MASTER'S THESIS DEFENSE PRESENTATION (Sept 16)

US Army Corps of Engineers
BUILDING STRONG®

Innovative solutions for a safer, better worldBUILDING STRONG®
Background: The State of the Art &
Path Moving Forward
 Issues Surrounding Portland
Cement Concrete
► Reduced Carbon Footprint
► High Firing Temperature
• Approximately 1400°C
 Alternative Binding Materials
► Geopolymers
 Motivations
► Weak Chemical Bonding
► Corrosion Mitigation
2
Figure 1. Corrosion of steel reinforcement bar
(courtesy of buildingfacades.com)
Figure 2. “The Concrete of Tomorrow.” By-
products of other processes and materials
serving as reasonable alternatives to PCC.
(courtesy of civilengineeringforums.com)

Scope of Current Research
 Previous Research Efforts
► Weiss et al. (2009)
► Allison et al. (2012)
► Moser et al. (2013)
 Objective of This Study
► Study interaction between novel
enamel coatings and various
geopolymeric matrices
3
Vitreous
Enamel
Pozzolanic
Materials
Novel
Material
Figure 2. Vitreous
enamel coated pin
(courtesy of Moser
et al. (2013)
Figure 1. Test rods having cement
applied to melted glass at the
surface of the rods (courtesy of
Weiss et al. (2009)

Materials Utilized During This Research
 Fiber Types
► Straight
• Fibercon International
CAR-25-CDM
► Kinked
• Dramix ZP 305
► Undulated
• Nycon-SF Type V High
Performance Steel Fiber
 Coatings
► Ferro SI-677 A Black Ground
Coat
 Matrix Materials
► Fly Ash
► Metakaolin
► Portland Cement
4
Figure 1. CAR-25-CDM
(straight fibers)
Figure 3. Dramix ZP 305
(kinked fibers)
Figure 2. Type V High Performance
(undulated fibers)
Figure 4. Matrix materials were fly ash (left),
metakaolin (middle), and portland cement (right)

Specimen Preparation: Application
of Reactive Vitreous Enamel Coating
5
Fibers were cleaned using ethyl alcohol
to remove oils and impurities
Fibers then dipped in fresh enamel for a vitreous
coating. Afterwards, pozzolans were applied for
RVEC fibers.
Placed in furnace at 811°C
for 2.5 minutes to harden to
coating

Specimen Preparation: Embedment
of Coated and Uncoated Fibers
6
Coated and
uncoated fibers
mounted onto
fiber platform
Mounting cups
filled with fresh
mortar and fibers
embedded
Fiber embedded
specimens cured
for 28 days

Experimental Methods: Mechanical
& Chemical Characterization
 Pullout Testing (mech.)
 Push-out Testing (mech.)
 Scanning Electron
Microscopy (SEM)
 Energy Dispersive X-ray
(EDX) (chem.)
7

Experimental Methods: Fiber Pullout
Testing
 Instron 4206 30k Universal
Testing Machine
► 1kN Load Cell
 Pullout rate of 0.05 inch min-1
(0.021 mm sec-1 )
 Failure of fibers prior to failure of
the bond between the fiber and
matrix
 Push-out testing was then
considered as a potential
alternative.
8
Figure 1. Overall setup
employed to perform
pullout testing
Figure 2. Fiber remaining in
grips of Instron machine
once the pullout test had
concluded

Experimental Methods: Push-out Testing
 Fiber Push-Out Test
9
A mechanical test performed to measure the
matrix/fiber interface de-bonding energy and the
effects of frictional sliding between the matrix and
the fiber.

