This is a presentation by Dr. J.D. Bapat and independent professional in India at the 3rd Annual East Africa Cement Concrete and Energy Summit

1. DURABLE & SUSTAINABLE CONCRETE
WITH
MINERAL ADMIXTURES
by
Dr J D Bapat
http://www.drjdbapat.com
3rd EAST AFRICA CEMENT, CONCRETE
AND ENERGY SUMMIT
ADDIS ABABA
1-2 AUGUST 2018

2. ACKNOWLEDGEMENT
• WITH SINCERE THANKS TO THE PUBLISHER:
• I ACKNOWLEDGE THAT WHILE PREPARING THIS
PRESENTATION I HAVE USED INFORMATION GIVEN IN MY
BOOK:
“MINERAL ADMIXTURES IN CEMENT AND CONCRETE”
CRC PRESS – TAYLOR & FRANCIS GROUP

3. MINERAL ADMIXTURES
 PULVERISED FUEL ASH (PFA)
 BLAST FURNACE SLAG (BFS)
 SILICA FUME (SF)
 RICE HUSK ASH (RHA)
 METAKAOLIN

4. MINERAL ADMIXTURES
 PULVERISED FUEL ASH (PFA)

5. PULVERISED FUEL ASH
ENERGY & GHG
CEMENT TYPE THERMAL ENERGY ELECTRICAL ENERGY
PC 100 100
PPC (15%) 84 89
PSC (50%) 47 79
• IDEAL ENERGY CONSUMPTION FOR A NEW LARGE CAPACITY PLANT:
THERMAL: 680–720 kcal/kg & ELECTRICAL: 72–74 kwh/t
• CEMENT INDUSTRY CONTRIBUTES 5% OF TOTAL ANTHROPOGENIC CO2
EMISSIONS GLOBALLY
• WBCSD TARGET: REDUCTION IN CO2 EMISSION BY A FACTOR OF 2 BY 2050
FROM THEIR 1990 LEVELS
• TECHNOLOGICAL SHIFT: CHANGES IN CONCRETE RAW MATERIALS, MIX
DESIGN, NEW BUILDING TECHNIQUES & USING LESS MATERIALS

6. PULVERISED FUEL ASH (PFA)
 PULVERISED FUEL ASH OR FLY ASH IS
INORGANIC MATTER LEFT AFTER COAL
COMBUSTION, WHICH GETS COLLECTED, IN FINE
FORM, IN ELECTROSTATIC PRECIPITATORS (ESP)
OF THERMAL POWER STATIONS
 ADDITION OF PFA TO CEMENT OR CONCRETE
REDUCES CLINKER PRODUCTION & CONTRIBUTES
TO LONG TERM STRENGTH & DURABILITY OF
CONCRETE

7. PULVERISED FUEL ASH
PHYSICAL
 ASTM C618 CLASSIFICATION:
CLASS F: OBTAINED BY BURNING ANTHRACITE COAL: POZZOLANIC
CLASS C: OBTAINED BY BURNING LIGNITE COAL: POZZOLANIC &
CEMENTITIOUS
 PHYSICAL CHARACTERISTICS: NAMELY, SHAPE, SPECIFIC GRAVITY,
SIZE AND FINENESS, & UNBURNED CARBON CONTENT, AFFECT PFA
PERFORMANCE IN CONCRETE
 POZZOLANIC REACTIVITY: AFFECTED BY FINENESS THAN GLASS
CONTENT (.) GRINDING OR SIZE REDUCTION OPERATION IMPROVES
POZZOLANIC ACTIVITY OF PFA

8. PULVERISED FUEL ASH
ASTM
 FAS: Fe2O3 + Al2O3 + SiO2 (.) CLASS F: FAS > 70% (.)
CLASS C: FAS > 50%
• RETENTION ON 45 MICRON (325 MESH) SIEVE (%, MAX):
34%

