TRANSFORMATION OF FLY ASH FROM THE STATE OF INDUSTRIAL WASTE TO THAT OF SOCIO-ECONOMIC WEALTH

1. TRANSFORMATION OF FLY ASH FROM THE STATE OF INDUSTRIAL WASTE TO THAT OF SOCIO-ECONOMIC WEALTH Dr. Anjan K Chatterjee Coal Ash Institute of India & CONMAT TECHNOLOGIES PRIVATE LIMITED ICUFA 2013 KOLKATA

2. Past Initiatives for Promoting Fly Ash • National Housing Policy (1988) : Exemption of excise duty for fly ash bricks • BMPTC (1990) : Fly ash bricks promotion with CPWD, DDA, DESU and NTPC. • HUDCO & NHB (1990) : Initiation of financing the fly ash based projects. • Department of Power (1990) : Setting up of a Working Group for drafting policy / guidelines. • Fly Ash Mission under Department of Science & Technology (1993) : Thrust on application promotion.

3. FLYASH UTILISATION BY CLASS OF APPLICATION

4. RISE OF FLY ASH IN APPLICATION HORIZONS IN SIX DECADES

5. FLY ASH GENERATION AND UTILISATION IN INDIA Source : FAUP

6. PAST AND FUTURE POTENTIAL OF FLY ASH UTILISATION (Mnt) Source : FAUP

7. BRIEF HISTORY OF FLY ASH USAGE AS SUPPLEMENTARY CEMENTITIOUS MATERIAL • First Anonymous report : An investigation of the pozzolanic nature of coal ashes (Engineering News, Vol.71, No.24, 1914, pp. 1334 – 35). • Pioneering research at the University of California, Berkeley (Davis R.E., Carlson R.W., Kelly J.W. and Davis H.E., Properties of Cements and concretes containing fly ash, Journal of the American Concrete Institute, Vol.33, 1937, pp 577 – 611). • Construction of Hungry Horse Dam in Montana : USBR Report CH – 95, 1948. • Proliferation of use in the next half century. • The first standard in India published in 1966.

8. American Road & Transportation Builders AssociationTransportation Development Foundation • Fly ash is a key component of high performance concrete pavement designed for a lifespan of 30 – 60 years for concrete roads compared to the current average of 20 – 25 years. • The cost to build roads, runways and bridges would increase by an estimated $104.6 billion over the next 20 years, if fly ash is no longer available as a transportation construction building material.

9. ARTBA FOUNDATION STUDYESTIMATE OF THE POTENTIAL BENEFITS IN ACORDANCE WITH THE DESIGNED SERVICE LIFE OF ROADS • $ 25 billion over 20 years if built to last 35 years • $ 33.5 billion over 20 years if built to last 40 years • $ 51.5 billion over 20 years if built to last 50 years • $ 65.4 billion over 20 years if built to last 60 years

10. RELATIVE ECONOMIC ADVANTAGE OF CONCRETE PAVEMENT WITH FLY ASH IN INDIA • An illustration for 1 km x 2 lane 7m wide pavement. • Soil CBR of 5. • A life span of 25 years (against 15 years for flexible pavement). • Maintenance every 5 years. NPV of Whole Life Cycle Costs (Rs. Lakhs)

11. FLY ASH IN CEMENT MAKING WITH THREE TO FIVE FOLD VALUE ADDITION

12. TREND OF PRODUCTION OF BLENDED CEMENTS IN INDIA IN THE LAST TWO DECADES

13. TRANSPORTATION OF FLY ASH FROM POWER PLANT TO CEMENT PLANT Fly Ash conveying pipe line Overall view Fly Ash conveying pipe rack

14. FLY ASH TRANSPORTATIONSOME ESSENTIAL FACILITIES Ash Intake Vessel Fly Ash Transport Compressor Fly Ash Control Room Fly Ash Silo Loading System

15. FLY ASH ATTRIBUTES AND GROUP CENTROIDS

16. PARTICLE MORPHOLOGY OF THE INDIAN FLY ASHES (Magnification 200 X) (a) Angular glass fragments (b) Acicular mullites in a spherical glassy particle (c) Darker glassy spherical particles

17. COMPOSITIONAL VARIABILITY AT THE PARTICULATE LEVEL Fly Ash 1 Canadian Fly Ash for reference

18. SPECIFIC SURFACE AREAINDIAN FLY ASHES SOURCE NO

19. COMPARATIVE CRYSTALLINITY OF THE INDIAN AND FOREIGN FLY ASH SAMPLES Indian Fly Ash 2 Indian Fly Ash 1 Canadian Fly Ash

20. PSEUDO – TERNARY COMPOSITIONAL DIAGRAM FOR ALKALI ACTIVATION OF FLY ASHES • • Typical Indian fly ashes

21. LIME REACTIVITY - INDIAN FLY ASHES

22. IMPEDIMENTS IN ENHANCING THE APPLICATION POTENTIAL OF INDIAN FLY ASHES • Inter-Source and Intra-Source variability • Wide distribution of particle size • High order of crystallinity • Wide fluctuation of surface area

23. CURRENT TECHNOLOGY FOR QUALITY UPGRADATION OF INDIAN FLY ASHES FOR HIGHER REACTIVITY

24. ULTRAFINE GRINDING OF FLY ASH TO MAKE LARGE CHANGE OF PROPERTIES • Mechano - chemical activation – chemical conversions in fly ash particles by milling. • Possibilities of introducing elastic, plastic and shear deformations leading to fracture and amorphization. • Options : • Ball milling • Use of high energy vibratory mills • Application of tower mills

25. TYPICAL ULTRAFINE BALL MILLING OF THE INDIAN FLY ASH Interesting to note that the high-Blaine fly ash demonstrated d50 of 5 – 7 μm, while the metals and Intermetallics in a ball mill can be ground to 200-5 nm in 4 – 12 h.

