2. DEFINITION
concrete which uses lightweight aggregates
May consist of lightweight aggregates are
used in ordinary concrete of coarse aggregate
and sand, clay, foamed slag, clinker, crushed
stone, aggregates of organic and inorganic.
3. Methods of preparation of
lightweight concrete
2.Without providing
concrete smoother
1.Preparation of porous (rough concrete)
concrete
3.Providing lightweight
aggregate concrete
4. 1.PREPARATION OF POROUS
CONCRETE
a) Lightweight concrete obtained by
inserting gas bubbles or air into the mixture
of plastic cement (mixed with fine sand)
b) Lightweight concrete did not contain
stones included as porous mortar.
5. Characteristics of porous concrete :
1. high
thermal
insulation
2. a high
moisture
movement
3. a high
shrinkage
POROUS CONCRETE
6. Types of porous concrete
a) type of
cast in situ
b) type of
first cast
7. Aggregates used shall comply with
the following conditions:
a) At least c) Stone did
95% of not diffuse
aggregates through the
must be via b) The stone BS 4mm
the 18mm aggregate used sieve.
BS sieve. shall not
exceed 10% by
10 mm BS
sieve.
8. 2. Preparation of concrete without
the smooth (rough concrete)
Lightweight concrete such as is
obtained when the fine aggregate
(sand) is not used and the
concrete mix of cement, water and
coarse aggregates.
Concrete can be used for
structural purposes and not to
bear burden to bear a load.
9. 3. Preparation of lightweight
aggregate concrete
• Concrete is often used in:
b) the roof and
walls cast in
situ for use in
insulation.
a) before
pouring the
concrete block
feature of lightweight aggregate concrete.
10. The main purpose of the concrete
requirements are:
c) have low
b) have a low
a) has sufficient drying shrinkage
density (for
strength (to avoid
better insulation)
cracking/rift)
11. The above factors depend on:
a) types of
aggregates
used b) the
mixture
c) the d) the
density methods and
techniques of
preservation
13. Thermal insulation
Thermal insulation efficiency is defined as resistance
to heat flow either through conduction, or radiation.
Lightweight concrete has a high heat insulation
resistance.
such as porous concrete walls 150mm to provide four
times better insulation than 225mm thick brick wall.
14. Fire insulation
• Fire prevention is associated with thermal
insulation.
two types
of fire
protection
b) a non-combustible
a) combustible materials - such as
materials - such non-organic materials
as organic such as
wood stone, bricks, rocks
and other.
15. Durability
It is defined as the ability to bear the effects of environment
such as the effects of chemical, physical stress and mechanical
effects. The intended effect of the chemical, including ground
water containing sulfate, air pollution and reactive liquid spills.
Physical stress is the shrinkage, the stresses of
temperature, cooled, and others. If all the physical stress will
cause cracks in the structure of lightweight concrete.
Mechanical effect is the impact and costs are excessive. The
situation in the steel structure unit should be protected from
rusting.
16. Water absorption
Absorption water by the concrete is high and
more than that found in solid concrete. This is
because the lightweight concrete has holes in it.
18. Acoustic properties
The key factor is the density of
the sound insulation material.
Therefore, for sound
insulation, lightweight concrete
can not show the desired
characteristics.
19. ii) Economical in
i) rapid and terms of
relatively transportation as
simple well as reduction
construction in manpower
Advantages
iv) Most of lightweight
concrete have
iii) Significant reduction better nailing and sawing
of overall properties
weight results in saving than heavier and stronger
structural convensional concrete
frames, footing or piles
20. Disadvantages i) Very sensitive with
water content
in the mixtures
iii) Mixing time is
longer than
ii) Difficult to place and finish conventional
because of the porosity and concrete to assure
angularity of the aggregate. In proper mixing
some mixes the cement mortar
may
separate the aggregate and float
towards the surface