9. PULVERISED FUEL ASH
PARTICLE SHAPE
SPHERICAL CENOSPHERES

10. PULVERISED FUEL ASH
PARTICLE SHAPE
PLEROSPHERES: CRACKED SPHERES

11. PULVERISED FUEL ASH
PARTICLE SHAPE COMPARED WITH PC

12. PULVERISED FUEL ASH
PHYSICAL
 PARTICLE SIZE RANGE: 1 TO 100 MICRON
 UNDER 10 MICRON: EARLY, 7 & 28 D, STRENGTH
 10 TO 45 MICRON: REACT SLOWLY & CONTRIBUTE TOWARD LATE
STRENGTH , UP TO 1 YEAR
ABOVE 45 MICRON: INERT & ACT AS FINE SAND OR FILLER
 UNBURNED CARBON (UBC) PARTICLES:
 CONTRIBUTE MAX TO LOSS ON IGNITION
 INFLUENCE CEMENT WATER DEMAND FOR STANDARD
CONSISTENCY
 STRONG AFFINITY TOWARD ORGANIC CHEMICAL ADMIXTURES,
SUCH AS AIR-ENTRAINING AGENTS (AEA)
 PFA WITH LESS THAN 3%–4% CARBON: SAFE TO USE

13. PULVERISED FUEL ASH
CHEMICAL & MINERALOGICAL
 HETEROGENEOUS MIXTURE OF COMPLEX
ALUMINOSILICATE GLASSES & SOME CRYSTALLINE
CONSTITUENTS
 OXIDE COMPOSITION OF PFA EXHIBITS SUBSTANTIAL
REGIONAL VARIATION
PFA COMING FROM SAME SOURCE (NAMELY, THERMAL
POWER STATION) MAY ALSO SHOW VARIATION IN
COMPOSITION

14. PULVERISED FUEL ASH
CHEMICAL & MINERALOGICAL
 IN PORTLAND CEMENT THERE IS CLOSE RELATIONSHIP
BETWEEN CHEMICAL & MINERALOGICAL COMPOSITION
 IN MINERAL ADMIXTURE THERE IS NO RELATIONSHIP
BETWEEN CHEMICAL & MINERALOGICAL COMPOSITION

15. PULVERISED FUEL ASH
FLUIDISED BED
 LOW TEMP: IN COMPARISON TO CONVENTIONAL
PULVERIZED COAL FIRED SYSTEM, FLUIDISED BED SYSTEM
HAS A RELATIVELY LOW COMBUSTION TEMPERATURE,
TYPICALLY IN RANGE 800°C–900°C
 NON-ASTM: PFA FROM FLUIDISED BED CANNOT BE
CLASSIFIED AS ASTM CLASS F OR C, IN MANY CASES,
BECAUSE OF LOW FAS (FERRIC OXIDE + ALUMINA + SILICA
CONTENT) & HIGH SO3 CONTENT

16. PULVERISED FUEL ASH
CO-COMBUSTION
PFA FROM CO-COMBUSTION OF BITUMINOUS COAL &
PETCOKE
 ADDS MORE UBC & COARSENESS TO PFA
 NO LEACHING OF NICKEL & VANADIUM IN ENVIRONMENT
 USE OF PETCOKE PFA HAS NO DETRIMENTAL EFFECTS ON
EITHER STRENGTH DEVELOPMENT OR AIR ENTRAINMENT
COMPARED TO BITUMINOUS COAL PFA

17. PULVERISED FUEL ASH
ULTRA FINE FA OR UFFA
ULTRA-FINE FA
 MEAN PARTICLE DIA OF CONVENTIONAL FA: 5-30 MICRONS
 MEAN PARTICLE DIA OF ULTRA-FINE FA : 1-5 MICRONS
 LOW UNBURNED CARBON

18. PULVERISED FUEL ASH
UFFA REMOVES FA LIMITATIONS
 HIGHER EARLY STRENGTH & HIGHER HEAT OF HYDARTION
DUE TO FASTER & COMPLETE REACTION
 LOW REPLACEMENT: 5-15% REPLACEMENT UFFA MAKES
SUBSTANTIAL CONTRIBUTION TO CONCRETE STRENGTH &
PERMEABILITY REDUCTION
 BETTER DURABILITY: WITH LESS CARBON & FINER
PARTICLES REACTING COMPLETELY
 CONCRETE DURABILITY PROPERTIES LIKE RESISTANCE TO
ALKALI-AGGREGATE REACTION, SULFATE ATTACK,
CORROSION ARE ENHANCED BY UFFA

