LIGHT WEIGHT CONCRETE

It is the type of special concrete whose density is very much lower than the conventional concrete.
The density of light weight concrete varies from 300 to 1850 kg/m3.

Methods adopted to obtain light weight concrete.

1) Replacing the natural aggregates with light weight aggregates : Here the concrete is made light weight by replacing conventional aggregates with light weight aggregates of less specific gravity.Aggregates used may be of natural or artificial in occurrence.

Natural aggregates:Pumice,Scoria ,Dolomite etc...

Artificial Aggregates:Expanded shale,Brick bats,Expanded perlite etc...

2) Aerated Concrete: Intrusion of gas bubbles in the concrete.

a) Method 1: By mixing preformed stable foam with concrete slurry

b) Method 2:i) Finely powdered Al or Zn is added to the slurry.

                    ii)This powder further reacts with calcium hydroxide,which is formed during hydration                             reaction of concrete.

                   iii) Further hydrogen is liberated by forming the cellular structure of concrete.

3) No fines Concrete: Fine aggregate fraction is totally eliminated in the concrete.Further the concrete in this state contains only cement and coarse aggregates along with certain amount of water.

Advantages of light weight concrete:

1) Due to low density self weight of the structure is reduced.

2) Easy to handle and reduces the cost of handling and transporting.

3) Possess high degree of fire resistance.

4) Possess high durability.

5) High resistance to freezing and thawing.

6) Reduced cost of transportation and placement.

7) Improves more workability.

8) Low tendency to shrinkage cracking.

Disadvantages of light weight concrete:

1) High degree of porosity.

2) Since porosity is high water requirement is more.

3) Mixing time is more than conventional concrete.

4) Difficult to place and finish.

Application of light weight concrete:

1) Bridge Decks.

2) Precast Elements.

3) Heat insulation on roofs.

4) Partition walls

5) Insulation of water pipes.

6) Fire and corrosion protection.