Concrete Technology

1. SPECIAL CONCRETE

2.  Light Weight Concrete
 Self Compacting Concrete
 Fiber Reinforced Concrete
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3.  Density – 300 to 1900kg/m3 – ordinary
concrete – 2400 kg/m3.
 Usage of porous aggregates in LWC.
 Reduces DL of structures – better insulation
to heat and sound.
 Used in precast concrete and RCC units.
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4.  LWC also called low density aggregate
concrete.
 LWC made of artificial light weight aggregate
instead of crushed aggregate.
 LWA – porous, not very strong, crushed
easily.
 Higher water absorption – 5 to 20%.
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5.  DL of structure reduces.
 Lower handling costs.
 Reduces foundation cost particularly in weak soil and tall
structures.
 Greater fire resistance.
 Economical for non load bearing walls.
 Higher ductility and lower modulus of elasticity – helps in
seismic design areas.
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6.  Density – 300 to 1900kg/m3.
 Workability – Due to low density and porous
aggregates – workability needs special attention.
 Unit Weight – LWC weighs b/w 16 to 17.6
kN/m3.
 Strength – LWC strength b/w 0.3 to 40 Mpa.
 Abrasion resistance - Abrasion of LWA increases
with compressive test.
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7.  Thermal properties – Thermal insulation – 3 times
greater than bricks and 10 times greater than normal
concrete.
 LWC is more fire resistant than normal concrete.
 LWC having lower sound insulation compare to
normal concrete.
 Durability of LWC is lesser compare to ordinary
concrete.
 LWC elements can be repaired easily and economical
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8.  LWA Concrete
 Aerated Concrete
 No-fines Concrete
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10.  Prepared – porous, LWA of low specific gravity
of 2.6.
 Natural LWA – Pumice, Rice husk, Saw dust
etc.
 Artificial LWA – Expanded clay, slate, shale,
foamed slag.
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11.  Reduce DL of concrete structure, reduces
column, footing and other load bearing
element size.
 Ideal for roof deck repairs elevated floor slabs
etc.
 LWA aggregates have higher insulation.
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12.  Prepared by inducing air or gas into fresh
concrete.
 Called as ‘Gas Concrete’ or ‘Foam Concrete’
or ‘Cellular Concrete’.
 May or may not contain coarse aggregates.
 Lower density grades used – insulation
purposes
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13.  Medium density grades – building blocks,
load bearing walls.
 Higher density grades – prefabricated
structural members.
 Aerated Concrete – Aluminum powder, Stable
foam, expansive solid matter.
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14.  Load bearing walls.
 Partition walls in buildings.
 Floor panels.
 Insulation cladding to exterior walls
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15.  It consists of cement, coarse aggregate and water
only.
 Absence of fine aggregates – voids created –
concrete is light weight.
 Void content – 30 to 40%
 W/R ratio – 0.38 to 0.5
 Bond Strength – very low – no reinforcement is
used
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16.  Housing work
 Temporary structures
 NFC – used as heat insulator for external walls.
 NFC is popular where sand is not available.
 Used in casting building blocks.
 Used as pavement material – parking lots, tennis
courts etc.
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17.  Self compacting concrete is also called as
High performance concrete.
 SCC is a high fluidity concrete – easily placed
and self consolidated due to its own gravity.
 Slump – 200 to 250 mm.
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18.  SCC introduced by Okamura in 1988 in
Japan.
 SCC reduced – construction time – 2.5 years
to 2 years for anchorages.
 SCC – useful – areas of congested
reinforcement.
 Purpose of SCC – decrease risk due to human
factor – enable economic efficiency.
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19. Concrete that is able to flow and consolidate
under its own weight, completely fill the
formwork in the presence of dense
reinforcement, while maintaining homogeneity
and without the need for any additional
compaction.
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20.  OPC – 43 and 53 grade used
 CA – size 12- 20mm, well graded cubical or
rounded, uniform grading and shape
 FA – Natural or manufactured
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