26. COMPARATIVE PARTICLE SIZE CHARACTERISTICS OBTAINED FROM CLASSIFICATION & FINE GRINDING Ground and classified Fine Fly Ash Raw D50 : 19.2 μm Ground D50 : 8.4μm Cycloned D50 : 2.0 μm

27. THE MOST SIGNIFICANT TREND OF DEVELOPMENT OPC Blended (PPC / PSC / PLC) Multi component Portland Composite cement Nano – Particulate Cement

28. NANO CEMENT TECHNOLOGY Simoloyer Milling Device

29. HIGH ENERGY VIBRATORY MILLS FOR INDIAN FLY ASHES • A lab mill has shown the potential of increasing the Blaine surface of fly ash from 260 to 950 m2/kg in 1 hour. • The d50 value, however, remained 6-7 μm reduced from 30 μm. • The product behaviour resembles that of a ball mill. • A pilot mill of 1.5 tph rated throughput with twin tubes of 600 x 3500 mm length has been installed in an Indian Cement plant. • The scaling-up problems of low reduction ratio (<2.0) and high specific power consumption are noticed in preliminary operations. Vibratory Mill

30. UNSUITABILITY OF TOWER MILLS FOR FLY ASH GRINDING • The Indian attempts of trial runs with fly ash in Tower mills have not been very encouraging. • 2. Although throughputs of upto 100 tph are claimed for Tower mills or its improved version of vertimills with product fineness of 1-100 μm, for Indian fly ashes achieving a d50 of 10 μm became difficult with very high specific power consumption. Use of coarse media (6 mm) and low tip velocity of the stirrer (3 m/s) perhaps were responsible. Tower Mill

31. PARTICLE SIZE AND CRYSTALLINITY EFFECTS OF SILICO – ALUMINATE MATERIALS RESEMBLING FLY ASHES ON THEIR PERFORMANCE

32. PERFORMANCE COMPARISON OF CLASSIFIED FINE FLY ASH WITH SILICA FUME IN CONCRETE Composition/PropertiesControl F A S F d50, μm -- 3 <0.1 Addition, % 0 10.0 10.0 W/C 0.40 0.40 0.40 Cement, Kg/m3 400 357 356 Slump, mm 100 80 80 Compressive Strength, MPa 7 day 56.2 54.5 71.0 28 day 67.9 68.7 80.7 Rapid Cl- permeability, coulomb 7 day 2922 1083 429 28 day 2340 758 297

33. RELATIVE PERFORMANCE OF SILICA FUME AND SILICA COLLOID IN POZZOLANIC REACTION CH quantity based on XRD counts per second Weight loss between 4000C to 5000C with respect to time [C : Reference; SF 4 : 4% addition; SF 8 : 8% addition; SF 16 : 16% addition; KF : 4% Silica colloid; KF 8 : 8% Silica colloid addition]

34. XRD PATTERNS OF DIFFERENTLY MILLED FLY ASHES AND SILICA GEL 2 – Theta - Scale XRD pattern of silica gel 2 – Theta - Scale XRD pattern of differently milled fly ash

35. DETERMINATION OF CALCIUM HYDROXIDE IN DIFFERENT PPC BLENDS ON 3-DAY HYDRATION IN PASTE BY TG – DSC AT 10000C

37. STATUS OF PRESENT-DAY COMMINUTION AND CLASSIFICATION OF CRYSTALLINE FLY ASHES AND THEIR PERFORMANCE • Mean particle size generally achieved 8-10 µm and with special efforts and facilities 2-4 µm. • Performance of pozzolanicity and reactivity commensurate with increased surface created for denser packing and higher nucleation. • Performance of these fly ashes still far away from that of silica fume, silica colloid or silica gel. • New opportunities for high-tech applications.

38. FLY ASH UTILISATION CLASSIFICATION FOR HIGH VALUE ADDED APPLICATIONS

39. BIOTREATMENT POTENTIAL OF FLY ASH • ADHESION OF MICROORGANISMS TO MINERAL SURFACE • BIOCATALYSED OXIDATION/ REDUCTION • ADSORPTION / CHEMICAL INTERACTION OF METABILIC PRODUCTS

40. SOME MICROORGANISMS IMPLICATED IN METAL ACCUMULATION

41. TREATMENT SCHEME

42. NEWER OPPORTUNITIES WITH FLY ASH • RECOVERY / REMOVAL OF TRACE ELEMENTS (BIOLOGICAL AND/OR HYDROMETALLURGICAL METHODS) 2. PHOSPHATIC COMPOUNDS OF ALUMINIUM (AND SILICA ?) 3. SYNTHESIS AND SEPARATION OF MULLITE

43. CONCLUDING REMARKS • The scope of enhancing the potential use of Indian Fly Ashes is phenomenally large and is expected to be magnified further in decades to come. • The chemico-physical properties of the Indian fly ashes create impediments in improving their reactivity, which is essential to achieve enhanced usage of this resource. • To a large extent the adoption of efficient cyclone-based classification technology has helped the industry to separate the fine particles below 10 µm size with improved interaction properties in cement and concrete.

44. CONCLUDING REMARKS (Cont’d) • The industrially practised ultrafine grinding technology has not shown any viable process so far to reduce the mean particle size of Indian fly ashes to submicrocrystalline level. • No clear indications of real mechano-chemical activation of the fly ashes are visible in micron-sized grains. • Perhaps the feasibility of particle size reduction to 300 – 100 nm needs to be explored for significantly large changes in grain properties. • While the cyclone classification coupled with micron-size fine grinding may satisfy the immediate technology needs of the industry, some of the emerging ultrafine grinding technologies should receive careful attention.

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