S. K. Nath, T. C. Alex, R. Kumar & Sanjay Kumar
CSIR-National Metallurgical Laboratory, Jamshedpur
What is Fly ash
A by-product or the finely divided residue resulting from the
combustion of pulverized coal in thermal power plants.
Potential of Fly Ash
 A alumino-silicate material
 Fine PSD with good flow
ability
 Combination of crystalline
and glassy phases
 Pozzolanic characteristic
 Good durability
 Refractory properties
With right process you can
turn it into a useful product
Waste is a resource,
but in the wrong place
Success stories
Fly Ash
State of the Art
Milwaukee Art Centre, USA
UTAH State
Capitol Building
Bandra Worli Sea Link used
HVFA concrete
BAPS Temple, Chicago
Fly ash Utilization in India
Better than Global Utilization trend
Global Utilization : 39%
Ample scope for new applications and technology
Conventional Fly ash Utilization (%)
Around 72% Fly ash is used in Cement & Building Materials
Fly Ash Research: Global Trend
Fly Ash Utilization in non-conventional way
1. Geopolymer
2. Ceno-sphere separation
3. Extraction of heavy metals
4. Ceramic products
5. High performing Composites
6. Wood & ply-wood substitutes
7. Light weight insulating material
8. Pre-processing
Fly ash R&D at CSIR-NML

First research project on fly ash was carried out in
1968

Main activities started in 1994, focus on high value
added ceramic products

National Seminar on Fly ash in 1999

Preprocessing of fly ash started in 2000, completed
project on cement

Major activities on geopolymer started in 2004, pilot
plant setup in 2011

MoU with C-FARM in 2009

Fly ash is one of the major activities under 12th Five
year plan during 2012-2017
Domain of Fly ash R&D at CSIR-NML
Green Process & Technology
using Geopolymerization of
Fly ash
Geopolymer.........
Synthetic alkali aluminosilicate material
Geopolymer can be described by
the general formula
Mn [ – (SiO2)z – AlO2 ]n . wH2O
M
z
n
: Alkaline element,
: 1, 2 or 3, and
: Degree of polymerization
Why Geopolymer …
Simple process
Wide range of
applications
80% less CO2 generation
than OPC
Low energy & water
consumption
Better durability &
longevity
Qualifies as GREEN
Excited Examples: Geopolymer Concrete
Geopolymer concrete
sleepers of operating railway, StPetersburg – Moscow were placed in 1988
and operational.
Geopolymer Concrete
Geopolymer in Airport runway
>20 MPa strength
in 4 hours
Why Fly Ash is Suitable ??
<100 µm
particle size
Flow
behaviour
Si-Al ratio 1.6
– 2.2
Synthetic
material
>30% glassy
phase
Suitability in Indian Context
 Abundantly available
 Either free of cost or low cost material
 Cement making is of great concern due to
depleting natural resources and increasing CO2
generation
 100% utilization of fly ash notification by MoEF,
Nov. 2009
 Exploit the full potential of fly ash as source of
silica and alumina: >90% fly ash can be used in
many products
 Indian fly ash is suitable for geopolymerization
 The average ambient temperature in India is
27°C and average humidity is >50%,
CSIR-NML Research on
Fly Ash Geopolymer
Self glazed tiles
 Low temperature processing
 No additional process for glazing
Properties
Values
Dimension tolerance
Straightness of sides
Surface flatness
 0.5%
 0.5%
 0.5%
Water absorption, %
Moh’s hardness
Compressive strength
14-16
5
>150 kg/cm2
Patent : 2626/DEL/2005, 30/09/2005 and 728/DEL/2006, 30/11/2005
Paving blocks
Synergistic Utilization of fly ash, BF slag, COREX slag, steel
slag, zinc slag and kiln dust
 Ambient temperature processing
 Ready to use in 7 days
 Product confirms IS-15658:2006
specification
Properties
Pavement tiles
Compressive strength
(MPa)
Flexural strength (MPa)
Bulk density, gm/cc
Water absorption, %
Abrasion resistance, mm
20-40
5-7
2.8
6-7
0.7
Lab Scale to Pilot
Scale
Geopolymer pilot plant – 1st in India
Supported by FAU- Department of Science & Technology
A step forward in translating process into technology

