Various admixture and functions in concrete

1. Ordinary Concrete
CEMENT
+
FINE AGGREGATE
+
COARSE AGGREGATE
+
WATER

2. USE OF
MINERAL ADMIXTURE IN
CONCRETE
PRESENTED BY:
DILIP SHAH

3. CEMENT
FINE AGGREGATE
COARSE AGGREGATE
WATER
+
ADMIXTURE
(Chemical and
Mineral )
CEMENTITIOUS
MATERIAL
Modern concrete

4. Mineral Admixtures
•Mineral admixtures are finely divided siliceous
materials which are added to concrete in relatively
large amounts, generally in
•the range 20 to 70 percent by mass of the total
cementatious material.
S i l i c a
ti.Jme
S l a g Fly A s h M e t a k a o l l n

5. Fly Ash
•Fly ash is a by-product of the combustion of
pulverized coal in thermal power plants. The
dust collection system removes the fly ash,
as a fine particulate residue, from the
combustion gases before they are
discharged into the atmosphere .

6. Types of mineral admixture
•l.Natural pozzolans: clay and shales, opalinc
cherts,act
•2.Artificial pozzolans: fly ash, blast furnace slag,
silica fume, rice husk ash, surkhi, act...

7. Ecological Advantage
•Power plants using coal as fuel and producing cast iron,
silicon metal, and ferrosilicon alloys are the major
sources of by-products that are being produced at the
rate of millions of tonnes every year in many countries.
•Dumping of these by-products into landfills and streams
amounts to a waste of the material and causes serious
environmental pollution.

8. Effect on Heat of Hydration
Replacement of
cement by fly ash
results in a
reduction in the
temperature rise in
fresh Concrete. This
is particular
importance in mass
concrete where
cooling, following a
large temperature
rise, can lead
to cracking.
50
20 .
! •O -
00 --' "- ,, ,. -20 --2'4--'
Tlmo aflor placing, days

9. Effect of fly ash on properties of
fresh concrete
Concrete using fly ash is
generally reported to show
Reduced segregation and
bleeding and to be more
satisfactory than plain
concrete when placed by
pumping. :
0
o
'
20 40 60 eo 100 120
14o
TlmG, mlnut oa

10. Effect of fly ash on the structural
properties of hardened concrete
At early ages fly ash exhibits
very little cementing value, at
later ages cementing activity
becomes apparent and a
considerable Contribution to
strength may results.
Important variables influence
strength development:
-properties of fly ash
-chemical composition
-particle size
-reactivity
-the temperature and other
curing conditions
AQe -

11. Silica f u me
•Silica fume admixtures are used to meet high
strength and low permeability
requirements.
•They have been used to produce concrete with
compressive Strengths as high as about
142MPa.
•They are added in slurry or in dry form at the
site.

12. Silica fume

13. Benefits are:
• Improves bonding within the concrete,
• Reduced permeability,
• Improves resistance to corrosion,
• Can reduce alkali-silica reactivity (ASR),
• Increased compressive and flexural strengths, and
• Increased durability.

14. 11To know the effect of fly ash on concrete perform
Material used for testing
I.cement
2.aggregate
3.sand
4.fly ash
5.super plasticizer
6.fibre
7.water

15. cement
• All cements which conform to IS can be used for the
prod uction of concrete. 53 grade OPC used for experimental
work.
• Normal consistency = 30%
• Initial setting time = 29 min
• Final setting time = 580min
• Compressive strength
7 days 1.Lll_N/mm2
28 days 49 .55 N/mm 2

16. Aggregate
• Aggregates are the i mportant constituents in concrete. the
give body to the concrete, reduce shrinkage effect economy.
The aggregates occupy 70-80 % of the volume of concrete.
• F.M.= 7.2
• Bulk density(kg /ml)
• (a)Loose:--1 278
• (b)Compacted: 1 530
• Specific gravity:2 .85

17. Sand
• F.M .= 3.04
•passing from 600µ Is sieve according to IS 383-1 970 , Z
•Bulk density(kg /ml) (a)Loose:--1700 (b)Compacted :1 949
•Specific gravity: 2.65

18. Super plasticizer
• I n order to improve the workability, a high range water
reducer super plasticizer added to the mixture. Poly
carboxylate ether(PCE )base, Manufactured by
SIKA,FAI RMATE, ROFF and BASF_tried with basic test.
• Mars cone
• Spread test
• Flow with tumbler

19. Fibre
•Fibre is a small piece of
reinforcing
materi
al
possessing certain
characteristic
properties . They can be
circular, flat or triangular.
The fibre
described
convenient
is often
by a
parameter
called "Aspect Ratio"

20. Water
• Portable water is used for casting of the concrete
mixes.
• It is also used for curing.