19. PULVERISED FUEL ASH
SPECIFYING FOR CONCRETE
 LARGER QUANTITIES OF FA (>25) DELAY SETTING & EARLY
STRENGTH, BUT CAN BE TACKLED EFFECTIVELY WITH SP
 LOI: 2-4% DOES NOT ALWAYS ELIMINATE PROBLEM OF AIR
ENTRAINING AGENT, WHEN CARBON PARTICLES ARE FINE
 WHERE POSSIBLE, SPECIFYING 56 DAY STRENGTH INSTEAD OF
28 DAY, CAN RESULT IN BETTER OPTIMISED MIXTURE
 FOR REACTIVE AGGREGATES, BETTER TO PERFORM STANDARD
EXPANSION TESTS TO DETERMINE LIMIT OF FA ADDITION
 TO CONTROL ASR, BETTER TO KEEP FA ALKALI < 5% Na2O eq.
(IS 3812 SPECIFIES < 1.5%)

20. PULVERISED FUEL ASH
SPECIFYING FOR CONCRETE
 CLORIDE RESISTANCE: PERFORM RCPT AS PER ASTM C1202 TO
FIND FA CONTENT FOR RCPT VALUE OF 1500-2000 COULOMBS (.) 56
DAY STRENGTH ADVISABLE
 IS 456-2000: MAX ACID SOLUBLE Cl IN RCC = 0.6 Kg/M3
CONCRETE
SULPHATE RESISTANCE: IS 456 SPECIFIES MAX 4% BY MASS OF
CEMENT IN CONCRETE MIX
 PERFORM TEST AS PER ASTM C1012 TO FIND OPTIMUM FA FOR
SULPHATE RESISTANCE (.) ONLY DISADVANTAGE IS TEST TAKES
LONG TIME: 6 MONTHS TO 1 YEAR

21. PULVERISED FUEL ASH
ADDITION TO CEMENT & CONCRETE
PFA IS ADDED DIRECTLY TO RMC AT BATCHING UNIT,
INTER-GROUND WITH CEMENT CLINKER, OR BLENDED WITH
PC AT CEMENT PLANT TO PRODUCE BLENDED CEMENT
BLENDED CEMENT: MOST NATIONAL STANDARDS ALLOW
ADDITION OF PFA TO CEMENT UP TO THE EXTENT OF 35%–
40%, TO MANUFACTURE BLENDED CEMENT

22. MINERAL ADMIXTURES
 BLAST FURNACE SLAG (BFS)

23. BLAST FURNACE SLAG (BFS)
GGBS
GROUND GRANULATED BFS OR GGBS
 PRODUCED BY QUENCHING OF MOLTEN SLAG COMING FROM
BLAST FURNACE IN PARTICLE SIZE MOSTLY PASSING 4.75 mm
SIEVE & MAX UP TO 10 mm
1 t OF PIG IRON GENERATES 250–350 kg OF SLAG
BRITISH STANDARD SPECIFICATION FOR GGBS (BS 6699), FOR
USE WITH PORTLAND CEMENT, REQUIRES GLASS CONTENT >
67%
 GRINDING OF GRANULATED BFS, LEADS TO PRODUCTION OF
GROUND GRANULATED BLAST FURNACE SLAG OR GGBS

24. BLAST FURNACE SLAG (BFS)
GGBS
 LOWER SPECIFIC GRAVITY: IN RANGE OF 2.9–3.0, LOWER
IN COMPARISON WITH PC (3.0 - 3.2)
 FINENESS & STRENGTH CHARACTERISTICS OF GGBS ARE
CONVENTIONALLY CORRELATED
 ACTIVITY OF GGBS IS PROPORTIONAL TO THE GLASS
CONTENT

25. BLAST FURNACE SLAG (BFS)
GGBS
2.4

26. BLAST FURNACE SLAG (BFS)
QUALITY CONTROL
 ASTM C-989-09: SPECIFIES THREE GRADES OF GGBS BY
STRENGTH: GRADE 80, 100 & 120
 GRADE 120: REPRESENTS HIGHEST STRENGTH
 GRADE IS DETERMINED BY STRENGTH OF MORTAR, WHEN GGBS
IS MIXED WITH EQUAL MASS OF PC
 THREE GRADES: 80, 100 & 120 CLASSIFIED ACCORDING TO SLAG
ACTIVITY INDEX, BASED ON STRENGTH
 SLAG ACTIVITY INDEX (%) = (STRENGTH OF
SLAG+CEMENT)/(STRENGTH OF CEMENT)X100 = (SP/P)100

