spr 3020 updating physical and chemical characteristics data of fly ash in concrete prasanth...

SPR 3020Updating Physical and Chemical Characteristics Data of Fly Ash in

Concrete

Prasanth Tanikella and Jan OlekPurdue University, School of Civil Engineering,

West Lafayette, Indiana

1

Presented to the SAC CommitteeOctober 3rd , 2008

Presentation Outline

Research Objective Scope of the original project Proposed expansion of the scope Status of the project – Review of the tasksOriginal Project Literature Review Characterization of available fly ashes - Methods of examination - Results and analysis - ConclusionsProposed Expansion Evaluation of the hydration characteristics of binders Binary binder systems Ternary binder systems Summary and conclusions of the study

Prasanth Tanikella - Purdue University 2

Research Objective

• To revise and update the information on the basic physical and chemical characteristics of fly ashes available to INDOT and to the industry in Indiana


Scope of the Original Project

The general scope of the project includes collecting a suite of fly ashes available for use in concrete in Indiana and characterizing them for the following properties

Chemical Properties• Total chemical composition (silicon, calcium, magnesium, titanium,

aluminum, iron, sodium, potassium, phosphorus and sulfur)• Loss-on Ignition, carbon content• Soluble sulfates and alkalis• Content of magnetic particlesPhysical Properties• Particle size distribution• Specific surface• Specific gravity• Mineral composition using X-Ray Diffraction• Morphology of particles using SEM and optical microscopy• Pozzolanic activity index with cement

Prasanth Tanikella - Purdue University6

Proposed Expansion of the ScopeNeed for the Proposed Expansion of the Scope• Fly ash is a very complex material, with a highly variable chemical and physical

characteristics• Recent changes in coal combustion technologies and environmental regulations

resulting in more variable quality and less predictable availability• Combined with the inherent chemical and physical variations, these additional changes

require more comprehensive tools for quality control and performance prediction• Hence, there is a need to estimate the properties of cement+ fly ash binder systems as

a function of the physical and chemical characteristics of the components to aid with decisions regarding the selection of fly ashes of variable quality

Proposed Expansion• To estimate (quantitatively) the glass content in the fly ashes and its chemical

composition as glass is the most reactive component in fly ash• To investigate the role of the fundamental characteristics of fly ash in binder hydration• To quantify the synergistic effects of adding two fly ashes to cement and to develop

methods for selection of the type and the amount of fly ashes to be added to achieve the desired hydrated binder characteristics

• Statistically model the effect of characteristics of fly ash on the hydration process of binary and ternary binders as the function of fly ash composition and glass characteristics


Task Review and Status

Phase I - Original TasksTask 1: Literature Review CompletedTask 2: Collection of Fly Ash Specimens CompletedTask 3: Laboratory Testing CompletedTask 4: Data Analysis CompletedTask 5: Development of fly ash database In ProgressTask 6: Development of a report Completed

Phase II - Newly Added TasksTask 1N: Literature review of the hydration characteristics Completed

of binary and ternary binder systemsTask 2N: Selection of the experimental techniques CompletedTask 3N: Laboratory Experimentation

- Heat of Hydration (Isothermal Calorimetry) In Progress - Setting time Completed - Porosity at different ages (Mercury Intrusion Porosimetry) In Progress - Rate of strength development In Progress


Task Review and Status

Task 3N: Laboratory Experimentation… Continued - Estimation of unhydrated fly ash (Selective To be Performed dissolution and TGA) - Estimation of the lime content (TGA) To be Performed - Estimation of the glass content in fly ash To be Performed - Estimation of the non-evaporable water content To be Performed - Qualitative X-ray diffraction at different ages In Progress

of hydration of bindersTask 4N: Statistical analysis and modeling of the data In ProgressTask 5N: Development of an electronic program for the To be Performed

estimation of the amount and type of fly ash(s) to be added to cement based on the chemical and physical characteristics of fly ash to achieve the desired properties of the binder

