The presentation made by Dr J D Bapat illustrates the importance of fly ash utilisation. The slides depict how fly ash is used in cement and concrete to improve its strength and durability.

1. CEMENT & CONCRETE:
PROMISE OF FLY ASH
FLY ASH UTILISATION INTERACTIVE WORKSHOP
11 JULY 2014, MUMBAI
MISSION ENERGY FOUNDATION, MUMBAI

2. FLY ASH
RELEVANCE FOR INDIA
IN INDIA 60% POWER FROM COAL
COAL HAS LOW CALORIFIC VALUE
& VERY HIGH ASH CONTENT
ASH GENERATION: 175 MILLION
t/a & CEMENT PRODUCTION
CAPACITY: 350 MILLION t/a

3. FLY ASH
ENERGY & GHG SAVER
CEMENT TYPE THERMAL ENERGY ELECTRICAL ENERGY
PC 100 100
PPC (15%) 84 89
PSC (50%) 47 79
• CEMENT INDUSTRY CONTRIBUTES 5%
OF TOTAL ANTHROPOGENIC CO2
EMISSIONS GLOBALLY

4. FLY ASH
ASTM CLASSIFICATION
• ASTM C618 CLASSIFICATION:
ASTM CLASS FAS DESCRIPTION
N (>70%) RAW OR CALCINED NATURAL POZZOLAN,
EXAMPLE: METAKAOLIN
F (>70%) FA WITH POZZOLANIC PROPERTIES,
PRODUCED FROM ANTHRACITE OR
BITUMINOUS COAL
C (>50%) FA WITH POZZOLANIC AND CEMENTITIOUS
PROPERTIES, PRODUCED FROM LIGNITE
SUBBITUMINOUS COAL,
LIME CONTENT > 10%
• FAS: Fe2O3 + Al2O3 + SiO2
• RETENTION ON 45 MICRON (325 MESH) SIEVE (%, MAX): 34%

5. FLY ASH
ASTM CLASSIFICATION

6. FLY ASH
INDIAN STANDARD
IS 3812 REQUIREMENT
• GRADE I, BITUMINOUS, SIMILAR
TO ASTM TYPE F:
Fe2O3 + Al2O3 + SiO2 = MIN 70%
• GRADE II, LIGNITE, SIMILAR TO
ASTM TYPE C:
Fe2O3 + Al2O3 + SiO2 = MIN 50%

7. FLY ASH IN CONCRETE
INDIAN STANDARD
IS 456 REQUIREMENT FOR REINFORCED CONCRETE
(i) MINERAL ADMIXTURES FA, GGBS, SF, RHA, MK
(ii) ADDITION LIMITS (%) FA: 15-35, GGBS: 25-70
(iii) CONCRETE M 20-M 80
(iv) CEMENT CONTENT (kg/cu.m)
EXCLUDING ADMIXTURE (MAX) 450
v) w/b RATIO(MAX) 0.4-0.55
(vi) CHLORIDE (MAX, kg/cu.m) 0.4-0.6
(vii) SULPHATE SO3 (% CEMENT m) 4

8. FLY ASH
PARTICLE SHAPE
SPHERICAL CENOSPHERES

9. FLY ASH
PARTICLE SHAPE
PLEROSPHERES: CRACKED SPHERES

10. FLY ASH IN CONCRETE:
EFFECT OF PARTICLE SHAPE
• SHAPE FA PARTICLES AFFECT
WATER REQUIREMENT OF
CONCRETE
• SPHERICAL PARTICLES CREATE
BALL BEARING EFFECT
• THAT IMPROVES ITS FLOW
PROPERTIES & REDUCE WATER
REQUIREMENT