27. BLAST FURNACE SLAG (BFS)
SPECIFYING FOR CONCRETE
 TEMP INFLUENCES SETTING OF GGBS CONCRETE
 MASS CONCRETING: TEMP RISE REDUCES WITH INCREASING
GGBS
 CARBONISATION: INCREASES WITH GGBS CONTENT BUT
DEPENDS UPON TEMP & RH (.) EFFECTIVELY CONTROLLED
WITH CURING
 HIGH RESISTANCE TOWARDS Cl ION PENETRATION DUE TO
ION BINDING CAPACITY
 SULPHATE RESISTANCE: INCREASES WITH GGBS > 50%
 BETTER RESISTANCE TOWARDS ACID ATTACK

28. BLAST FURNACE SLAG (BFS)
ADDITION TO CEMENT & CONCRETE
 PARTIAL REPLACEMENT FOR CEMENT IN FOLLOWING TWO WAYS:
 CEMENT MANUFACTURING UNIT:
 SEPARATE GRINDING OF BFS & CLINKER & MIXING ALONG
WITH GYPSUM IN A MECHANICAL BLENDING UNIT
 INTERGRINDING OF BFS, CLINKER & GYPSUM
 CONCRETE MAKING SITE: GGBS OF DESIRED FINENESS
ADDED TO CONCRETE, TO REPLACE CEMENT PARTIALLY
 MOST WORLD STANDARDS LIMIT THE ADDITION OF BFS IN SLAG
CEMENT UP TO 70%
 HIGHER REPLACEMENTS ADVANTAGEOUS FOR CERTAIN
APPLICATIONS

29. HYDRATION, STRENGTH & DURABILITY
OF
CONCRETE

30. HYDRATION
 HYDRATION: COMBINATION OF ALL CHEMICAL & PHYSICAL PROCESSES
OCCURING, AFTER CONTACT OF ANHYDROUS SOLID WITH WATER
 HYDRATION PERIODS:
 WORKABILITY PERIOD: 1–3 h: VERY LOW RATE (DORMANT) HYDRATION:
WETTING, MIXING, TRANSPORTING, AGITATING, PLACING & FINISHING OF
CONCRETE
 SETTING PERIOD: MIN IST > 60 min & MAX. FST RANGE 3–5 h: ACTIVE
REACTION: CUIRING CAN START AFTER FST
 HARDENING PERIOD: ABOUT 28 DAY: DECELERATION & SLOW REACTION:
CURING TO CONTINUE FOR 7 TO 14 DAYS

31. HYDRATION
WITH MINERAL ADMIXTURES
 FIVE PRINCIPAL MINERAL ADMIXTURES: PFA, BFS, SF, RHA, & MK,
ARE EITHER POZZOLANIC OR CEMENTITIOUS
 CH REACTS WITH BOTH POZZOLANIC & CEMENTITIOUS
ADMIXTURES TO FORM ADDITIONAL CEMENTITIOUS PRODUCTS
 ADMIXTURE HYDRATION PRODUCES MORE C-S-H, WHICH LEADS
TO HIGHER STRENGTH
 HYDRATION DOES NOT BEGIN UNTIL AMORPHOUS MINERALS
(GLASS) DISSOLVES & REACTS WITH CH
 PFA ADDITION: WORKABILITY IMPROVES OR WATER
REQUIREMENT DECREASES, FOR GIVEN WORKABILITY
 IST & FST INCREASE: WITH REPLACEMENT BUT STRENGTH
DEVELOPMENT REMAINS APPROPRIATE
 CURING: PROVIDE PROPER CURING TEMPERATURE & MOISTURE
FOR UP TO A WEEK