Task 6N: Report writing and editing To be Performed



Phase I - Original Project Task 1 - Literature Review Task 2 - Collection of Specimen Task 3 - Characterization of available fly ashes - Methods of examination - Results Task 4 - Data analysis and conclusions Tasks 5 & 6 - Report Writing and Database developmentPhase II - Proposed Expansion Evaluation of the hydration characteristics of binders Binary binder systems Ternary binder systems Summary and conclusions of the study


Task 1 – Literature Review

• A thorough literature survey was performed on the ranges of physical characteristics and chemical compositions of the fly ashes and available testing methods

• Large variations in chemical compositions and physical characteristics of fly ashes universally reported

• Larger volume of data available on low calcium fly ashes (Class F)

• Current trends indicate increased availability of Class C fly ashes and decline in the availability of Class F fly ashes

• Current INDOT’s list of approved fly ashes contains 13 class C ashes and 7 class F ashes

• A good correlation for the physical and chemical characteristics of fly ash with the hydration properties has been reported



Phase I - Original Project Task 1 - Literature Review Task 2 - Collection of Specimen Task 3 - Characterization of available fly ashes - Methods of examination - Results Task 4 - Data analysis and conclusions Tasks 5 & 6 - Report Writing and Database developmentPhase II - Proposed Expansion Evaluation of the hydration characteristics of binders Binary binder systems Ternary binder systems Summary and conclusions of the study


Task 2- Collection of fly ash specimens

• Collected 20 different fly ashes (13 Class C and 7 Class F)

• 15 of them ( 9 class C ashes and 6 class F ashes) are currently on the INDOT list of approved pozzolanic materials

• A database summarizing the physical and chemical characteristics of the collected fly ashes would benefit the engineers, contractors and concrete producers in choosing the fly ashes. Such database is currently in preparation



Phase I - Original Project Task 1 - Literature Review Task 2 - Collection of Specimen Task 3 - Characterization of available fly ashes - Methods of examination - Results Task 4 - Data analysis and conclusions Tasks 5 & 6 - Report writing and Database developmentPhase II - Proposed Expansion of the Scope Evaluation of the hydration characteristics of binders Binary binder systems Ternary binder systems Summary and conclusions of the study


Task 3 - Methods of Examination

Total chemical analysis and loss-on ignition according to ASTM C 311

Soluble sulfates and soluble alkalis using ion chromatography and atomic absorption spectroscopy

Particle size distribution using laser particle size analyzer at the laboratory of Boral Material Technology Inc, Purdue’s particle size analyzer and sedimentation method

Content of magnetic particles using a teflon coated bar magnet

Crystalline components using qualitative X-ray diffraction Morphologies of particles using scanning electron

microscopy Strength activity index with portland cement according to

ASTM C 311


ResultsChemical composition of fly ashes PROPERTY

CaO(%) SiO2(%) Al2O3(%) Fe2O3(%) Sulfate (%)

Alkali Content as Na2O (%)

LOI(%)

FLY ASH Class

Petersburg F* 1.86 43.82 21.74 25.29 0.87 2.29 1.39

Elmer smith F* 9.31 41.6 17.74 22.02 0.60 2.32 2.37

Trimble F 2.5 46.91 21.08 19.9 1.09 2.45 1.89

Miami 8 F* 3.98 55.52 26.02 4.62 0.76 2.55 2.43

Mill creek F* 5.42 47.48 19.99 18.52 0.69 2.55 1.38

Zimmer F* 4.94 38.66 18.96 24.9 2.08 1.44 1.48

Miami 7 F* 1.25 55.89 29.45 4.96 0.42 2.20 2.31

Rockport C 16.98 43.65 21.76 6.58 0.45 2.08 0.9

Joppa C* 26.23 35.75 18.01 6.36 0.07 2.31 0.35

Kenosha C 23.35 37.78 20.11 5.87 0.53 2.18 0.38

Miller C* 24.62 36.38 18.74 6.03 0.52 2.08 0.44

Hennepin C* 21.8 40.36 19.38 5.91 0.35 1.99 0.61

Joliet C* 26.98 32.12 17.88 6.41 1.28 3.92 0.49

Vermilion C* 23.92 39.13 18.77 6.19 0.22 1.91 0.43

Will county C* 26.97 32.3 18.55 6.47 0.43 3.06 0.35

Rush island C 27.66 34.23 16.91 6.86 0.05 2.26 0.17

Baldwin C* 25.23 35.06 19.39 6.25 0.28 2.24 0.49

Labadie C 24.26 37.03 19.28 6.46 1.14 1.94 0.25

Schafer C* 20.29 41.9 19.32 6.76 0.48 1.83 0.44

Edwards C* 24.28 33.15 19.21 10.11 0.75 1.63 0.43* INDOT list of approved fly ashes