11. FLY ASH IN CONCRETE:
EFFECT OF PARTICLE SIZE
• POZZOLANIC REACTIVITY OF FA WAS MORE
AFFECTED BY FINENESS THAN GLASS CONTENT
• PARTICLES IN RAW FA RANGE MOSTLY FROM 1
TO 100 MICRON
• PARTICLES UNDER 10 MICRON: EARLY (7 & 28
DAY) STRENGTH,
10-45 MICRON: LATE STRENGTH UP TO 1 YEAR
ABOVE 45 MICRON: INERT & ACT AS FILLER

12. FLY ASH IN CONCRETE:
EFFECT OF UNBURNED CARBON
MINIMISE UNBURNED CARBON
• CARBON PARTICLES DO NOT TAKE PART IN CHEMICAL
REACTIONS DURING CEMENT HYDRATION BUT INFLUENCE
ITS WATER DEMAND FOR STANDARD CONSISTENCY
• INCREASE REQUIREMENT OF AIR-ENTRAINING AGENTS
(AEA)
• FOAM INDEX (FI) IS IMPORTANT QUALITY CONTROL TEST
TO DETERMINE EFFECT OF UBC IN FA
• FA WITH < 3%–4% CARBON DOES NOT SERIOUSLY AFFECT
PERFORMANCE OF ORGANIC CHEMICAL ADMIXTURES

13. FLY ASH IN CONCRETE:
FLUIDISED BED FA
 ASH PARTICLES FROM FB ARE LARGER &
LESS SPHERICAL IN COMPARISON TO FA
PRODUCED IN CONVENTIONAL PULVERIZED
COAL FIRED SYSTEMS
 IRREGULARITY OF SHAPE MAY NOT GIVE
DESIRED RESULTS IN TERMS OF LOWERING
WATER-TO-CEMENT RATIO
 FLUIDISED BED FA IS MOSTLY NON-
STANDARD

14. FLY ASH IN CONCRETE:
PETCOKE CO-COMBUSTION FA
 CO-FIRING OF COAL WITH PETCOKE ADDS MORE UBC
& COARSENESS TO FA
 ASH CONTENT JUST 0.5%
 INCREASE IN CARBON CONTENT EXPECTED TO
REDUCE EFFECTIVENESS OF AEA
 HIGH VANADIUM CONTENT: GETS INCLUDED INTO
SOLID CONCRETE STRUCTURE
 USE OF PETCOKE PFA HAS NO DETRIMENTAL
EFFECTS ON CONCRETE STRENGTH DEVELOPMENT

15. FLY ASH IN CONCRETE:
QUALITY IMPROVEMENT
 REMOVAL OF UBC PARTICLES, OBTAINING
PROPER PARTICLE SIZE (< 10 MICRON) & SIZE
DISTRIBUTION ARE PRINCIPAL TASKS OF FA
PROCESSING
 INCREASED STRENGTH, GREATER POZZOLANIC
REACTIVITY & LOWER WATER DEMAND
 IMPROVED CONSISTENCY FOR FA COMING FROM
DIFFERENT SOURCES
 TREATMENT INCLUDES SIZE REDUCTION &/OR
CLASSIFICATION

16. FLY ASH IN CONCRETE:
HYDRATION
 IT BEGINS WITH ADDITION OF WATER TO
CONCRETE & NEARLY 60%–65% HYDRATION
IS COMPLETE IN 28 DAYS
 MINERAL ADMIXTURES TAKE PART IN
HYDRATION REACTIONS
 AFFECT EARLY-AGE PROPERTIES:
WORKABILITY, SETTING, SHRINKAGE, ETC.,
BESIDES STRENGTH & DURABILITY OF
CONCRETE.

