Light weight concrete



Advantages of light weight concrete

         Reduction in weight on foundation
         Low thermal conductivity
         Use of industrial waste
         Low haulage and handling cost
         Increase in the speed of construction


Method of production
No fine concrete
Light weight aggregate concrete
Aerated concrete
Chemical aerating
Foaming mixture
a) Gravel
b) Crushed stone
c) Coarse clinker
d) Sintered
    pulverized ash
e) Expanded clay
    or shale
f) Expanded slate
g) Foamed slag
a) Clinker
b) Foamed slag
c) Expanded clay
    or shale
d) Expanded slate
e) Sintered    
    pulverized ash
f) Exfoliated 
   vermiculite
g) Pumice
h) Expanded 
    perlite
a) Aluminum
    powder method
b) Hydrogen
    peroxide and  
    bleaching powder
    method
a) Performed foam
b) Air entrained
    foam


Light weight aggregate concrete
Natural

1.     Pumice
2.     Diatomite
3.     Scoria
4.     Volcanic cinders
5.     Saw dust
6.     Rice husk

Artificial

1.     Artificial cinders, Coke breeze
2.     Foamed slag
3.     Bloated clay
4.     Brick bats
5.     Sintered fly ash
6.     Exfoliated vermiculite
7.     Expanded perlite


Properties of light weight aggregate concrete

         Density
         Strength
         Workability
         High and rapidly absorption quality
         Permeability
         Durability
         Thermal conductivity


Typical properties of light weight concrete
Type of concrete
Density of aggregate in Kg/m3
Mix proportion by volume cement: aggregate
Dry density of concrete in Kg/m3
Compressive strength in N/mm2
Foamed slag
900
1:8
1:6
1700
1850
7
21
Expanded clay
100
1:11
1:6
650-1000
1100
3-4
14
Expanded slate
950
1:6
1:4.5
1700
1750
28
35
Sintered fly ash
1050
1:6
1:4.5
1:3.5
1450
1500
1550
28
36
41
Pumice
500-800
1:6
1:4
1:2
1200
1250
1450
14
19
29
Exfoliated vermiculite
65-130
1:6
300-500
2


Aerated concrete

         By formation of gas by chemical reaction within the mass during liquid or plastic state
         By mixing preformed stable foam with slurry
         By adding aluminium powder or hydrogen peroxide and bleaching powder
         Density 300 to 800 Kg/m3
         Prefabricated structures and making concrete blocks for load bearing wall.


No Fine concrete

         Aggregate cement ratio 6:1 to 10:1
         W/C ratio 0.38 to 0.52
         Density 1600 to 1900 Kg/m3
         Compressive strength varies from 2 to 14 N/mm2
         Very low bond strength
         Easy compaction
         Drying shrinkage is low
         Low thermal conductivity



Pervious Concrete Pavements

         Pervious concrete pavement is a unique and effective means to meet growing environmental demands.
         Pervious concrete is a mixture of Portland cement, Coarse aggregates, water. sand is not added.
         Pervious concrete mass consists of an interconnected void structure. This allows water to seep through at very high speeds.
         As there is no fine aggregate, void space is between 15-30%.


Ferro cement

         0.5 to 2.5 mm dia wire mesh at 6 to 75 mm spacing
         Cement sand ratio 1:2 to 1:3
         W/C ratio 0.4 to 0.45
         Thickness 20 to 30 mm with cover of about 2 to 5 mm
         Steel content 350 to 500 Kg/m3 of concrete
         Saving in cement and steel
         Simplicity in construction
         Lesser dead weight of materials
         High tensile strength
         Less crack width as compared to CCC
         Easy reparirability
         Non corrosive nature and easier mouldability




Ferro cement and RCC members


Casting techniques

         Hand plastering
         Semi mechanized process ( Using hand plastering over form)
         Centrifuging
         Guniting
         Overhead water tank
         Gas holder tanks in Gobber gas plants
         Boat building
         Manhole cover
         Prefabricated roofs
         Pressure pipes
         Curved benches for parks garden and open air cinema theatre
         Tree guards



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