Experimental Methods: Push-Out
Testing (cont.)
10
 Struers DuraScan-70 Fully
Automatic Hardness Tester
► 0.098 N (10 gf) to 98.10 N (10 kgf)
load capacity
 Interface 1500 Low Capacity
LowProfile™ Load Cell
► 250 N load capacity
 Aluminum Platen
 ecos Workflow software
package
 MicroPunch data acquisition
script (developed by ERDC
personnel)
Struers DuraScan-70
hardness tester
Interface 1500 Load Cell
(blue) with aluminum platen
mounted atop (silver)

Testing (cont.)
 Determine the site where
testing will be conducted
 Push-out test is perform on the
fiber at the center of a sample
 Verification of push-out by
visual inspection
11
Specimen during Push Out
testing
Specimen after testing

Experimental Methods: SEM and
EDX Spectroscopy
 Polished sample
► Requires special
preparation
 FEI Nova NanoSEM 630
field emission SEM
► 15 kV voltage source
► Backscattered electron
detector
 Bruker Quantax AXS
solid-state EDX detector
12

Results & Discussion: Pullout
Testing
13
Comparison of the pullout testing results of
uncoated and coated kinked fibers embedded
in metakaolin and fly ash-based geopolymer
mortars.
Comparison of the pullout testing results of
uncoated and coated undulated fibers
embedded in metakaolin and fly ash-based
geopolymer mortars.

Results & Discussion: Pullout Testing (cont.)
14
Comparison of the pullout testing results of uncoated and coated
straight fibers embedded in metakaolin and fly ash-based
geopolymer mortars.

Results & Discussion: Optical
Microscopy of Fibers Post-Pullout Test
15
An uncoated straight fiber that had been
embedded in fly ash-based geopolymer
mortar and pulled out completely during
pullout testing.
A reactive vitreous enamel coated kinked
fiber that had been embedded in fly ash-
based geopolymer mortar and exhibited
necking during pullout testing.

Microscopy of Fibers Post-Pullout Test
(cont.)
16
A reactive vitreous enamel coated undulated fiber that had been embedded in
fly ash-based geopolymer mortar and exhibited necking during pullout testing.
(a) Flat, rigid side of the undulated fiber and (b) the undulated, smooth side of
the same fiber.
a b

Small Study: Tensile Tests Performed on
Each Fiber Type Under Various Treatments
 Three treatment
configurations
► Untreated (no heat)
► Annealed (811ºC)
► Quenched in tap water
immediately following
heat exposure (811ºC)
 Exposure to heat resulted in
approximately 40 – 60%
decrease to tensile strength
for each fiber type.
17

Lessons Learned from Pullout
Testing…
18
• Not the most efficient method of
evaluating bond strengths
• Heat exposure decreased fiber
tensile strengths
• Fibers failed prematurely
• Evident by necking of fibers
• Find an alternative technique of
evaluating bond strength

Results & Discussion: Push-Out
Testing
19
Uncoated straight fibers embedded in fly ash-based geopolymer
mortar that has undergone push-out testing.
Reactive vitreous enamel coated straight fibers embedded in
fly ash-based geopolymer mortar that has undergone push-
out testing.
Fly Ash Specimens, Uncoated, 1.0 mm Fly Ash Specimens, Coated, 1.0 mm

Results & Discussion: Push-Out
Testing (cont.)
20
Note the change in behavior of curves a & b versus that of curves c & d.
a
b d
c

Microscopy of Push-Out Specimens
21
An uncoated straight fiber embedded in metakaolin-based
geopolymer mortar that has undergone push-out testing.
A reactive vitreous enamel coated straight fiber embedded in
metakaolin-based geopolymer mortar that has undergone
push-out testing.

Results & Discussion: Avg. Bond Strengths of Fibers
(Fly Ash-Based Geopolymer Mortar)
22
0.00
5.00
10.00
15.00
20.00
25.00
1.00 1.50 2.00
Avg.BondStrength(MPa)
Sample Thickness (mm)
Uncoated Fibers
Coated Fibers

Results & Discussion: SEM Imaging of Sample
(Metakaolin Coated)
23
Overview of metakaolin-based geopolymer mortar
(200x mag.)
Interface between metakaolin-based geopolymer paste and
sand particle
(1,000x mag.)