17. FLY ASH IN CONCRETE:
SETTING & HARDENING
• CALCIUM SILICATES FROM CEMENT REACT
WITH WATER TO FORM C-S-H & CH
• C-S-H IS PRINCIPAL STRENGTH GIVING
COMPUND
• C-S-H IN ACTS LIKE A “SPONGE,”
ABSORBING VARIETY OF IONS
• FULLY HYDRATED MASS OF CEMENT
CONTAINS MORE THAN 70% C-S-H

18. FLY ASH IN CONCRETE:
C-S-H

19. FLY ASH IN CONCRETE:
ADDITIONAL STRENGTH
WITH FLY ASH
 (REACTIVE SILICA IN FA) + (CALCIUM HYDROXIDE) =
ADDITIONAL C-S-H
 ADDITIONAL C-S-H LEADS TO REDUCTION IN
PERMEABILITY & IMPROVED DURABILITY
 HYDRATION OF FA DOES NOT BEGIN UNTIL ABOUT 7
DAYS
 LATE HYDRATION IMPORTANT FOR MASS CONCRETING
 SETTING DELAYED WITH LEVEL OF REPLACEMENT
 RATE OF STRENGTH DEVELOPMENT REMAINS
APPROPRIATE UP TO A REPLACEMENT LEVEL OF 60%

20. FLY ASH IN CONCRETE:
STRENGTH & DURABILITY
 STRENGTH IS COMBINATION OF THREE
FACTORS:
STRENGTH = DILUTION + PHYSICAL + CHEMICAL
 PHYSICAL EFFECT IS INCREASE IN STRENGTH
DUE TO FILLER EFFECT
 CHEMICAL EFFECT IS INCREASE IN STRENGTH
DUE TO POZZOLANIC REACTION
 IMPROVED INTERFACIAL TRANSITION ZONE
(ITZ) MICROSTRUCTURE

21. FLY ASH IN CONCRETE:
IMPORTANCE OF CURING
 IMPORTANT FOR DEVELOPMENT OF STRENGTH &
DURABILITY PROPERTIES
 EARLY & LONG TERM CURING IS BENEFICIAL
 PREVENTION OF MOISTURE LOSS IMPORTANT: (a)
WHEN W/C RATIO IS LOW, (b) WHEN CEMENT HAS A
HIGH RATE OF STRENGTH DEVELOPMENT & (c) WHEN
CONCRETE CONTAINS MINERAL ADMIXTURES
 MOISTURE LOSS FROM CONCRETE SURFACE
SPECIALLY FOR THIN ELEMENTS, RELATIVELY HIGH
IN HOT, DRY CLIMATE

22. FLY ASH IN CONCRETE:
DURABILITY AGAINST
CARBONATION
• CARBONATION REFERS TO PRECIPITATION OF
CALCITE (CaCO3) THRU REACTION OF PENETRATING
ATMOSPHERIC CO2, WITH CALCIUM HYDROXIDE IN
PORE SOLUTION
• MAIN CONSEQUENCE OF CARBONATION IS DROP OF
pH OF PORE SOLUTION OF CONCRETE FROM
STANDARD VALUES OF 12.5–13.5, TO A VALUE OF
ABOUT 8.3, SO THAT PASSIVE LAYER THAT USUALLY
COVERS & PROTECTS REINFORCING STEEL AGAINST
CORROSION BECOMES UNSTABLE
• EARLY & LONGER CURING PRODUCES BETTER
CARBONATION RESISTANCE, ESPECIALLY IN
CONCRETE WITH MINERAL ADMIXTURES