ResultsPhysical characteristics of fly ashes

PROPERTY

Blaine’s Specific surface (cm2/g)

Mean Size (microns)

Specific Surface - LPSD(cm2/g)

Pozzolanic activity index (%)

Magnetic particles (%) Specific Gravity FLY ASH Class

Petersburg F* 2391 28.37 9849 104.3 37.72 2.63 (2.55)

Elmer smith F* 3092 33.24 6344 109.9 32.99 2.64 (2.52)

Trimble F 3253 27.35 8857 109.1 26.39 2.69

Miami 8 F* 3600 31.58 13012 112.3 4.18 2.22 (2.21)

Mill creek F* 3739 26.35 10295 125.7 24.9 2.60 (2.46)

Zimmer F* 3782 26.1 11308 96.2 35.32 2.68 (2.64)

Miami 7 F* 4088 30.41 12592 118.2 3.68 2.26 (2.22)

Rockport C 4354 32.2 11963 134.1 3.5 2.56

Joppa C* 4371 18.37 17597 135.9 0.31 2.72 (2.70)

Kenosha C 4452 17.35 16577 121.2 0 2.80

Miller C* 4851 24.93 17089 123 0 2.63 (2.66)

Hennepin C* 5125 16.88 16457 136.5 0.07 2.70 (2.35)

Joliet C* 5356 14.48 19776 116.7 0 2.84 (2.46)

Vermilion C* 5536 13.85 17928 136.7 0.12 2.69 (2.64)

Will county C* 5907 14.85 19646 140.2 0 2.84 (2.49)

Rush island C 5924 20.77 17477 127.7 0 2.81

Baldwin C* 6102 21.99 15492 127.2 0 2.72 (2.66)

Labadie C 6269 16.69 16503 118.6 2.89 2.75

Schafer C* 6428 18.87 14679 118.8 2.7 2.58 (2.59)

Edwards C* 7306 15.08 22075 133 3.34 2.63 (2.65)19* INDOT list of approved fly ashes. SG listed in () indicate vales from INDOT’s list of approved fly ashes.

ResultsParticle Size Distributions

• The particle size distributions (PSDs) for 3 typical class C fly ashes and 3 typical class F fly ashes are shown here

• 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

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ZimmerMiami 7TrimbleBladwinJolietHennepin

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ResultsXRD – Typical Class F (Type I) Fly Ash

Tyical X-ray pattern for a class F fly ash (Type I) – (5 out of 7 ashes)

Includes1. Quartz – SiO2

2. Anhydrite – CaSO4

3. Mullite – Al6Si2O13

4. Hematite – Fe2O3

5. Magnetite – Fe3O4

6. Lime – CaO• Measured magnetic content is

generally very high• 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 Prasanth Tanikella - Purdue University 21

XRD pattern for Elmer Smith fly ash

ResultsXRD – Typical Class F (Type II) fly ash

X-ray pattern for a class F fly ash (Type II) – 2 out of 7 ashes (both from Miami)

Includes1. Quartz – SiO2 2. Mullite – Al6Si2O13

• The measured content of magnetic paricles was 3.68%

• However, no crystalline iron oxide peaks were detected

• A hump, representing a silica type of glass with a maximum at 2θ=~24° is visible (slightly lower than class F (Type I) glass


