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.

A alumino-silicate material Fine PSD with good flow

ability Combination of crystalline

and glassy phases Pozzolanic characteristic Good durability Refractory properties

Potential of Fly Ash

Waste is a resource, but in the wrong place

With right process you can turn it into a useful product

Waste to Resource

The Changing Mindset

Fly AshS

ucc

ess

sto

ries

State of the ArtMilwaukee Art Centre, USA

BAPS Temple, ChicagoUTAH State Capitol Building

Bandra Worli Sea Link used HVFA concrete

Fly ash Utilization in India

Ample scope for new applications and technology

Better than Global Utilization trendGlobal Utilization : 39%

Conventional Fly ash Utilization (%)

Around 72% Fly ash is used in Cement & Building Materials

Fly Ash Research: Global Trend

1. Geopolymer2. Ceno-sphere separation3. Extraction of heavy metals4. Ceramic products5. High performing Composites6. Wood & ply-wood substitutes 7. Light weight insulating material8. Pre-processing

Fly Ash Utilization in non-conventional way

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 & Green Process & Technology using Technology using Geopolymerization of Geopolymerization of Fly ashFly ash

Geopolymer.........

Simple process

Wide range of applications

80% less CO2 generation than OPC

Low energy & water consumption

Better durability & longevity

Qualifies as GREEN

Why Geopolymer …

Geopolymer concrete sleepers of operating railway, St-Petersburg – Moscow were placed in 1988 and operational.

Excited Examples: Geopolymer ConcreteExcited Examples: Geopolymer Concrete

>20 MPa strength in 4 hours

Geopolymer in Airport runway

Geopolymer Concrete

Si-Al ratio 1.6 – 2.2

>30% glassy phase

<100 µm particle size Flow

behaviour

Synthetic material

Why Fly Ash is Suitable ??

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%,

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%,

Suitability in Indian Context

CSIR-NML Research on Fly Ash

Geopolymer

Patent : 2626/DEL/2005, 30/09/2005 and 728/DEL/2006, 30/11/2005

Self glazed tiles

Properties Values

Dimension toleranceStraightness of sidesSurface flatness

Water absorption, %Moh’s hardness Compressive strength

0.5% 0.5% 0.5%

14-165>150 kg/cm2

Low temperature processing

No additional process for glazing

Synergistic Utilization of fly ash, BF slag, COREX slag, steel slag, zinc slag and kiln dust

Paving blocks

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

Ambient temperature processing

Ready to use in 7 days

Product confirms IS-15658:2006 specification

Lab Scale to Pilot Scale

Fully automatic, with ~4 ton/shift capacity

Can produce different shapes paving blocks

Uses vibration, or hydraulic pressing or combination of both

Supported by FAU- Department of Science & Supported by FAU- Department of Science & TechnologyTechnology

A step forward in translating process into technologyA step forward in translating process into technology

Geopolymer pilot plant – 1st in India

Pre-processing of fly ash

Pre-processing of fly ash

Processing methods

Principle Applications

Air classification Size classification based on shape, size and density of fly ash

Separation of different size fraction of fly ash

Separation of cenosphere

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

Methods

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

X50 ~ 5 μm

X50 ~ 5 μm

X50 ~ 3 μm

X50 ~ 36 μm

60 oC

MA Fly ash in Geopolymer

Very high (120 MPa) strength

Geopolymer Cement

Ceramics using Fly Ash

Wear Resistant Ceramics

Fly ash (30-40 wt% ) based wear resistance ceramicssubstitute for high alumina based ceramic tiles

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

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 : 6.5 billion tonnesUtilization : 39%

Source: ACAA

Geopolymer as Products

Blended cements for structural applications

Enhanced acid and fire resistant cements

Toxic waste encapsulation

Advanced composites (high temperature ceramic)

Adhesives

Zeobond, Australia is

making geopolymer

concrete, using fly ash as

one of the component

Zeobond, Australia is

making geopolymer

concrete, using fly ash as

one of the component

Commercial Realty

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

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

Geopolymer Pilot Plant: 1st in India

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

materials

encapsulation of domestic, hazardous, radioactive and

contaminated materials in a very impervious, high

strength material

Others Paints, Coatings, Adhesive

Immense Application Potential

Low costEasily availableGood properties

Geopolymer

Simple processingLow energy consumptionLow CO2 generationLow water requirement

Fly ash

Towards Sustainability

Fly Ash,

Geopolymer

& Sustainability

Reactivity of MA Fly ash

0 10 20 30 40 50 60 70 80 90 1000

2

4

6

8

10

12

14 Temperature : 27 oCw/c ratio : 0.5

m

W

Time, h

VMFA25% AMFA25% VMFA50% AMFA50% IC-B (~ 20% FA)

Grinding and Mechanical Activation

Grinding time, h

Deg

ree

of d

ispe

rsio

n

E

=

E u -

(e a s

) =

sW

z z

Wz =

E

= e

as

sW

z =

E

=

(e a s

)

AgglomerationAggregationRittinger

Stage

z = efficiency of grindingWz = work expended during grindingE = change in bonding energy due to grindinge = specific surface energyas = specific surface area

What is Mechanical Activation

Changes that takes place

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 WastePaving Blocks from Industrial Waste

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,

Paving Blocks Cement based Steel slag based

Total CO2 generation / ton 180 -200 kg(from firing of cement)

16 - 20kg (conversion of alkali carbonate into oxide)

Water requirement/ ton 300 liters 250 liters

Waste & by-products reuse/ ton

<75 kg >900 kg

Embodied energy/ kg 1.2 MJ 0.8 MJ

What are Supplementary Cementing Materials? Pozzolan – a siliceous or alumino-siliceous material that, in finelydivided form and in the presence of moisture, chemically reacts atordinary temperatures with calcium hydroxide (released by thehydration of Portland cement ) to form compounds possessingcementing properties

A hydraulic cement reacts chemically with water to formcompounds (hydrates) that have cementing properties – e.g.Portland cement

Cement typeManufacturing 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

Why Geopolymer …Why Geopolymer …

Synthetic Granite Tiles

Pat. No. DEL/1800/96

Potential substitute for

natural granite Very dense

Macro defects free body

Excellent mechanical properties