32. STRENGTH & DURABILITY
 DURABILITY: ABILITY OF STRUCTURE TO RESIST WEATHERING
ACTION, CHEMICAL ATTACK & ABRASION, MAINTAINING MIN
STRENGTH & OTHER DESIRED ENGINEERING PROPERTIES
 DESIGNING FOR STRENGTH & DURABILITY SYNONYMOUS TO
DESIGNING FOR SUSTAINABILITY
 NATIONAL STANDARDS MOSTLY PRESCRIPTIVE , DEFINING
EXPOSURE CONDITIONS, DESIGN PROCEDURE, BUILDING
MATERIALS & THEIR APPLICATION, NOT ASSURING MIN SERVICE
LIFE OF STRUCTURE, WHEN SPECIFICATIONS ARE FOLLOWED
 DURABILITY DEPENDS UPON BOTH EXPOSURE ENVIRONMENT &
QUALITY OF CONCRETE

33. STRENGTH & DURABILITY
DESIGNING FOR DURABILITY
 PERMEABILITY IS THE SINGLE MOST IMPORTANT CRITERION FOR
DURABILITY
 TWO MAJOR FAULTS IN CONCRETE CONSTRUCTION THAT CAN
LEAD TO THE LOSS OF DURABILITY: INADEQUATE COVER TO
REINFORCEMENT & INADEQUATE COMPACTION OF COVER
CONCRETE
 QUALITY CONTROL NORMS FOR CONSTRUCTION MATERIALS
WELL ESTABLISHED, BUT PRACTICALLY NONEXISTENT FOR
CONSTRUCTION PROCESS

34. STRENGTH & DURABILITY
CONCRETE STRENGTH
STRENGTH OF CONCRETE CONTAINING MINERAL ADMIXTURES,
f(ADMIXTURE)
f(ADMIXTURE) = f(DILUTION) + f(PHYSICAL) + f(CHEMICAL)
 f(DILUTION) = REDUCED STRENGTH PROPORTIONAL TO
AMOUNT OF CEMENT IN MIXTURE
 f(PHYSICAL) = INCREASE IN STRENGTH DUE TO PHYSICAL
EFFECT OR HETEROGENEOUS NUCLEATION & FILLER EFFECT
DUE TO MINERAL ADMIXTURE
 f(CHEMICAL): INCREASE IN STRENGTH RELATED TO
POZZOLANIC REACTION

35. STRENGTH & DURABILITY
INTERFACIAL TRANSITION ZONE
(ITZ)
0% SF 10% SF
SEM IMAGES OF CONCRETE ITZ MICROSTRUCTURE AT 28 DAYS WITH 0%
& 10% BY MASS OF SF. 7.6

36. STRENGTH & DURABILITY
REDUCED PERMEABILITY
CAPILLARY PORES INTERCONNECTED CAPILLARY PORES PARTIALLY BLOCKED
Neville and Brooks 1987

37. STRENGTH & DURABILITY
REDUCED TEMPERATURE RISE

38. STRENGTH & DURABILITY
IMPORTANCE OF CURING
 CURING: IS A PROCESS OF PREVENTING LOSS OF MOISTURE FROM
CONCRETE, WHILE MAINTAINING SATISFACTORY TEMPERATURE REGIME
 EARLY & LONG TERM CURING IS BENEFICIAL FOR DEVELOPMENT OF
CONCRETE PROPERTIES
MOISTURE LOSS PREVENTION IMPORTANT WHEN w/c RATIO IS LOW,
WHEN CEMENT HAS A HIGH RATE OF STRENGTH DEVELOPMENT & WHEN
CONCRETE CONTAINS MINERAL ADMIXTURES
 ADEQUATE & CONTINUOUS SUPPLY OF WATER IS NECESSARY FOR
LONG-TERM STRENGTH DEVELOPMENT & IMPROVED DURABILITY
PERFORMANCE OF CONCRETE WITH MINERAL ADMIXTURES