XRD pattern for Miami 7 fly ash

ResultsXRD - Typical Class C Fly Ash

X-ray pattern for a typical class C fly ash

Includes1. Quartz – SiO2

2. Anhydrite – CaSO4

3. Merwinite – Ca3Mg(SiO4)2

4. Periclase – MgO5. 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=~32° is visible


XRD pattern for Hennepin fly ash

ResultsMorphology of class F (Type I) ashes

There is a large variation in the sizes and shapes of the particles

Particles with rugged surface are generally magnetic, contrary to the class C fly ashes

Many hollow particles present

Relatively smaller number of unburnt carbon particles, but bigger particles have been observed, which is consistent with the higher LOIs values observed in Class F ashes

Prasanth Tanikella - Purdue University 24Mill CreekPetersburg

Elmer SmithZimmer

ResultsMorphology of class F (Type II) ashes

Miami 7, a class F fly ash was found to have numerous irregular particles

The broken curved fragments contain silica and alumina

It could have been a hollow particle before it broke

Miami 8 - similar chemical composition to Miami 7 fly ash

Contains more spherical particles compared to Miami 7 ash


Miami 7 Fly ash

Miami 8 Fly ash

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


Rush Island

KenoshaLabadie

Will County


Phase I - Original Project Task 1 - Literature Review Task 2 - Collection of Specimen Task 3 - Characterization of available fly ashes - Methods of examination - Results Task 4 - Data analysis and conclusions Tasks 5 & 6 - Report writing and Database developmentPhase II - Proposed Expansion Evaluation of the hydration characteristics of binders Binary binder systems Ternary binder systems Summary and conclusions of the study


Task 4 – Data AnalysisChemical analysis of fly ashes

The number of available Class C fly ashes is much higher than the number of the available Class F fly ashes

With respect to chemical composition two classes of fly ashes are consistent in their own class, with a few exceptions (as indicated below)

Class F ashes Class F ashes can be divided into two Types (I and II) as they are different

in most respects including chemical composition and physical characteristics

Both Type II ashes are products of the same coal plant (Miami) For both types, the combined silicon, aluminum and iron content varies

from 81% to 91% Iron oxide content varies from 18% to 25%, except for two fly ashes

(Miami 7 and Miami 8) which have much lower iron content (close to 5%) Typical CaO contents below 5% (except for Elmer Smith) Moderate alkali contents of around 2.3% for most Sulfate contents of fly ashes less than 3.1% LOI (more than 1%) is much higher compared to class C ashes



Class C Ashes Typical combined silicon, aluminum and

iron content of 56% to 65% (except Rockport =72%) which has a high SiO2

content (43%) Iron oxide content does not vary a lot

from 6%, except for one fly ash (Edwards=10%)

Typical CaO contents of 22% to 26% (except Rockport = 17%)

Moderate alkali contents of around 2% for most, with almost none of the alkalis soluble

Sulfate contents less than 1.3% Loss on Ignition (LOI) less than 1%

Chemical analysis of fly ashes

• The particle size distribution is consistent within each of the Class C ash and Class F ash groups. However, discrepancies have been observed in PSD obtained form laser particle size analyzer (LPSA) performed at two different laboratories (will be addressed later)

• The percentage of particles less than 1 micron in size is found to be less than 1%, consistent with the literature

• Large difference between the mean sizes of the two classes of ashes, with the particle size of class F fly ash being higher

• The average pozzolanic activity index of class C ashes (128.5%) is higher than class F ashes (110%). This can be explained by the lower mean particle size and the presence of silica and lime in the glass phase

• The average strength activity index of class F (Type II) ash (115.25%) is higher than class F (Type I) ashes ( 109%)


Task 4 – Data AnalysisPhysical Characteristics of fly ashes

• The results of the pozzolanic activity index (PAI) indicate that the “Zimmer” fly ash (with PAI =96) does not meet the requirements of ASTM C 618 (PAI=100) and is thus not recommended for use in concrete

• The median density of class C ashes (around 2.72) is higher than the median density of class F, Type I ashes (around 2.64). Class F (Type II) ashes have the lowest density (around 2.23)

• The values of specific surface area of all class F ashes were lower than that of class C ashes, which is consistent with the higher mean particle sizes of class F ashes