23. FLY ASH IN CONCRETE:
CARBONATION LEADS TO CORROSION
CARBONATION & SUBSEQUENT CORROSION OF
REINFORCEMENT

24. FLY ASH IN CONCRETE
DURABILITY AGAINST AAR
• AGGREGATES CONTAINING REACTIVE MINERALS REACT WITH
SOLUBLE ALKALIES IN CONCRETE & SOMETIMES RESULT IN
EXPANSION, CRACKING OF CONCRETE STRUCTURES
• STRUCTURES IN DIRECT CONTACT WITH WATER, SUCH AS DAMS
AND BRIDGES, ARE MORE SUSCEPTIBLE TO AAR
• CONDITIONS TO INITIATE & PROPAGATE AAR: (A) CRITICAL
QUANTITY OF REACTIVE AGGREGATE, (B) SUFFICIENT ALKALI IN
CONCRETE & (C) SUFFICIENT MOISTURE (.) ALL THREE
CONDITIONS MUST PREVAIL TOGETHER
• MINERAL ADMIXTURES REPLACING CEMENT, SUCH AS BFS, FA &
NATURAL POZZOLANS, MITIGATE OR ELIMINATE AAR IN CONCRETE
• TOTAL ALKALI CONTENT OF CONCRETE & LEVEL OF CEMENT
REPLACEMENT BY MINERAL ADMIXTURES ARE KEY FACTORS
GOVERNING EXPANSION OF CONCRETE

25. FLY ASH IN CONCRETE
CRACKING DUE TO AAR
CONCRETE PAVEMENT CRACKED DUE TO AAR

26. FLY ASH IN CONCRETE
DURABILITY AGAINST
CORROSION
• REINFORCING STEEL, SURROUNDED BY ALKALINE ENVIRONMENT IN
CONCRETE STRUCTURE, IS PROTECTED FROM ATTACK OF AGGRESSIVE
AGENTS BY THE PASSIVE IRON OXIDE FILM FORMED ON ITS SURFACE
• WHEN CHLORIDE IONS PENETRATE THROUGH POROUS CONCRETE & BUILD
UP AROUND REINFORCEMENT & ALKALINITY (pH) OF SURROUNDING PORE
SOLUTION FALLS SUBSTANTIALLY & PROTECTIVE IRON OXIDE FILM
DEPASSIVATES & CRACKS, EXPOSING STEEL
• EXPOSED STEEL GETS CORRODED IN PRESENCE OF WATER & OXYGEN,
RESULTING IN FORMATION OF EXPANSIVE CORROSION PRODUCTS (RUST)
THAT OCCUPY SEVERAL TIMES THE VOLUME OF ORIGINAL STEEL
CONSUMED
• EXPANSIVE CORROSION LEADS TO CRACKING & SPALLING OF CONCRETE
COVER
• MINERAL ADMIXTURES IMPART ENHANCED RESISTANCE TO CORROSION:
REDUCE DIFFUSION OF CHLORIDE IONS & OTHER DETERIORATING AGENTS,
ON ACCOUNT OF THE REFINEMENT OF PORE STRUCTURE

27. FLY ASH IN CONCRETE:
DURABILITY AGAINST
CORROSION
FLY ASH CONCRETE IS USED UNDER SEVERE EXPOSURE CONDITION SUCH AS
IN DECKS & PIERS OF SUNSHINE SKYWAY BRIDGE, TAMPA BAY, FLORIDA

28. FLY ASH IN CONCRETE:
DURABILITY AGAINST
EXTERNAL SULFATE ATTACK
• COMMONLY OBSERVED PHENOMENON, WHEN STRUCTURES ARE
EXPOSED TO SULFATE SOLUTIONS OR BUILT IN SULFATE BEARING SOIL
AND/OR GROUND WATER
• ALL COMMONLY OBTAINED WATER SOLUBLE SULFATES ARE
DELETERIOUS (Mg > Na > Ca) TO CONCRETE, BUT EFFECT IS SEVERE
WHEN IASSOCIATED WITH Mg CATIONS
• SULFATE IONS REACT WITH IONIC SPECIES OF PORE SOLUTION TO
PRECIPITATE GYPSUM, ETTRINGITE OR THAUMASITE OR A MIXTURE OF
THESE PHASES, DEPENDING UPON TEMPERATURE & OTHER
FAVORABLE CONDITIONS
• PRECIPITATION OF THESE SOLID PHASES LEADS TO STRESS WITHIN
CONCRETE INDUCING EXPANSION, STRENGTH LOSS, SPALLING &
SEVERE DEGRADATION
• APPLICATION OF PROTECTIVE COATING, LIKE EPOXY-BASED COATING,
IS ALSO RECOMMENDED ON CONCRETE SURFACE EXPOSED TO MgSO4
ENVIRONMENT

