Unit-1 Lecture-5 - Light Weight Construction Materials by Brig. S.K. Sharma - PowerPoint PPT Presentation

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Unit-1 Lecture-5 - Light Weight Construction Materials by Brig. S.K. Sharma

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Title: Unit-1 Lecture-5 - Light Weight Construction Materials by Brig. S.K. Sharma


1
UNIT-1LECTURE - 5
  • LIGHT WEIGHT CONSTRUCTION MATERIALS
  • Brig. S.K. Sharma (Retd.)
  • Pro Vice Chancellor and Professor Department
    of Civil Engineering,
  • The Northcap University, Gurgaon

2
INDEX
  • DIFFERENT TYPES OF FIBRES
  • STEEL-FIBRE
  • POLYPROPYLENE FIBRE
  • ASBESTOS FIBRE
  • GLASS FIBRE
  • CARBON FIBRE
  • APPLICATIONS OF FIBRE REINFORCED CONCRETE (FRC)
  • BATCHING, MIXING, PLACING, COMPACTION AND
    FINISHING OF FRC

3
DIFFERENT TYPES OF FIBRES
  • Although every type of fibre has been tried out
    in cement and concrete, not all of them can be
    effectively and economically used. Each type of
    fibre has its characteristic properties and
    limitations. Some of the fibres that could be
    used are steel fibres, polypropylene, nylons,
    asbestos, coir, glass and carbon. They are
    discussed in succeeding text.

4
  • STEEL-FIBRE A number of steel-fibre types are
    available as reinforcement. Round steel fibres
    the commonly used type, and are produced by
    cutting round wires into short lengths. The
    typical diameters lie in the range of 0.25 to
    0.75 mm. Steel fibre having a rectangular cross
    section are produced by slitting the sheets about
    0.25 mm thick. For improving the mechanical bond
    between the fibre and matrix, indented, crimped,
    machined and hook-ended fibers are normally
    produced.
  • POLYPROPYLENE FIBRE Polypropylene and nylon
    fibres are found to be suitable to increase the
    impact strength. They possess very high tensile
    strength, but their low modulus of elasticity and
    higher elongation do not contribute to the
    flexural strength.

5
  • ASBESTOS FIBRE Asbestos is a mineral fibre and
    has proved to be the most successful of all
    fibres as it can be mixed with Portland cement
    paste. For unimportant fibre concrete, organic
    fibres like coir, jute, canes plits are also
    used.
  • GLASS FIBRE Glass fibre is a recent introduction
    in making fiber concrete. It has very high
    tensile strength of 1020 to 4080 N/mm2. Glass
    fibre which is originally used in conjunction
    with cement was found to be effected by alkaline
    condition of cement. Therefore, alkali-resistant
    glass fibre by trade name CEM-FIL has been
    developed and used. The alkali resistant fibre
    reinforced concrete shows considerable
    improvement in durability when compared to the
    conventional glass fibre.

6
  • CARBON FIBRE Carbon fibre perhaps posses very
    high tensile strength, say from 2110 to 2815
    N/mm2. It has been reported that cement composite
    made with carbon fibre as reinforcement will have
    high modulus of elasticity and flexural strength.
    Limited studies have shown good durability. The
    use of carbon fibres for structures like
    cladding, panels and shells have a promising
    future.

7
APPLICATIONS OF FRC
  • Fibre reinforced concrete is increasingly used on
    account of the advantages of increased static and
    dynamic tensile strength, energy absorbing
    characteristics and better fatigue strength. The
    uniform dispersion of fibres throughout the
    concrete provides isotropic properties not common
    to conventionally reinforced concrete.
  • Uses Fiber reinforced concrete has been tried on
    overlays of air-field, road pavements, industrial
    floorings, bridge decks, canal lining, explosive
    resistant structures, refractory linings etc. The
    fibre reinforced concrete can also be used for
    the fabrication of precast products like pipes,
    beams, stair case steps, wall panels, roof
    panels, manhole covers etc.

8
  • However, the main applications of SFRC are in
    highway and airfield pavements, hydraulic
    structures, tunnel linings, industrial floors,
    bridge decks, repair works etc. specifically,
    SFRC can be applied in the following areas-
  • HIGHWAY AND AIRFIELD PAVEMENTS the steel-fibre
    concrete can be used in new pavement
    constructions or in the repair of existing
    pavements by the use of bonded or unbonded
    overlays to the slab beneath. The major
    advantages are a higher flexural strength
    results in the reduction of required pavement
    thickness the resistance to impact and repeated
    loading is increased.
  • SFRC gives a smooth riding surface without
    irregular depressions. The overlays for the
    rehabilitation of runways, taxiways, bridge
    decks, and the strengthening of existing runways
    and taxiways to comply with the rigid
    requirements of the newer generation of
    heavy-duty jet aircrafts, are extensively used.
    SFRC can be advantageously used in the repair of
    damaged patches in existing runways, and highway
    pavement slab.

9
  • HYDRAULIC STRUCTURES The major advantage of
    using steel-fiber concrete in hydraulic
    structures is its resistance to cavitation or
    erosion damage by high velocity water flow. The
    steel-fiber concrete has been successfully used
    in the repair of spilling basin at Tarbela Dam in
    Paksitan. The fibre concrete contained about one
    per cent (by volume) of 25x0.25x0.55 mm slit
    steel fibres.
  • FIBRE SHOTCRETE Fibre Shotcrete fibre shotcrete
    has been used in rock slope stabilization, tunnel
    lining and bridge repair. A thin coating of plain
    shotcrete applied monolithically on top of the
    fiber shotcrete, may be used to prevent surface
    staining due to rusting.
  • PRECAST APPLICATIONS As brought out earlier they
    include manhole covers, and concrete pipes.
    Improved flexural and impact strengths may allow
    the use of steel-fibre concrete components in
    rough handling situations.

10
  • CURRENT DEVELOPMENT IN FRC
  • The following are the three new developments
    taking place in FRC-
  • High fibre volume micro-fibre systems.
  • Slurry infiltrated fibre concrete (SIFCON).
  • Compact reinforced composites.

11
BATCHING, MIXING, PLACING, COMPACTION AND
FINISHING OF FRC
  • Method The fibres are usually added to the
    aggregates before the introduction of cement and
    water into the mixer. For laboratory testing,
    fibres can be added in small amounts to the
    rotating drum charged with cement, aggregate and
    water. For large batches, the fibres are blown
    into the previously charged rotating drum.
  • A fibre mix generally requires more time and
    vibration to move the mix and to compact it into
    the forms. Surface vibration of forms and exposed
    surface is preferable to prevent segregation.

12
  • Some of the precautions taken while mixing
    placing and compacting fibre-reinforced concrete
    are as follows-
  • While mixing small quantities of fibre reinforced
    concrete by hand, there is a possibility of steel
    fibres hitting the eyes of the worker or pricking
    the hand. To avoid these hazards, the hands
    should be protected by gloves and the eye with
    safety glasses.
  • A pan mixer of the counter-flow type should be
    used for mixing fibre reinforced concrete.
  • For uniform distribution of steel fibres, a
    dispenser should be used. While dispensing the
    fibres into concrete, the rate at which the
    fibres are fed to the mixer shouldbe synchronized
    with rate of mixing.
  • _______________x________________

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