• Also, the magnetic particle content in all the class F ashes (Type I) is much higher compared to all of those in class F (Type II) and class C ashes

• The magnetic particle content of class F (Type II) ashes was found to be the least of all the ashes


Task 4 - Physical Characteristics of fly ashes

Task 4 - AnalysisDiscrepancies in PSD Data

Particle size distribution (PSD)

PSD analyzed in two laboratories using laser particle size analyzer (LPSA)

Significant differences were observed in the PSD obtained for most of the fly ashes, while a few agree up till a specific particle size


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Task 4 - AnalysisAndreasen Pipette Analysis

An attempt was made to resolve the differences in the observed PSD using the Andreasen Pipette

Particles suspended in dispersing solution

Particles settle at different rates. The rates depend on the radius and density of the particles

Stokes law used to calculate the particle size


Task 4 - AnalysisDiscrepancies resolved

The pipette analysis seems to work well for particles larger than 5 micron particle size and is coincident with Lab 1’s results. The results below 5 microns seem to diverge from either of the curves

Even though the sedimentation technique does not work well for particles smaller than 5 microns, based on the literature data it is reasonable to assume that the PSD based on Lab 1 data is accurate


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Task 4 - AnalysisX-ray Diffraction

In general, the fly ashes have been consistent in their own groups Class F ashes can be divided into two groups based on the chemical

composition found using X-ray diffraction Class F (Type I) ashes had relatively lower and narrower glass humps

compared to the Class F (Type II) ashes The glass humps of Class C fly ashes were smaller and narrower than

those for Class F (Type II) ashes but taller and narrower than those for Class F (Type I) ashes

The percentages of magnetic particles in Class F(Type I) ashes were very high (over 25%) and the strength activity indexes of these ashes were the lowest

The amounts of magnetic particles in Class F(Type II) ashes were the lowest (about 4%) but the PAIs of these ashes were higher than those of Class F (Type I) and much lower than those of Class C ashes

There content of magnetic particles in Class C ashes was negligible, which is also evident from the XRD analysis as no hematite and magnetite was found in most of these ashes


Task 4 - AnalysisMorphology

General Inferences

Very few particles above 200 microns in size

Quite a few large particle of almost 100 micron size

Also seen, large number of particles smaller than 5 microns

Most particles spherical A few pieces of carbon 20-25

micron in size can be seen with a “Swiss Cheese” structure

Fly ash particles are found inside some of the hollow particles


Task 4 - AnalysisMorphology

General Inferences

Conglomerates of large and very small particles of fly ash is visible

An irregular piece of fly ash is seen

Extremely large fragments of carbon particles are also seen

Very few rod like particles are found


Conclusions – Phase ICharacterization of fly ashes

• Significant variations in the chemical and physical characteristics of fly ashes observed

• Class C fly ashes more abundant than class F ashes • Class F ashes can be divided into two (Type I and Type II as defined) based on

the crystalline chemical composition seen using X-ray diffraction techniques• The reactivity (pozzolanic activity index) of class F Type I ashes was found to be

lower than class F Type II ashes• The reactivity of class C ashes was found to be the highest of the three classes• However, the glass hump of class C ashes was found to be lower than class F

Type II ashes, thus indicating that although Class C fly ashes have less glass, this glass is more reactive

• The morphology of the ashes was similar irrespective of the class, with a few exceptions

• 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 larger particle size also could lead to a lower reactivity in these ashes• The LOI values of all class F ashes were higher than that of the C ashes.

