Flyash

 Puzzolona puzzouli, a town in italy near mount
Vesuvious.
 Volcanic dust around this town when mixed with
hydraulic lime was found to possess hydraulic or
cementitious properties.
 Puzzolona may be defines as a siliceous material which
whilst itself doesn’t possess cementitious properties.
 Before cement, these puzzolonas were mixed with
lime.
 Puzzolonas may be natural or artificial, flyash being
common in latter category.
 Currently, its use to replace some portion of cement in
concrete.

 ECONOMY
 WORKABILITY INCREASED
 REUCTION OF BLEEDING AND SEGREGATION
 GREATER IMPERVIOUSNESS
 RESISTANCE TO FREEZING AND THAWING
 RESISTANCE TO ATTACK SULPHATES & WATERS.
 REDUCED EFFECTS OF ALKALI AGGREGATE
REACTION
 REDUCED HEAT OF HYDRATION
 REDUCED COSTS
 LOCALLY OBTAINED

 NATURAL
 CLAY
 SHALES
 DIATOMACEOUS EARTH
 VOLCANIC TUFF & PUMICITES
 RHENISH AND BAVARIAN TRASS
 ARTIFICIAL
 FLYASH
 GROUND BLAST FURNACE SLAG
 SILICA FUME
 SURKHI
 RICE HUSK ASH

 When mixed with OPC, the silica of puzzolona
combines with free lime released during the hydration
of cement, called puzzolonic action.
 The silica contributes to development of strength.
 Slowly additional calcium silicate hydrate is formed
which is a binder and fills up the space, gives
impermeability, durability and increase in strength.
 Silica of amorphous form reacts with lime readily than
those of crystalline form.

 The optimum amount of puzzolona, as replacement
for cement may normally range between 10-30 %.
 Enough moisture has to be made available for a long
time to complete puzzolonic action.
 Chief application where heat of hydration is to be
reduced and slower rate of gain in strength is not an
issue, mass concreting like dams, massive foundations,
retaining walls etc.,

 Pulverised fuel ash (PFA)
 Comprises of fine particles which rise with theflue
gases.
 Reisdue from combustion of pulverised coal
collected by electro static separators from power
plants.
 Finer than OPC.
 Consists of spherical particles or irregular shaped
particles.
 Light grey to dark grey or even brown.
 Also used as admixture.
 Carbon content should be as low as possible.

 It is a heterogeneous material containing SiO2, Al2O3 and
Fe2O3 as major constituents with CaO occasionally being
the minor constituent.
 Exact composition varies according to the parent coal
bed makeup.
 Also has Arsenic, Beryllium, Cadmium, Chromium,
Cobalt, Mercury, Molybdenum, Selenium, Strontium, etc
(in the order of hundred ppm).
Component(%) Bituminous Sub-Bituminous Lignite
SiO2 20-60 40-60 15-45
Al2O3 5-35 20-30 20-25
Fe2O3 10-40 4-10 4-15
CaO 1-12 5-30 15-40
CHEMICAL COMPOSITION

 Fineness should be as high as possible because the
silica in flyash combines slowly over a very long
period with lime liberated during hydration
process.
 Curing at a temperature of 38 degrees C has been
found to greatly accelerate its contribution to the
strength of concrete.
 Flyash is supplied in two grades:- grade I & grade
II.
 Grade I is recommended for manufacturing of
OPC.
 Grade II is used in cement mortar & as admixture
in concrete.

 Spherical glassy materials ranging from 1 to 150
micron, most of which passes through a 45 micron
sieve.
 More than 40 % of the particles which are under 10
microns contribute to early age strength.
 Particles of sizes 10 to 45 microns reacts slowly and are
responsible for gain in strength from 28 days to one
year.

