Structural Lightweight Concrete

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Structural Lightweight Concrete
Abbas Jamani (SD0510) CEPT University , Ahmedabad
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Contents

• Introduction
• Properties of LWC
• Applications of LWC
• Advantages and disadvantages
• Case study
• conclusion
• References

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Introduction

• Lightweight concrete can be defined as a type a
  type of concrete which includes an expanding
  agent in that it increases the volume of the
  mixture while giving additional qualities and
  lessened the dead weight.
• It is lighter than the conventional concrete.
• The use of lightweight concrete has been
  widely spread across countries such as USA,
  United Kingdom and Sweden.

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• It was first introduced by the Romans in the
  second century where The Pantheon has been
  constructed using pumice, the most common type of
  aggregate used.
• The building of The Pantheon of lightweight
  concrete material is still standing eminently in
  Rome until now for about 18 centuries as shown in
  Figure . It shows that the lighter materials can
  be used in concrete .

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The Pantheon
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Compressive Strength

• Compressive strength is the primary physical
  property of concrete and is the one most used in
  design.
• Fourteen trial mixes had been prepared
• during the research and from the results, the
  mixture with the highest compressive strength was
  used.

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Compressive strength at different densities
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Compressive strength at different percentage of
foam
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Compressive strength at different w/c ratio
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Compressive strength at 28 days
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Compressive strength for different of foam
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Compressive strength at different w/c ratio
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Water Absorption

• Water absorption is an important factor due to
  the porous structure of the aerated
• lightweight concrete.
• The water absorption test is done using the
  samples prepared at the age of 28 days.
• The purpose of this test is to identify the
  capability of the concrete to absorb water.

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Water absorption at different percentage of foam
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Water absorption at different foam agent and
water ratio
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Moisture content at different percentage of foam
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Density of wet and hardened concrete
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Entrained Air

• As with normal-weight concrete, entrained air in
  structural lightweight concrete ensures
  resistance to freezing and thawing and to deicer
  applications.
• It also improves workability, reduces bleeding
  and segregation, and may compensate
• for minor grading deficiencies in the
  aggregate.

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• The amount of entrained air should be sufficient
  to provide good workability to the plastic
  concrete and adequate freeze-thaw resistance to
  the hardened concrete.
• Air contents are generally between 5 and 8,
  depending on the maximum size of coarse aggregate
  used and the exposure conditions.

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SLUMP

• Due to lower aggregate density, structural
  lightweight concrete does not slump as much as
  normal-weight concrete with the same workability.
• It is seldom necessary to exceed slumps of 125 mm
  (5 in.) for normal placement of structural
  lightweight concrete.

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VIBRATION

• As with normal-weight concrete, vibration can be
  used effectively to consolidate lightweight
  concrete the same frequencies commonly used for
  normal-density concrete
• are recommended.
• Excessive vibration causes segregation by forcing
  large aggregate particles to the surface.

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THERMAL RESISTANCE
Thermal resistance of concrete vs density
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APPLICATIONS

• Lightweight concrete has been used since the
  eighteen centuries by the Romans.
• The lightweight concrete was also used in
• construction during the First World War. The
  United States used mainly for shipbuilding.
• It is widely used as loose-fill insulation in
  masonry construction where it enhances fire
• ratings, reduces noise transmission, does not
  rot and termite resistant.

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• It is also used for vessels, roof decks and other
  applications.

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ADVANTAGES

• Rapid and relatively simple construction.
• Economical in terms of transportation as well as
  reduction in manpower.
• Significant reduction of overall weight results
  in saving structural frames, footing or piles.
• Most of lightweight concrete have better nailing
  and sawing properties than heavier and stronger
  conventional concrete.

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DISADVANTAGES

• Very sensitive with water content in the
  mixtures.
• Difficult to place and finish because of the
  porosity and angularity of the aggregate.
• Mixing time is longer than conventional concrete
  to assure proper mixing.

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CASE STUDY

• Wellington stadium.
• Location New Zealand.
• Capacity of the stadium 40000
• Architects Hok-Lobb (brisbane), Warren
  Mahoney.
• Structure consultants Holmes Consulting Group
• Contractor Fletcher Construction, Ltd.
• LWA Supplier TXI -Pacific Custom Materials, Inc.
  (California).

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History And Layout

• The stadium is sited in a prominent location on
  the harbour edge, in close proximity to the main
  Wellington railway station, the Parliament
  buildings.
• The site is exposed to wind blown sea spray and
  is located just a few hundred metres from one of
  the country's most active and violent
• seismic fault lines.

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• The structural layout consists of an oval bowl
  around the playing field (roofed only over the
  spectator seating) and is connected by a two
  level open walkway and parking building to the
  railway station.
• At the southern end of the oval there is a
  four-storey administration building that also
  forms part of the main stand .

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The completed stadium
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FACTORS FAVOURING

• Poor foundation condition.
• Severe earthquake forces.
• Durability.
• Rapid construction.
• Space utilization.
• Reduced site work.
• Innovative spirit.

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DESIGN

• The use of lightweight concrete was initially
  proposed by Stresscrete, the precast concrete
  supplier.
• But it was also readily accepted by the project
  structural consultants, Holmes Consulting Group,
  who were impressed by the potential of the
  product to reduce cost and responded
  enthusiastically to the challenge of a new
  material.

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• In the final analysis, the choice was between a
  structure of lightweight concrete, or one of
  steel. Normal weight concrete was ruled out early
  in the final design process.

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Properties

• Compressive strength 44 MPa.
• Density 1845 kg/m3.
• Modulus Of Elasticity 19 GPa.
• Creep 2.3.

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CONCLUSION

• The initial findings have shown that the
  lightweight concrete has a desirable strength to
  be an alternative construction material for the
  industrialized building system.
• The strength of aerated lightweight concrete are
  low for lower density mixture. This resulted in
  the increment of voids throughout the sample
  caused by the foam.

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• The foamed lightweight concrete is not suitable
  to be used as non-load bearing as the compressive
  strength is 27 less than recommended. The
  compressive strength is accepted to be produced
  as non-load bearing structure.

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References

• Report on research project on lightweight
  concrete.
• Formed Lightweight Concrete. www.pearliteconcretef
  orrorepair.com
• A.M Neville (1985)
• Properties of concrete
• Cellular Lightweight Concrete, Plan City/NCS LLC.
  
• www. Neoporsystem.com

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• Thank you