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Incorporating Physical and Chemical Characteristics of Fly Ash in Statistical Modeling of Binder Properties. Presented at Second International Conference on Sustainable Construction Materials and Technologies, Ancona , Italy Prasanth Tanikella and Jan Olek Purdue University.

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  1. Incorporating Physical and Chemical Characteristics of Fly Ash in Statistical Modeling of Binder Properties Presented at Second International Conference on Sustainable Construction Materials and Technologies, Ancona, Italy PrasanthTanikella and Jan Olek Purdue University June 30th, 2010 PrasanthTanikella and Jan Olek - Purdue University

  2. Objectives and Hypothesis • The goal of this research was to: • Characterize two groups of fly ashes (Class C and Class F) • Statistically verify the importance of their physical and chemical properties on the performance of binary paste systems • Scope of the Project (2 Phases) • Phase 1 – Characterization of Fly Ashes • Phase 2 – Effect of Fly Ashes on the Properties of Binary Paste Systems (cement + fly ash) PrasanthTanikella and Jan Olek - Purdue University

  3. Phase 1 – Characterization of Fly Ashes • Collected 20 different fly ashes (13 Class C and 7 Class F) • A database summarizing the physical and chemical characteristics of the collected fly ashes and the impact of these properties on the behavior of binders would benefit the engineers, contractors and concrete producers Test Methods PrasanthTanikella and Jan Olek - Purdue University

  4. Phase 1 ResultsRange of chemical compositions PrasanthTanikella and Jan Olek - Purdue University

  5. Phase 1 ResultsRange of physical characteristics PrasanthTanikella and Jan Olek - Purdue University

  6. Phase 1 ResultsXRD – Typical Class F Fly Ashes XRD pattern for Elmer Smith fly ash (Type I) (Type I) • 1. Quartz – SiO2 2.Mullite – Al6Si2O13 3. Anhydrite – CaSO4 4. Hematite – Fe2O3 5. Magnetite – Fe3O4 6. Lime – CaO • Measured magnetic content is generally very high (with two exceptions – Type II) • A hump, representing a silica-type glass with a maximum at 2θ=~25° is visible • Glass “hump” is generally higher than that observed for Class C ashes Counts ~ 250 2θ XRD pattern for Miami 7 fly ash (Type II) Counts ~ 250 2θ PrasanthTanikella and Jan Olek - Purdue University

  7. Phase 1 ResultsXRD - Typical Class C Fly Ash • Includes 1. Quartz – SiO2 2. Anhydrite – CaSO4 3. Merwinite – Ca3Mg(SiO4)2 4. Periclase – MgO 5. Lime – CaO • Glass peak is similar for all the ashes of this type • Magnetite might be present in the fly ash, either in crystalline form or in the glass • A hump, representing a calcium-aluminate type of glass with a maximum at 2θ=~30° is visible Counts ~ 300 2θ XRD pattern for Hennepin fly ash PrasanthTanikella and Jan Olek - Purdue University

  8. Phase 1 ResultsXRD – Glass Content Estimation • Glass content was empirically estimated by calculating the area under the glass hump • Three softwares were used • xyExtract– To extract points from the XRD pattern • LabFit– To fit the curve very precisely through the extracted points • Sicyon Calculator– To integrate the fitted curve PrasanthTanikella and Jan Olek - Purdue University

  9. Phase 1 ResultsParticle Size Distributions • Class F and Class C ashes form two different bands of PSDs • The band of Class C ashes is shifted towards the left of the band of Class F ashes Class C Class C Class F PrasanthTanikella and Jan Olek - Purdue University

  10. Phase 1 ResultsDiscrepancies in PSD • Discrepancies observed in PSD • The pipette analysis seems to work well for particles larger than 5 micron • The results below 5 microns seem to diverge from either of the curves • From the data it is reasonable to assume that the PSD based on Lab 1 (Purdue) data is accurate 5 5 PrasanthTanikella and Jan Olek - Purdue University