39. STRENGTH & DURABILITY
ROLE OF MINERAL ADMIXTURE
CONCRETE
DETERIORATION

40. STRENGTH & DURABILITY
ROLE OF MINERAL ADMIXTURE
 REDUCE CONCRETE DETERIORATION BY: (A) CARBONATION, (B) ASR, (C)
CORROSION OF REINFORCEMENT, (D) SULFATE ACTION, (E) DECALCIFICATION OR
LEACHING & (F) FROST ACTION
WHEN MINERAL ADMIXTURE IS USED:
(A) FIXES ALKALI: ABOUT 95% ALKALIS FIXED THROUGH ADSORPTION OR SOLID
SOLUTION
(B) SECONDARY C-S-H: FORMED BY SECONDARY HYDRATION, FILLS UP PORES
IN HARDENED CEMENT PASTE, MAKING PORE STRUCTURE FINER & DENSER
(C) REDUCES C3A: PREVENTS SULFATE ATTACK
(D) CH REDUCTION: LEADS TO REDUCTION IN CaSO4 GENERATION & HELPS
MITIGATE SULFATE ATTACK
(E) PERMEABILITY REDUCTION THRU PACKING EFFECT OF UNREACTED
PARTICLES
(F) CHLORIDE BINDING: SOME MINERAL ADMIXTURES HAVE GREATER CHLORIDE-
BINDING CAPACITY IN COMPARISON TO PC

41. STRENGTH & DURABILITY
CARBONATION
 CARBONATION: PRECIPITATION OF CALCITE (CaCO3) & OTHER
CO2-BASED SOLID COMPUNDS, THROUGH REACTION OF
PENETRATING ATMOSPHERIC CO2 WITH Ca IONS IN PORE
SOLUTION
 pH DROP: DROP OF pH OF PORE SOLUTION OF CONCRETE
FROM 12.5–13.5 TO ABOUT 8.3, SO THAT PASSIVE IRON OXIDE
LAYER THAT USUALLY COVERS & PROTECTS REINFORCING STEEL
AGAINST CORROSION, BECOMES UNSTABLE
 C-S-H LOSS: WITH CONSTANT CO2 DIFFUSION, CH GETS
FURTHER DEPLETED & CALCIUM FROM C-S-H ALSO REACTS,
LEADING TO LOSS OF STRENGTH, VOLUMETRIC DECREASE
(SHRINKAGE) & CRACKING & INCREASE IN CONCRETE POROSITY

42. STRENGTH & DURABILITY
CARBONATION
DAMAGE CAUSED TO STRUCTURE DUE TO CARBONATION
& SUBSEQUENT CORROSION OF REINFORCEMENT
7.12

43. STRENGTH & DURABILITY
CARBONATION
 INCREASES WITH CO2 CONCENTRATION IN SURROUNDINGS
 NORMAL ATMOSPHERIC CONDITIONS & RH OF 50%–80%
OPTIMUM
 JAN BIJEN et.al.: LARGE SCALE STUDY ON DURABILITY OF
STRUCTURES BUILT ALONG DUTCH COAST, WITH BFS CONCRETE (.)
STRUCTURES INCLUDED SLUICES, PIERS & QUAYS, RANGING IN
AGE FROM 3 TO 63 YRS (.) IN 48 OUT OF 51 STRUCTURES,
CARBONATION DEPTH WAS < 5 mm
 EARLY & LONGER CURING GIVES BETTER CARBONATION
RESISTANCE, ESPECIALLY IN CONCRETE WITH MINERAL
ADMIXTURES

44. STRENGTH & DURABILITY
ALKALI-AGGREGATE REACTIONS
(AAR)
AAR: WHEN AGGREGATES CONTAINING CERTAIN DOLOMITIC (Ca +
Mg) OR SILICEOUS MINERALS REACT WITH SOLUBLE ALKALIES IN
CONCRETE
 SOMETIMES RESULT IN DETRIMENTAL EXPANSION, CRACKING &
PREMATURE LOSS OF SERVICEABILITY OF CONCRETE
STRUCTURES AFFECTED
 ALL KINDS OF CONCRETE STRUCTURES MAY BE AFFECTED (.)
STRUCTURES IN DIRECT CONTACT WITH WATER, SUCH AS DAMS &
BRIDGES, ARE PARTICULARLY SUSCEPTIBLE TO AAR
 TWO TYPES OF AAR: (A) ALKALI–CARBONATE REACTION (ACR) &
(B) ALKALI–SILICA REACTION (ASR)