 Admixture for Portland Cement
 Soil Stabilization
 Flyash Bricks
 Asphalt Concrete
 Embankments
 Geopolymers
 As a catalyst
 Waste Treatment

 Fly ash, being primarily pozzolanic, can actually
replace a percentage of the Portland cement, to
produce an even stronger, more durable and
more environment friendly concrete.
 The initial compressive strength is low but as
days pass, flyash concrete gains more strength
and eventually has a lot more strength as
compared to normal Portland cement.
 Significantly reduces the release of CO2 into
theatmosphere.
 Can be used for construction of structures
on/under water.
PORTLAND CEMENT

 On Amount Of Water:-Requires little more amount of
water as the fineness of flyash is more for fine sands.
For coarse sand the addition of flyash produces
beneficial results.
 Strength:- lower rate in gaining strength as compared
to OPC but increases after 3 months provided curing is
continued.
 Shrinkage:- finer flyash & low carbon content reduces
shrinkage.
 Permeability : reduces
 Resistance to chemical attack:- increases.
 Heat of hydration :- reduces
 Setting time:- increase in setting time upto 2 hrs.

10
0
20
30
60
50
40
3 7 28 56 90 180
Plain
Cement
Concrete
Flyash
Concrete

 Soil stabilization is the alteration of soil properties
to improve the engineering performance of soils.
 Modification of soil properties is the
temporary enhancement of sub-grade
stability to speedup construction.
 Stabilization can increase the shear strength of a
soil and/or control the shrink-swell properties of a
soil, thus improving the load-bearing capacity of a
sub- grade to support pavements andfoundations.
 Stabilization can be used to treat a wide range of
sub- grade materials from expansive clays to
granular materials.
SOIL STABILIZATION & MODIFICATION

• Fly ash possesses both ceramic
as well as pozzolanic
properties and therefore can be
utilized in a unique way for
manufacturing bricks.
• This proves to be very useful
for building construction.
• These bricks produced by the
new process are superior in
quality as they offer higher
cold crushing strength and
smooth, uniform size.
FLYASH BRICKS

S.NO FEATURES NORMALCLAY
BRICKS
FLYASHBRICKS
1 BINDING LIGHT DENSE
2 COLOUR VARY UNIFORM
3 SHAPE IRREGULAR UNIFORM
4 WEIGHT MORE LESS
5 COMPRESSIVE
STRENGTH
35KGS/SQ.CM 100KGS/SQ.CM
6 WATER
ABSORPTION
20-25% 6-12%

a) In terms of usability in Concrete and Cement:
 Higher Ultimate Strength
 Increased Durability
 Improved Workability
 Reduced Bleeding
 Increased Resistance to SulfateAttack
 Reduced Shrinkage
 Almost zero emission of greenhouse gases.
ADVANTAGES

 Reduces excavation of clay.
 Low cost of brick as compared to clay brick of
same quality.
 Number of bricks required per unit volume of
construction is less as dimensional accuracy is
maintained.
 Lesser consumption of mortar.
 Better resistance to water damage.

 Reduces soil erosion by replacing top soil
asingredients for most construction mixes.
 Reduces pollution measure by re-use of wastes.
 Reduces the amount of greenhouse gases being added
to the atmosphere.
 Hydrophobic nature helps in proper draining off
ofwater from roads and structures.
 Production of crude oil frompolyethylene.
 Also used in sewage treatment and generation
ofbiofuel as an alternate source of energy
resource.

 Groundwater contamination due torunoffs
carrying ill-treated flyash.
 Cannot be used for structures requiring shorter
setting time, a demand which is expected by most of
the engineers and builders.
 Air content control plays a vital role and can
prove crucial for the quality of flyash concrete.
Toomuch reduction in air content can be
disastrous.
 It is very difficult to use in winter season due to further
increase in already longer setting time.
 Difficult to control colour of cement containing
flyash. Hence, a bit problematic to use where
cosmetic quality plays a significant role.
DISADVANTAGES

 Flyash can be proclaimed as one of the
mostadvantageous waste material.
 Using it as a construction material will not only help
inits disposal but will also add strength and durablity
of structures.
 Since, the current usage of flyash in India is still
around 25%and below 45% even in the developed
countries like United States, there is a huge scope
for flyash in upcoming years.
 So let us harness a billion dollar resource that has
beenwasted so far.
CONCLUSION

Flyash

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Flyash