  11. Phase 1 ResultsMorphology of Class F ashes • Large variation in the sizes and shapes of the particles • Particles with rugged surface are generally magnetic, contrary to the Class C fly ashes • Type II ashes have relatively smaller number of unburnt carbon particles than Type I ashes, but bigger particles have been observed 10 μm Zimmer 5 μm Elmer Smith 10 μm Petersburg 3 μm Mill Creek PrasanthTanikella and Jan Olek - Purdue University

  12. Phase 1 ResultsMorphology of Class C ashes • Wide range of sizes of spherical particles • Many hollow particles with shell generally composed of silica and alumina • Frequent irregularly-shaped particles (often with rugged surfaces) predominantly composed of sulfates or magnesium, or rarely sodium 10 μm Labadie 5 μm Kenosha 3 μm Will County 10 μm Rush Island PrasanthTanikella and Jan Olek - Purdue University

  13. Summary –Phase 1Characterization of fly ashes • Significant variations in the chemical and physical characteristics of fly ashes observed • The strength activity index of Class C ashes was higher than Class F ashes • The glass content for all the Class C ashes was higher than the glass content for all but two Class F ashes, thus indicating that although Class C fly ashes have less glass than these two Class F ashes, the glass in Class C ashes is more reactive • The morphology of the ashes was similar irrespective of the class, with a few exceptions PrasanthTanikella and Jan Olek - Purdue University

  14. Summary – Phase 1Characterization of fly ashes • The particle size distributions of class C and class F ashes were significantly different • All mean particle sizes in class F were larger than mean particle sizes in class C ashes, resulting in a lower surface area of class F ashes • The LOI values of all class F ashes were higher than that of the C ashes PrasanthTanikella and Jan Olek - Purdue University

  15. Phase 2 - Evaluation of the hydration characteristics of cement-fly ash binder systems • Binder systems consisted of portland cement with 20% (by weight) replaced by fly ash • Pastes with constant water/binder ratio (0.41) were tested for various properties including, • Initial Time of Set – Vicat needle (ASTM C 191) • Heat of Hydration – Isothermal Calorimetry (at a constant temperature of 21 oC) • Amount of Ca(OH)2 at ages 1, 3, 7 and 28 days - TGA • Non-evaporable water content at 1,3 7 and 28 days – TGA • Rate of strength gain at 1, 3, 7 and 28 days – Strength activity index (ASTM C 311) PrasanthTanikella and Jan Olek - Purdue University

  16. Phase 2 Initial Setting Time - Results Flash Set • Range of set time for Class C ashes – (1 to 4.5 hours) • Range of set time for Class F ashes – (2.5 to 3.5 hours) PrasanthTanikella and Jan Olek - Purdue University

  17. Phase 2 A Typical Calorimetry Curve Time of Peak Heat Heat of Hydration (W/kg) • Data acquired from the calorimeter curve • Peak heat of hydration (W/kg) • Time of peak heat of hydration (minutes) • Total heat of hydration (J/kg) – (Area under the curve from 60 minutes to 3 days) Peak Heat of Hydration Time (minutes) Total Heat PrasanthTanikella and Jan Olek - Purdue University

  18. Phase 2 Peak Heat of Hydration - Results Class C Class F • Most ashes tend to reduce the peak heat of hydration compared to cement • Class F ashes in general have a higher peak heat of hydration than Class C ashes • Kenosha, the fly ash with the lowest peak heat of hydration had a flash set PrasanthTanikella and Jan Olek - Purdue University

  19. Phase 2 Time of Peak Heat of Hydration - Results Class C Class F • Most ashes tend to delay the occurrence peak heat of hydration compared to cement • Class C ashes in general have a higher time of peak heat than Class C ashes • Kenosha, the fly ash with the lowest peak heat of hydration had longest time of peak heat PrasanthTanikella and Jan Olek - Purdue University

  20. Phase 2 Thermo-gravimetric Analysis (TGA) • Calcium hydroxide content and non-evaporable water content were estimated using TGA at various ages (1, 3, 7 and 28 days) • Calcium Hydroxide content between 480oC and 550oC (carbonation taken in to account) • Non-evaporable water content calculated according to Barneyback, 1983. PrasanthTanikella and Jan Olek - Purdue University