45. STRENGTH & DURABILITY
ALKALI-AGGREGATE REACTIONS
(ACR & ASR)
ALKALI-CARBONATE REACTION (ACR)
 PROCESS OF DEGRADATION OF CONCRETE CONTAINING
DOLOMITIC (DOLOMITE: CaCO3.MgCO3 ) AGGREGATE
SEPARATION OF CALCIUM & MAGNESIUM COMPOUNDS TAKES
PLACE
ALKALI-SILICA REACTION (ASR)
 INCREASED REACTIVITY OR INSTABILITY OF AMORPHOUS,
SILICA FOUND IN AGGREGATE ROCKS
 ASR MAY BE OBSERVED AFTER 5–25 YEARS OF CONSTRUCTION &
MAY AFFECT ANY CONCRETE STRUCTURE

46. STRENGTH & DURABILITY
ALKALI-AGGREGATE REACTIONS
(ACR & ASR)
CONCRETE PAVEMENT CRACKED DUE TO ASR
7.19

47. STRENGTH & DURABILITY
ALKALI-AGGREGATE REACTIONS
 INITIATION & PROPAGATION: THREE NECESSARY CONDITION: (A)
CRITICAL QUANTITY OF REACTIVE AGGREGATE, (B) SUFFICIENT ALKALI IN
CONCRETE & (C) SUFFICIENT MOISTURE
 ALKALI CONTENT IN CEMENT EXPRESSED AS “SODIUM OXIDE
EQUIVALENT”
(MASS PERCENT) Na2Oeq = Na2O + 0.658 K2O
 HARMLESS ALKALI CONTENT: < 0.6% Na2Oeq IN CEMENT OR < 1.8 Kg/m3
IN CONCRETE
 ASTM C1260, ACCELERATED MORTAR BAR TEST (AMBT), IS MOST WIDELY
USED TEST METHOD
 MINERAL ADMIXTURES REPLACING CEMENT, SUCH AS BFS, PFA &
NATURAL POZZOLANS, MITIGATE OR ELIMINATE AAR IN CONCRETE
 HIGHER REPLACEMENTS GOOD: SIGNIFICANT REDUCTION IN AAR
EXPANSION ACHIEVED FOR PFA (>25%) OR BFS (>40%) OR COMBINATION OF
BOTH

48. STRENGTH & DURABILITY
ALKALI-AGGREGATE REACTIONS
ASR: ALKALI–SILICA GEL SEEN AS DARK RIM AROUND AGGREGATE PARTICLE
7.21

49. STRENGTH & DURABILITY
CORROSION
CHLORIDE ATTACK & CORROSION OF REINFORCEMENT
 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 VOLUME OF
ORIGINAL STEEL CONSUMED
 EXPANSIVE CORROSION PRODUCTS CREATE TENSILE STRESS IN
CONCRETE SURROUNDING CORRODING STEEL REBAR, LEADING
TO CRACKING & SPALLING OF CONCRETE COVER

50. STRENGTH & DURABILITY
CORROSION
 AASHTO T259: 90-DAY SALT-PONDING TEST TO EVALUATE CHLORIDE
DIFFUSION COEFFICIENT, REQUIRES LONG-TERM PONDING (IN YEARS) TO
OBTAIN RELIABLE ESTIMATES OF CHLORIDE DIFFUSION COEFFICIENT
 RAPID CHLORIDE PERMEABILITY TEST (RCPT), ASTM C1202: DEVELOPED
TO NON-DESTRUCTIVELY OBTAIN INDICATION ON CHLORIDE PERMEABILITY
OF CONCRETE, IN A SHORT TIME PERIOD
 RCPT CORRELATES CONCRETE RESISTIVITY WITH PERMEABILITY
 MINERAL ADMIXTURES IMPART ENHANCED RESISTANCE TO DIFFUSION
OF CHLORIDE IONS & OTHER DETERIORATING AGENTS, ON ACCOUNT OF
REFINEMENT OF PORE STRUCTURE
 CORROSION INITIATION DELAYED & PROPAGATION EXTENDED
AASHTO: American Association of State Highway and Transport Officials

51. STRENGTH & DURABILITY
CORROSION
PERMEABILITY OF CONCRETE WITH PFA
7.25

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

53. STRENGTH & DURABILITY
CORROSION
HUNGRY HORSE DAM, ON MONTANA’S FLATHEAD RIVER (.) ONE
OF THE LARGEST CONCRETE-ARCH DAMS IN USA,
COMPLETED IN 1953, WAS BUILT WITH 120,000 T OF FLY ASH

