIES OF LIGHTWEIGHT FOAMED CONCRETE

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LIGHT WEIGHT CONCRETE

• 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.

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LIGHT WEIGHT CONCRETE

• 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.

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METHOD OF MANUFACTURE

• 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, 626 min
• Video YouTube, Foam Concrete House, 1823 min
• Video YouTube, Shobha Home Truths Demo Block
  Work, 0255 min

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FOAMED OR AERATED CONCRETE

• 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.

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METHOD OF MANUFACTURING (Continued..)
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 alternative.
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PROPERTIES OF LIGHTWEIGHT FOAMED CONCRETE

• 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.

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PROPERTIES OF LIGHTWEIGHT FOAMED CONCRETE
(Continued..)

• 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.

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PROPERTIES OF LIGHTWEIGHT FOAMED
CONCRETE(Continued)

• 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.

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PROPERTIES OF LIGHTWEIGHT FOAMED
CONCRETE(Continued)

• 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.

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PROPERTIES OF LIGHTWEIGHT FOAMED
CONCRETE(Continued)

• 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.

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PROPERTIES OF LIGHTWEIGHT FOAMED
CONCRETE(Continued)

• 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.

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PROPERTIES OF LIGHTWEIGHT FOAMED
CONCRETE(Continued)

• 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.

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• Thank You