This will have direct impact on the air entraining operationsPrasanth Tanikella - Purdue University 38

Task 5 – Development of a database

• An electronic database would be developed as shown here

• Draw down menu for all the fly ashes to extract the data will be provided

• The database would contain the chemical and physical characteristics of fly ashes along with the SEM pictures and XRD patterns


Task 6 – Report Writing

• A draft final report has been prepared and can be provided to the SAC for review

• The report contains all the details of the original project, methods of examination, the results, a comprehensive discussion and a conclusion section. However, the data base section has not yet been completed


Phase II - Evaluation of the hydration characteristics of cement-fly ash binder systems

• When used as a substitute for part of the cement, fly ash offers a lot of benefits, both in terms of early and later hydration characteristics and in terms of the economy

• As seen earlier, no two fly ashes are entirely similar with respect to their chemical and physical properties

• As a consequence, their incorporation into cementitious binder systems can result in highly variable hydration characteristics

• It is important to understand and estimate the properties of cement-fly ash binder systems for its field application

• In addition, we can also estimate the amount and type of fly ash(s) to be added to the binder system to achieve some required properties using models that account for variable characteristics of the fly ashes


Phase II - Evaluation of the hydration characteristics of binders

A rational basis for the modeling approach is that the model is based entirely on the fundamental physical and chemical characteristics of the components

The early hydration characteristics of binder systems, which can be statistically modeled, would be helpful in choosing the right type and the right amount of fly ashes for field applications. These include:- Setting time- Pozzolanic activity index- Amount of heat generated- Peak heat of hydration- Time after mixing when the peak occurs- Degree of hydration


Phase II - Materials and Proportions

• Type I portland cement manufactured by Buzzi Cement in Greencastle, Indiana

• Binary binder systems with a fly ash replacement of 20% by weight

• Ternary binder systems with a combined fly ash replacement (two fly ashes) of total 20% by weight

• Water to binder ratio of 0.41, kept constant throughout


Phase II - Tests methods and Techniques

Setting time – Performed according to ASTM C 191 Heat of hydration – Isothermal calorimetry Strength activity index – Performed according to ASTM C 311 Pore structure – Mercury intrusion porosimetry Non-evaporable water content – Using the LOI technique Degree of hydration

Glass content in fly ashes – Two techniques are being looked into

A thorough statistical analysis of the data will be performed and a statistical model for the above properties will be developed based on the significantly affecting physical and chemical properties of the fly ash and cement


Estimation of the Glass Content

• Glass is the amorphous content in fly ash• The reactivity of the fly ash depends on the amount of glass present and its

composition• Two techniques are being investigated for the quantitative estimation of

the glass content in fly ash• Quantitative estimation of glass in fly ash using infrared

spectroscopy• Method was applied to slag and the results were satisfactory• Ref: A. R. N. Ebrendu, K. E. Daugherty, The quantitative estimation of glass in slag by infrared

spectroscopy, Cem. and Concr. Res, Vol. 14 (1984), pp 873-883

• Quantitative estimation of glass in fly ash using QXRD analysis• The amorphous portion of the fly ash can be estimated using the Rietveld-

based SIROQUANT technique• Two techniques were investigated,

- XRD analysis of samples spike with known masses of synthetic corrundum or zinc oxide- Analysing the raw or unspiked fly ash directly using SIROQUANT technique

• Ref: Colin R. Ward, David French, Determination of glass content and estimation of glass composition in fly ash using quantitative X-ray diffractometry, Fuel 85 (2006) 2268-2277Prasanth Tanikella - Purdue University 46


Original Project Task 1 - Literature Review Task 2 - Collection of Specimen Task 3 - Characterization of available fly ashes - Methods of examination - Results Task 4 - Data analysis and conclusions Tasks 5 & 6 - Report writing and Database developmentProposed Expansion Evaluation of the hydration characteristics of binders Binary binder systems Ternary binder systems Summary and conclusions of the study


Binary Binder Systems

• Binary binder systems include Type I portland cement replaced by a fly ash at 20%

• Water to binder ratio kept constant at 0.42


Experimental Design - Binary binder systems

• All the available 20 fly ashes will be tested for all the aforementioned properties

• Data is collected, processed and is used for statistical modeling

• Statistically significant variables (chemical and physical properties of the binder system) affecting a specific property are found and their relevance to the property is established

• Statistical models will be developed using these statistically significant variables for all the properties


Results – Setting time

• The initial setting time for all the binary binder systems was found out according to ASTM C 191. Normal consistency of each paste was measured and is used for measuring the setting time of the pastes

• The setting time for the cement paste was found to be 2.73 hours at a consistency of 0.265 water/binder ratio


