basic knowledge about performance and characteristics of fly ash based concrete. this was my first presentation....so hard core civil engineers might consider me a layman!... anyway its a good way to start knowing gist and basics.

1. A QUALITATIVE APPROACH
MANISH KUMAR MANDAL
DEPARTMENT OF CIVIL ENGINEERING
2ND YEAR
VEL TECH HIGH TECH ENGINEERING COLLEGE
by

2. FLY ASH-INTRODUCTION
 Fly ash is a fine powder produced as a product from industrial plants using
pulverized coal or lignite as fuel.
 It is the most widely used pozzolan siliceous or aluminosiliceous in nature
in a finely divided form.
 They are spherical shaped “balls’’ finer than cement particles.

3. FLY ASH AS A SUPPLEMENTARY:
Apart from technical advantages it attributes to the concrete properties, fly ash
has its own benefits
 Problem of disposal:
In India alone, we produce 75 million tons of fly
ash every year, the disposal of which has become a
serious environmental problem. The effective use
of fly ash in concrete making is therefore attracting
serious considerations of concrete technologists
and government departments.

4. Global CO2 emissions:
 Global cement production is about 1.3 billion
tons in 1996 and production of every 1 ton of cement
emits 0.87 ton of carbon dioxide.
 In broader terms, 7% of global CO2 emissions can
be attributed to Portland cement industry.

5. FLY ASH IN CONCRETE:
 Fly ash could be an expensive replacement for Portland cement in concrete and
using it, improves strength, segregation and ease of pumping concrete.
Fly Ash particles provide a greater
workability of the powder portion of the
concrete mixture which results in greater
workability of the concrete and a lowering of
water requirement for the same concrete
consistency.
The rate of substitution typically specified is
a minimum of 1 to 1 ½ pounds of fly ash to 1
pound of cement

6. CHEMICAL COMPOSITION
MATERIALS PORTLAND
CEMENT%
FLY ASH%
SiO2 21.82 53.39
Al2O3 6.49 16.07
Fe2O3 1.93 13.05
CaO 60.74 6.33
MgO 1.08 5.48
SO3 2.62 1.06
Na2O 0.14 1.59
Free Cao 0.84 0.11
1. fly ash are amorphous
(glassy) due to rapid cooling;
those of cement are
crystalline, formed by slower
cooling.
2. Portland cement is rich in
lime (CaO) while fly ash is
low. Fly ash is high in
reactive silicates while
Portland cement has smaller
amounts

7. COMPARISON BETWEEN CLASSES OF FLY ASH

8.  Class F is fly ash produced from burning anthracite or
bituminous coal, and Class C is produced from the
burning of sub-bituminous coal and lignite.
 Class F is low in lime, under 15 percent, and contains a
greater combination of silica, alumina and iron (greater
than 70 percent) than Class C fly ash.
 Class C fly ash comes from coals which may produce an
ash with higher lime content — generally more than 15
percent often as high as 30 percent. Elevated CaO may
give Class C unique self-hardening characteristics.

9. The fly ash from boilers where
mechanical collectors
are used is coarser than fly ash
from electrostatic precipitators.
 The color varies from light to
dark grey depending upon its
carbon contents.
 The quality of fly ash varies
from source to source.
 fly ash particles are small, they
effectively fill voids
PHYSICALASPECTS:

10. Though fly ash offers environmental
advantages it also improves the:
 performance and quality of concrete.
 Fly ash affects the plastic properties of concrete
by improving workability
 Reduces water demand
 Reduces segregation and bleeding.
Lowers heat of hydration.
 Fly ash increases strength
Reduces permeability

11. MECHANICALATTRIBUTES:
The main benefit of fly ash in concrete is that it not only
reduces the amount of non durable calcium hydroxide
(lime), but in the process converts it into calcium silicate
hydrate (CSH), which is the strongest and most durable
portion of the paste in concrete.
REACTION WITH MOISTURE:

12. HEAT OF HYDRATION:
•Fly Ash has a lower heat of hydration.
•Portland Cement produces considerable heat upon hydration.
•In mass concrete placements the excess internal heat may contribute to
cracking.
•The use of Fly Ash may greatly reduce this heat build up and reduce
external cracking.

13. COMPRESSIVE STRENGTH:
 Typically, concrete made with fly ash will be slightly lower in
strength than straight cement concrete up to 28 days, equal
strength at 28 days, and substantially higher strength within a
year’s time.
 Thus, fly ash concrete achieves significantly higher ultimate
strength than can be achieved with conventional concrete.

14. COMPRESSIVE STRENGTH TEST:

15. FLY ASH CONCRETE:
NEED FOR EXTENDING STRENGTH
SPECIFICATIONS BEYOND 28 DAYS
 Developing sustainable concrete to last more than 100
years requires extending the 28-day specifications.
 Extended age parameters can assure more durable
concrete.
 Proper mix designs can be developed to optimize the
projects timeline.

16. PROJECTS AND THEIR AGE ACCEPTANCE:
project Fly ash% Age strength acceptance
Naval facilities
engineering
25-40% 28-56 day acceptance
Olivenhain dam
San Diego
65% 365 day acceptance
Washbum airport 35% 28-,56-and 90-day
acceptance
Caltrans 25-35% 42 days

17. CONCLUSION:
Fly ash thus holds a vast potential for improving the modern
day concrete when it comes to quality in the long term. In
spite of being an industrial waste, it can improve
durability and reduce heat of hydration.
The prospects of fly ash are still being underused even
today. Thus keeping in mind about environmental
concerns and its indispensability as a mineral admixture,
the values of fly ash should be effectively garnered .

18. REFERENCES:
 Concrete technology(theory and practice) –M.S shetty
 Activation of fly ash through
Nanomodification- ACI spring convention Shiho Kawashima,
Columbia University
 Enhancing performance of high volume fly ash concrete –ACI
spring convention.
 http://www.concretebasics.org/articlesinfo/fa8.php#sthash.r8p7
Ivtk.dpuf
 magazine of concrete research- volume 64

19. THANK YOU