Fully automatic, with ~4
ton/shift capacity

Can produce different
shapes paving blocks

Uses
vibration,
or
hydraulic
pressing or
combination of both
Pre-processing of fly
ash
Methods
Processing
Principle
methods
Air classification Size classification
based on shape, size
and density of fly ash
Applications
Triboelectric
separation
Charge separation
 Separation of carbon
Mechanical
activation
Increase in surface
area, creation of bulk
& surface defects
 Increased utilization in
blended cement
 High strength geopolymers
 Separation of different size
fraction of fly ash
 Separation of cenosphere
Air Classification using ATP50
High speed air classifier
with max rotation speed
20000, can classify very
fine fractions also
Use of different size fraction in PPC
Strength Development !!
Coarse fraction shows lot of
un-reacted fly ash particles
even after 28 day hydration
More reaction product in the
fine fraction is the reason for
strength development
Mechanically Activated
Fly Ash
What is Mechanical Activation
Changes that takes place during
mechanical activation
 Increase in surface area
 Stresses in solid structure
 Defects induced in the solid
structures
 Phase transformations
 Repeated welding of interfaces
 Fracture leading to dynamic
creation of fresh surfaces for
reactions
 Chemical reactions
Strength Development in cement
MA Fly ash in Geopolymer
X50 ~ 5 μm
60 oC
X50 ~ 5 μm
X50 ~ 3 μm
X50 ~ 36 μm
Geopolymer Cement
Very high
(120 MPa)
strength
Ceramics using Fly
Ash
Wear Resistant Ceramics
 Excellent
compressive strength
 Very hard and dense
 Excellent wear
resistant properties
 Can be used for wear resistant
applications in pipelines, chutes,
bunkers, hoppers, mills etc
Fly ash (30-40 wt% ) based wear resistance ceramics
substitute for high alumina based ceramic tiles
Refractory Bricks
 50% fly ash can be used
 Equivalent of IS-6 fire-clay bricks
 Sintered at lower temperature
Properties
Refractory
brick
IS-6
% AP
24.5
25.0 (max)
BD (g/cc)
1.9
2.0 (min)
CCS (Kg/cm2)
300
250 (min)
Al2O3 %
Fe2O3 %
30.7
3.5
30.0 (min)
2.0 (max)
Ceramic Tiles
 Produced at 980-1050 C
 Improved scratch hardness
 Better compressive
strength
 Satisfy EN specification
 Possibility to use other
waste in addition to fly ash
Patent No. DEL/1800/96, 005NF and 13005NF 1998/03
Thank You
We are caring for environment
Fly ash Utilization: A Giant Leap
Year 2009
Generation
Utilization
Source: ACAA
: 6.5 billion tonnes
: 39%
Geopolymer as Products
 Blended cements for structural
applications
 Enhanced acid and fire resistant cements
 Toxic waste encapsulation
 Advanced composites (high temperature
ceramic)
 Adhesives
Commercial Realty
Zeobond, Australia is
making geopolymer
concrete, using fly ash as
one of the component
Geopolymer Pilot Plant: 1st in India






Provide valuable design and operational data for
the setting up of a large size plant,
Assess the impact of variability of raw materials
(fly ash, water etc) quality,
Fine tune operational parameters,
Work out a more precise techno-economics for
the process,
Act as demonstration unit and instill confidence in
potential user of the technology since the
technology would be used in India for the first
time,
Development of other geopolymer products since
the plant has a modular character
Immense Application Potential
Area
Applications
Civil engineering
Low CO2 Fast setting cement, Precast concrete products
Ready mixed concrete
Building materials
Bricks, blocks, pavers, self glazed tiles, acoustic panels,
pipes,
Archeology
Repairing & restoration
Composite material
Functional composite for structural ceramic application
Fire resistant material
Fire and heat resistant fiber composite material
Refractory application
Refractory moulds for metal casting, Refractory castables
Immobilization of toxic
encapsulation of domestic, hazardous, radioactive and
materials
contaminated materials in a very impervious, high
strength material
Others
Paints, Coatings, Adhesive
Geopolymer
Simple processing
Low energy consumption
Low CO2 generation
Low water requirement
Low cost
Fly ash Easily available
Good properties
Reactivity of MA Fly ash
o
Temperature : 27 C
w/c ratio : 0.5
14
12
VMFA25%
AMFA25%
VMFA50%
AMFA50%
IC-B (~ 20% FA)
mW
10
8
6
4
2
0
0
10
20
30
40
50
Time, h
60
70
80
90 100
What is Mechanical Activation
Changes that takes place
Degree of dispersion
Grinding and Mechanical Activation
Rittinger
Stage
Aggregation
Agglomeration
Grinding time, h
z = efficiency of grinding
Wz = work expended during grinding
E = change in bonding energy due to grinding
e = specific surface energy
as = specific surface area
 Increase in surface area
 Stresses in solid structure
 Defects induced in the solid
structures
 Phase transformations
 Localised and overall
thermal effects
 Repeated welding of
interfaces, and
 Fracture
leading
to
dynamic creation of fresh
surfaces for reactions etc.
 Chemical reactions
Mechanical Activation Devices
TVA Coal Ash Pond Rupture- 2008
Paving Blocks from Industrial Waste
Paving Blocks
Total CO2 generation / ton
Water requirement/ ton
Waste & by-products
reuse/ ton
Embodied energy/ kg

Combination of fly ash, steel slag
and granulated blast furnace slag
has been used,

Meet
all
the
obligatory
specification as per IS 15658:
2006,

Complied with the USEPA limit
for leaching of toxic metals and is
environmentally safe,
Cement based
Steel slag based
180 -200 kg
(from firing of cement)
300 liters
16 - 20kg (conversion of
alkali carbonate into oxide)
250 liters
<75 kg
>900 kg
1.2 MJ
0.8 MJ
What are Supplementary Cementing Materials?
Pozzolan – a siliceous or alumino-siliceous material that, in finely
divided form and in the presence of moisture, chemically reacts at
ordinary temperatures with calcium hydroxide (released by the
hydration of Portland cement ) to form compounds possessing
cementing properties
A hydraulic cement reacts chemically with water to form
compounds (hydrates) that have cementing properties – e.g.
Portland cement
Why Geopolymer …
Cement type
Manufacturing
temperature
Energy
consumption
CO2 emission
Portland
1450-1500°C
100
100
Glass
750°C-1350°C
64 (-36%)
35 (-65%)
Carbunculus™
nat. 20-80°C
30 (-70%)
20 (-80%)
Source: www.geopolymer.org
Synthetic Granite Tiles
Potential
substitute for
natural granite
 Very dense
 Macro defects free body
 Excellent mechanical
properties
Pat. No. DEL/1800/96