Lightweight concrete has a lower density than ordinary concrete due to the use of lightweight aggregates. It has strengths between 7-40 MPa, improved workability, thermal insulation, and water absorption. Lightweight concrete exhibits higher moisture movement and fire resistance compared to ordinary concrete. It is used in prestressed concrete, high-rise buildings, and to reduce dead load. While more expensive, it allows for rapid, simple construction and reduced transportation costs.

2. LIGHT WEIGHT CONCRETE
 The concrete which has considerably lower mass per unit volume than the
ordinary concrete is called light weight concrete .
 It is often made by the use of light weight aggregates due to which it is
also known as light weight aggregate concrete.

3. CHARACTERISTICS
 Density : 240 - 1820 kg/m^3
 Strength : 7 - 40 MPa
 Satisfactory durability
 Improved workability
 Good thermal insulation
 Better water absorption

4. COMPARISON WITH
ORDINARY CONCRETE
 Exhibits higher moisture movement as compared to ordinary
concrete.
 Coefficient of thermal expansion is generally much lower than
ordinary concrete .
 Exhibits higher fire resistance property than the ordinary
concrete .
 Better resistance to freeze and thaw .
 Expensive than ordinary concrete .

5. USES
This type of concrete is used in applications such as :
 prestressed concrete .
 high rise buildings .
 where extra load is not applied .
 to reduce dead load .
 for sound proofing .

6. ADVANTAGES
 Rapid and relatively simple construction .
 Economical in terms of transportation .
 Significant reduction in overall weight results in saving
structural frames , footing or piles .
 Most of the light weight concrete have better nailing and
sawing properties .

7. DISADVANTAGES
 Very sensitive with water content in the mixture .
 Difficult to place and finish because of the porosity and
angularity of the aggregate .
 In some mixes the cement mortar may separate the aggregate
and float towards the surface .
 Mixing time is longer than conventional concrete to assure
proper mixing .

8. AIR ENTRAINED
CONCRETE

9. PREPARATION
 It is prepared by adding the air entraining admixture.
 Air entraining agents / admixtures are used for the purpose
of making entrained air in concrete.
 Due to entrained air , bubbles having diameter ranges from
10 to 1000 micrometers are produced .

10. FUNCTIONS
Air entrainment in concrete performs the following functions :
 It lowers the surface tension of water and thus bubbles are created.
 Secondly the air entraining agents prevents fusing of bubbles.

11. METHODS OF
PRODUCING AERATION
 Gas concrete :
It is obtained by a chemical reaction of generating
a gas in the fresh mortar , so that when it sets it contains a large
number of gas bubbles .
 Foamed concrete :
It is formed by adding a foaming agent to the mix.

12. PROPERTIES
 Durable .
 Low thermal conductivity .
 Better fire resistance .
 Good resistance to frost .
 Reduced segregation

13. USE
 Heat insulation .
 Fire proofing .
 It is used where concrete is subjected to freezing and thawing
.