54. STRENGTH & DURABILITY
EXTERNAL SULFATE ATTACK
 HIGH C3S & C3A CONTENT IN PC REDUCES RESISTANCE TO
SULFATE ATTACK
 PARTIAL REPLACEMENT OF PC WITH MINERAL ADMIXTURES
REDUCES C3S & C3A IN BLEND
 Na2SO4: CONCRETE WITH MINERAL ADMIXTURES SHOWS
LOWER EXPANSION
 MgSO4: CONCRETE WITH MINERAL ADMIXTURES SHOWS HIGHER
STRENGTH REDUCTION, IN COMPARISON TO THAT WITH PC
 NEGATIVE EFFECT OF MINERAL ADMIXTURES, DURING MgSO4
ATTACK OFTEN OFFSET BY REDUCED PERMEABILITY &
DENSIFICATION CAUSED BY THEIR USE
 APPLICATION OF PROTECTIVE COATING LIKE EPOXY
RECOMMENDED ON CONCRETE SURFACE EXPOSED TO MgSO4
ENVIRONMENT
7.29

55. STRENGTH & DURABILITY
EXTERNAL SULFATE ATTACK
 Al2O3 (ALUMINA) CONTENT OF BFS IS SAID TO LOWER ITS
SULFATE RESISTANCE (.) HOWEVER THERE IS NO DIRECT
RELATIONSHIP, AS A PART OF Al2O3 IS TAKEN UP IN C-S-H
STRUCTURE, WHERE IT IS LESS PRONE TO SULFATE ATTACK
 BLENDED CEMENT WITH > 60% BFS, SHOWS MODERATE
TO GOOD SULFATE RESISTANCE, IRRESPECTIVE OF Al2O3
CONTENT OF SLAG
 WITH REGARD TO PFA, REPLACEMENT LEVEL OF 25%–30%
OF CEMENT INCREASES SULFATE RESISTANCE OF
CONCRETE

56. STRENGTH & DURABILITY
FREEZE-THAW ACTION
 DETERIORATION OF CRITICALLY SATURATED CONCRETE DUE TO FREEZING OF
WATER
 TYPICAL SIGNS OF FREEZE–THAW DETERIORATION: SPALLING & SCALING, LARGE
CHUNKS OF CONCRETE (cm SIZE) BREAKING OFF, EXPOSED AGGREGATE & SURFACE
PARALLEL CRACKING
 AIR VOIDS WITHIN CONCRETE PROVIDE GOOD FROST RESISTANCE
 PORE SYSTEM IN SOME AGGREGATES SHOW SUSCEPTIBILITY TO DAMAGE FROM
FREEZE–THAW (.) HENCE EFFORTS ARE ALSO FOCUSED ON IDENTIFYING DAMAGE-
RESISTANT AGGREGATES
 CONCRETE WITH HIGH WATER CONTENT & HIGH W/C RATIO IS LESS FROST
RESISTANT THAN CONCRETE WITH LOWER WATER CONTENT
 FREEZE–THAW RESISTANCE OF CONCRETE CONTAINING 30%–50% PFA REPLACING
CEMENT, SHOWED EXCELLENT RESULTS
 D-CRACKING: CRACKING OF CONCRETE, MOSTLY IN PAVEMENTS, CAUSED BY
FREEZE–THAW DETERIORATION OF COARSE AGGREGATE WITHIN CONCRETE
 TO PREVENT D-CRACKING: SELECT DURABLE MATERIALS

57. STRENGTH & DURABILITY
FREEZE-THAW ACTION
TRANSVERSE D-CRACKING LONGITUDINAL D-CRACKING
7.33

58. DISCUSSION
 DISCUSSION MAY CONTINUE ON THE FOLLOWING
WHATSAPP GROUP:
 MODERN CONCRETE
 SEND: YOUR NAME, DESIGNATION, COMPANY
 TO Dr J D BAPAT MOBILE: 9422517402

59. THANKS !!

60. DISCUSSION
 DISCUSSION MAY CONTINUE ON THE FOLLOWING
WHATSAPP GROUP:
 MODERN CONCRETE
 SEND: YOUR NAME, DESIGNATION, COMPANY
 TO Dr J D BAPAT MOBILE: 9422517402

61. THANKS !!