29. FLY ASH IN CONCRETE:
DURABILITY AGAINST
INTERNAL SULFATE ATTACK
• INTERNAL SULFATE ATTACK (ISA) OR DELAYED ETTRINGITE FORMATION
(DEF)
• FORMATION OF EXPANSIVE ETTRINGITE IN HYDRATED CONCRETE AFTER
HARDENING IS SUBSTANTIALLY COMPLETE
• OCCURS WHEN ETTRINGITE, FORMED DURING HYDRATION, IS DECOMPOSED
& SUBSEQUENTLY FORMED AGAIN IN HARDENED CONCRETE
• MOSTLY OBSERVED IN PRECAST CONCRETE PRODUCTS, CURED AT
ELEVATED TEMPERATURE
• TWO CONDITIONS PROMOTING DEF: (A) INTERNAL TEMPERATURE ABOVE
70°C, TO DECOMPOSE ETTRINGITE FORMED DURING INITIAL HYDRATION, (B)
AFTER RETURNING TO NORMAL TEMPERATURE, CONCRETE IS EXPOSED TO
MOIST OR WET SURROUNDINGS
• ADDITION OF MINERAL ADMIXTURES TO CONCRETE REDUCES DEF
• FA AT HIGHER REPLACEMENT LEVELS FOUND EFFECTIVE IN CONTROLLING
DEF

30. FLY ASH IN CONCRETE
HIGH VOLUME FLY ASH CONCRETE
(HVFAC)
• TERM COINED BY MALHOTRA et.al. in 1980
• CEMENT CONTENT < 200 kg / cu. M
• WATER CONTENT < 130 kg / cu. M
• FA CONTENT > 50% CEMENT REPLACEMENT BY MASS
• HRWRA REQUIRED FOR HIGH SLUMP (150-200 mm) &
HIGH EARLY STRENGTH (>30 MPa) & w/b RATIO: O.3
• HRWRA NOT REQUIRED FOR LOWER SLUMP, LOWER
STRENGTH & w/b RATIO: 0.4
• AEA REQUIRED UNDER FREEZE-THAW CONDITIONS TO
MAINTAIN AIR-VOID RATIO

31. HVFAC ROAD: FATEHPUR BERI
MUNICIPAL CORPORATION N DELHI (MCD)
(100 m LONG – 7 m WIDE)

32. HVFAC UNDERGROUND CONSTRUCTION
S-E ENTRANCE SUBWAY, RAJIV CHOWK , N DELHI
DELHI METRO RAIL CORPORATION (DMRC)

33. HVFAC MCD & DMRC CONSTRUCTIONS
EXPERIENCE
• USING ONLY HALF OF THE CONVENTIONAL OPC , SAVED GHG EMISSIONS,
NEARLY 200 Kg PER M3 OF CONCRETE USED
• LOWER EARLY COMPRESSIVE STRENGTH BUT VERY GOOD LATER-AGE
STRENGTH WHICH CONTINUES TO INCREASE OVER SEVERAL MONTHS
• PRACTICAL EXAMPLE FOR INCREASING ACCEPTANCE CRITERION TO 60-90 D,
WHEREVER STRUCTURE IS LOADED AT LATER AGE
• BETTER IN TERMS OF ELASTIC MODULUS, FLEXURAL, TENSILE & ABRASION
• LOWER PERMEABILITY & HENCE BETTER DURABILITY
• SETTING TIME AT DMRC PROJECT WAS UNDULY LONG, WHILE AT MCD IT WAS
QUITE LIKE PLAIN CONCRETE, SUGGESTING IMPORTANCE OF CHOOSING
CORRECT SUPERPLASTICIZER
• QUALITY CONTROL IMPORTANT IN HVFAC AS IN CONVENTIONAL CONCRETE