Statistical Analysis – Setting time

• There is a significant variation found in the setting times, in both the classes of fly ashes

• The correlation coefficients for set time with other variables for all the fly ashes are shown below (significant ones are highlighted in green)

• No significant correlation of set time with any of other variables



• The correlation coefficients for set time with other variables for class C fly ashes is shown below

• There are significant correlations of set time with other variables, shown in yellow

• Strength activity index (SAI) is also correlated with a few variables



• The correlation coefficients for set time with other variables for class F fly ashes is shown below

• Not many significant correlations of set time with other variables• Model built with correlated variables which might not be significant• Notice that the pozzolanic activity index (PAI) is correlated with set

time


Modeling – Setting time

• A preliminary model for set time with other variables for class C fly ashes is shown

• Variables – Sulfate and (Sulfate)3x(Alumina) = S3A

• Highly significant model (p-value < 0.01)

• Not so good R2 Value – 0.6456• Not significant variables (p-

values > 1)

• Significant error• Scope to improve the model

using various functions and standardizing variables


Modeling – Setting time

• A preliminary model for set time with other variables for class F fly ashes is shown

• Variables – Sulfate and (sulfate)x(Alumina)3 = SA3

• Not significant model (p-value > 0.01)

• Not so good R2 Value – 0.6725

• Not significant variables (p-value >0.01)

• Significant error• Scope to improve the model

using various functions and standardizing variables


Modeling – Inferences

General scope for improving the set time model

• Consider the chemical composition of the entire binder system• Explore the possibilities of including more variables, which

theoretically affect the dependent variable (set time)• Include the glass content and composition of the fly ash

Models for other measurable variables

• Setting time measurement is more arbitrary compared to any other measurable property

• Accurate definition and measurement for all the other properties including heat of hydration, porosity, unhydrated fly ash


Ternary Binders

• Binders with cement and two different fly ashes, including both Class F and Class C ashes

Advantages over a binary system• Can choose two different fly ashes in the available suite, with

different chemical and physical compositions and mix in various proportions to obtain a binder with required characteristics

Disadvantages• More intensive and cumbersome modeling process• We can expect more errors in the prediction• Other factors, including the mixing procedure of the fly ashes

might affect the properties


Available Statistical Techniques

Full factorial design- Very cumbersome to apply for a large amount of data- 20 fly ashes lead to a number of combinations of 190 at a specific proportion- More effective model with reduce error in prediction

Fractional factorial design (Taguchi method)- Reduces the number of experiments to be performed drastically- Requires about 18 runs for each of the property, depending on the number of significant variables- Model can be as accurate, prediction might have a slight additional error


Orthogonal Arrays – Taguchi Method

Standard tables, known as orthogonal arrays are used for the design of experiments

The chosen performance characteristic is analogous to the “signal to noise ratio” instead of the average value to interpret the trial result data

This ratio represents the scatter around the target


Evaluating setting time using orthogonal array

Factors affecting the property are identified, using both statistical and analytical methods

The factors are chosen at three different levels, depending on their mean value and the range of values

The experimental design is based on the number of factors and the number of levels

Typical test matrix for a four factor and three level experimental design is shown

Full factorial technique gives a set of 81 experiments for the same

ANOVA is used to build a modelPrasanth Tanikella - Purdue University 61

A sample test matrix for the above factors and levels

Significantly affecting variables for setting time

Conclusions – Phase 2

• The current study is aimed at statistically modeling the hydration properties of binary and ternary binders systems

• A comparison of the two models will be made, including a statistical testing of the ability to use the binary model to ternary mixes

• A binary binder model for setting time is developed and its refining would be done after consulting the Statistics Department, Purdue University

• The experimental technique to model the ternary binder system has been established and will be confirmed after consulting with the Statistics Department, Purdue University

• The outcome of the project would be a program which predicts the early age properties of binary and ternary binder systems

• The program would also be able to estimate the type and amounts of fly ash to be added to cement to achieve certain desired early age properties


Project Timeline

Brown – Original proposed tasks Green – Tasks completed Yellow – Future tasks


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