  21. Phase 2 Calcium Hydroxide Content at 1 day - Results • Most ashes tend to reduce the amount of calcium hydroxide at 1 day compared to plain cement paste (with some exception) • Class F ashes have a slightly higher CH content than Class C ashes at early ages PrasanthTanikella and Jan Olek - Purdue University

  22. Phase 2 Calcium Hydroxide Content at 28 days - Results • Most of the ashes show a higher amount of calcium hydroxide at 28 day compared to plain cement paste • Difference in the rates of reactions in the fly ashes PrasanthTanikella and Jan Olek - Purdue University

  23. Phase 2 Strength Activity Index at 28 days - Results Class C Class F • All of the Class C ashes show a higher strength at 28 days compared to plain cement paste while Class F ashes show a lower strength comparatively PrasanthTanikella and Jan Olek - Purdue University

  24. Phase 2 Statistical Modeling of Binary Binders PrasanthTanikella and Jan Olek - Purdue University

  25. Phase 2 Statistical Modeling of Binary Binders PrasanthTanikella and Jan Olek - Purdue University

  26. Phase 2 Dependent Variables • Initial time of set • Peak heat of hydration • Time of peak heat of hydration • Strength activity index at 28 days • Calcium hydroxide at 28 days PrasanthTanikella and Jan Olek - Purdue University

  27. Phase 2 Ten Models with the highest Adj-R2 – Set Time PrasanthTanikella and Jan Olek - Purdue University

  28. Phase 2 ANOVA Table (Class C Ashes) – (SAI) at 28 days PrasanthTanikella and Jan Olek - Purdue University

  29. Phase 2 ANOVA Table (Class C Ashes) – (SAI) at 28 days PrasanthTanikella and Jan Olek - Purdue University

  30. Summary-Phase 2Binary Binder Systems • Physical characteristics of fly ash had a higher effect than chemical characteristics of fly ash • Surface area was found to be the most influencing variable affecting most of the properties of the binder system at both early and later ages • Variables including SAI (at later ages) and time of peak heat of hydration can be predicted accurately using the respective statistical models PrasanthTanikella and Jan Olek - Purdue University

  31. Conclusions • Class C and F ashes were significantly different in both their physical characteristics and chemical composition • There was significant difference in the effect of the two classes on binder properties • The performance of the two types (I and II) of Class F ashes was similar when incorporated in the binder systems • Both physical and chemical characteristics of fly ash had an effect on the binder systems PrasanthTanikella and Jan Olek - Purdue University

  32. Conclusions • The sets of variables affecting each of the properties were unique • The signs of the coefficients in the models indeed pointed out the type of effect on the property • The statistical analysis of the properties of binary binders allowed us to draw inferences about the characteristics of fly ash which held the highest importance PrasanthTanikella and Jan Olek - Purdue University

  33. Conclusions • Some of the properties could not be accurately predicted by the statistical models with good significant as there were errors introduced by the limited number of variables chosen for modeling • Specific surface area of the fly ash had the highest impact on all the properties of binder systems PrasanthTanikella and Jan Olek - Purdue University

  34. THANK YOU PrasanthTanikella and Jan Olek - Purdue University

  35. Phase 2 ANOVA Table (Class C Ashes) – Set Time PrasanthTanikella and Jan Olek - Purdue University

  36. Phase 2 Observed Vs Predicted (Class C Ashes) – Set Time PrasanthTanikella and Jan Olek - Purdue University

  37. Phase 2 ANOVA Table (Class F Ashes) – (SAI) at 28 days PrasanthTanikella and Jan Olek - Purdue University

  38. Phase 2 ANOVA Table (Class F Ashes) – (SAI) at 28 days PrasanthTanikella and Jan Olek - Purdue University

  39. Phase 2 ANOVA Table (Class F Ashes) – Set Time PrasanthTanikella and Jan Olek - Purdue University

  40. Phase 2 Observed Vs Predicted (Class F Ashes) – Set Time PrasanthTanikella and Jan Olek - Purdue University

  41. Phase 2 Summary of Statistical Analyses for all Dependent Variables PrasanthTanikella and Jan Olek - Purdue University

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