34. FLY ASH IN CONCRETE
FINE FA OR FFA
• ALSO TERMED AS ULTRA-FINE FA
• MEAN PARTICLE DIA OF
CONVENTIONAL FA: 20-30
MICRONS
• MEAN PARTICLE DIA OF FINE FA :
1-5 MICRONS
• LOW UNBURNED CARBON
• OBTAINED BY GRINDING &/OR
AIR SEPARATION

35. MICROSTRUCTURE: TRADITIONAL VERSUS HPC
C3A + GYPSUM + WATER = ETTRINGITE = 3CaO.Al2O3.3CaSO4.32H2O

36. FLY ASH IN CONCRETE
HPC WITH FFA
• HIGH STRENGTH: 70-140 MPa @ 28-91 D
• HIGH EARLY STRENGTH: 20-30 MPa @ 3-12 h
OR 1-3 D
• HIGH EARLY FLEXURAL STRENGTH: 2-4 MPa
@ 3-12 h OR 1-3 D
• HIGH MODULUS OF ELASTICITY > 40 GPa
• ABRASION RESISTANCE: 0-1 mm DEPTH OF WEAR
• LOW PERMEABILITY: 500-2000 COULOMBS
• CHLORIDE PENETRATION < 0.07% Cl AT 6 MONTHS
• LOW WATER ABSORPTION: 3-5%

37. FLY ASH IN CONCRETE
SF & FFA COMPARED
• CONCRETE CONTAINING FFA
COULD BE PRODUCED WITH ONLY
50% OF HIGH-RANGE WATER
REDUCER (HRWR) DOSAGE IN
COMPARISON TO SILICA FUME
(SF) CONCRETE

38. TRAINING COURSE

39. TRAINING COURSE
TWO DAY TRAINING COURSE
ON
DURABLE, HIGH PERFORMANCE
CEMENT & CONCRETE
WITH
MINERAL & CHEMICAL
ADMIXTURES

40. TRAINING COURSE
CONTENTS
 APPLICATION OF MINERAL ADMIXTURES:
FA, BFS, SF, MK RHA
 APPLICATION OF CHEMICAL ADMIXTURES
& SUPER PLASTICISERS
 HIGH PERFROMANCE CONCRETE:
HIGH STRENGTH, SCC, RCC, LIGHTWEIGHT,
PERVIOUS, HVFAC
 GROUP DISCUSSIONS, CASE STUDIES &
VIDEOS
 DETAILS: http://www.drjdbapat.com

41. TRAINING COURSE
WHO SHOULD ATTEND
 ENGINEERS WORKING AT CONSTRUCTION
SITE
 ENGINEERS WORKING WITH CEMENT,
CONCRETE INDUSTRY
 ENGINEERS WORKING WTH MANUFACTURERS
AND SUPPLIERS OF CHEMICAL ADMIXTURES
AND MINERAL ADMIXTURES
 ENGINEERS WORKING ON PRODUCT
DEVELOPMENT
 STUDENTS/RESEARCHERS
 DETAILS: http://www.drjdbapat.com

42. TRAINING COURSE
FLEXIBILITY
CONTENTS: CHOOSE AS PER YOUR
REQUIREMENT
DURATION: 1-2 DAYS
VENUE: PUNE OR YOUR HEAD OFFICE,
PLANT OR CONSTRUCTION SITE
DETAILS: http://www.drjdbapat.com

43. FLY ASH IN CONCRETE:
ACKNOWLEDGEMENT
• I THANKFULLY ACKNOWLEDGE THAT WHILE MAKING
THIS PRESENTATION, I HAVE FREELY DRAWN UPON
THE INFORMATION PUBLISHED IN THE FOLLOWING
BOOK:
MINERAL ADMIXTURES IN CEMENT AND CONCRETE
AUTHOR: JAYANT D. BAPAT
PUBLISHER: CRC PRESS, TAYLOR & FRANCIS GROUP,
USA