Structural lightweight concrete


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    Failure On Expansive Soils
  • Structural lightweight concrete

    1. 1. Structural Lightweight Concrete
    2. 2. Contents  Introduction  Properties of LWC  Applications of LWC  Advantages and disadvantages  Case study  conclusion  References
    3. 3. 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. Structural lightweight concrete
    4. 4. continue….  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 . Structural lightweight concrete
    5. 5. continue… structural lightweight concrete The Pantheon
    6. 6. 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. Structural lightweight concrete
    7. 7. continue…. Structural lightweight concrete Compressive strength at different densities
    8. 8. continue…. Structural lightweight concrete Compressive strength at different percentage of foam
    9. 9. continue… Structural lightweight concrete Compressive strength at different w/c ratio
    10. 10. continue… Structural lightweight concrete Compressive strength at 28 days
    11. 11. continue… Structural lightweight concrete Compressive strength for different % of foam
    12. 12. continue…. Structural lightweight concrete Compressive strength at different w/c ratio
    13. 13. continue…. Structural lightweight concrete
    14. 14. 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. Structural lightweight concrete
    15. 15. continue… Structural lightweight concrete Water absorption at different percentage of foam
    16. 16. continue…. structural lightweight concrete Water absorption at different foam agent and water ratio
    17. 17. continue…. Structural lightweight concrete Moisture content at different percentage of foam
    18. 18. continue…. Structural lightweight concrete Density of wet and hardened concrete
    19. 19. 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. Structural lightweight concrete
    20. 20. continue…  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. Structural lightweight concrete
    21. 21. 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. Structural lightweight concrete
    22. 22. 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. Structural lightweight concrete
    23. 23. THERMAL RESISTANCE Structural lightweight concrete Thermal resistance of concrete vs density
    24. 24. 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. Structural lightweight concrete
    25. 25. continue…  It is also used for vessels, roof decks and other applications. Structural lightweight concrete
    26. 26. ADVANTAGES Structural lightweight concrete  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.
    27. 27. 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. Structural lightweight concrete
    28. 28. 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). Structural lightweight concrete
    29. 29. 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. Structural lightweight concrete
    30. 30. continue….  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 . Structural lightweight concrete
    31. 31. continue…. Structural lightweight concrete The completed stadium
    32. 32. FACTORS FAVOURING  Poor foundation condition.  Severe earthquake forces.  Durability.  Rapid construction.  Space utilization.  Reduced site work.  Innovative spirit. Structural lightweight concrete
    33. 33. 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. Structural lightweight concrete
    34. 34. continue….  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. Structural lightweight concrete
    35. 35. continue… Structural lightweight concrete
    36. 36. Properties  Compressive strength : 44 MPa.  Density : 1845 kg/m^3.  Modulus Of Elasticity : 19 GPa.  Creep : 2.3.
    37. 37. 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. Structural lightweight concrete
    38. 38. continue….  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. Structural lightweight concrete
    39. 39. Structural lightweight concrete References  Report on research project on lightweight concrete.  Formed Lightweight Concrete.  A.M Neville (1985) Properties of concrete  Cellular Lightweight Concrete, Plan City/NCS LLC. www.
    40. 40. Thank you