(Metakaolin Coated) (cont.)
24
Reactive vitreous enamel coated fiber
(Overview of entire site of embedment)
(200x mag.)
Matrix-coating Interfacial Transition
Zone (ITZ) of a coated fiber
(1,000x mag.)
Microcracking at the matrix-coating ITZ
of a coated fiber
(4,000x mag.)

(Metakaolin Coated) (cont.)
 At the matrix-coating interface,
pronounced chemical shrinkage is
observed.
 Shrinkage is not isolated only to
this interface. This characteristics
to prevalent throughout the entire
matrix.
 This shrinkage is the main reason
for the decreased bond strength
values.
► The shrinkage cracking is effectively
de-bonding the coated fiber from the
metakaolin matrix at the interface.
25
Chemical Shrinkage Crack
Metakaolin Matrix Vitreous Enamel

Results & Discussion: Energy Dispersive X-ray
(EDX) Spectroscopy
(Metakaolin Specimen)
26
Line scan and elemental mapping of Matrix-Enamel-
Fiber Interfacial Transition Zones (ITZs)

(Cement Coated)
27
Straight Steel Fiber
Vitreous
Enamel
Reactive Topcoat
(cement)
The image above is an expanded
view of the portland cement control
matrix.

(Cement Coated) (cont.)
28
Fiber-Vitreous Enamel Interface
Straight Steel Fiber Fiber-Enamel
Interface
Vitreous Enamel
Reactive Vitreous Enamel-Cement Matrix
Interface
Vitreous Enamel
Reactive
Vitreous
Enamel Coating
Coating-Matrix
Interface
Portland
Cement Matrix

(EDX) Spectroscopy
(Cement Specimen)
29
Line scan and elemental mapping of Matrix-Enamel-Fiber
Interfacial Transition Zones (ITZs)

(Fly Ash Coated)
30
Overview of fly ash-based geopolymer mortar matrix
(200x mag.)
Reactive vitreous enamel coated fiber (Overview of entire
site of embedment)
(200x mag.)

(Fly Ash Coated) (cont.)
 The white particles throughout
the enamel have elemental
compositions consistent with
that of chromium.
► Chromium oxide particles
 The appearance of separation
at the Enamel-Matrix ITZ is
actually less than perfect
polishing.
31

(EDX) Spectroscopy
(Fly Ash Specimen)
32
Line scan and elemental mapping of Fiber-Enamel-
Matrix Interfacial Transition Zones (ITZs)

Results & Discussion: Energy Dispersive
X-ray (EDX) Spectroscopy
33

Conclusions
 Reactive vitreous enamel coating enhances bond strength on
the order of up to 5.7 times
 EDX spectroscopy shows smoother transitions in elemental
composition across the ITZs of coated specimens, translating to
these higher bond strengths
 Overall toughness is increased in cementitious samples
containing coated fibers versus those with uncoated fibers
 Higher standards of deviation in coated samples are as a result
of the non-uniformity of the coating
 Overly thick coating negates mechanical anchorage in fibers of
deformed geometries
34

Future Work
 Nanomechanical
characterization of
reactive vitreous enamel
coated fibers
 Uniform application of
coatings to fiber
reinforcement
 Effects of pore size
distribution on bond
strength
35
Nanoindentation of ITZ between fly ash-based geopolymer and
steel (courtesy of Allison et al. (2015))

Acknowledgements
U.S. ERDC Personnel
 Dr. Charles A. Weiss, Jr., GSL
 Dr. Robert D. Moser, GSL
 Henry Blake, ITL
 Kevin Torres-Cancel, GSL
 Brett A. Williams, GSL
 Jason Morson, GSL
 Wendy Long, GSL
 Stephen Murrell, GSL
Jackson State Personnel
 Dr. Lin Li
 Dr. Fashard Amini
 Dr. Wei Zheng
 Shanetta Cristler
36
I’d like to thank the ERDC 6.1 Military Engineering Basic Research
Program for providing the funding necessary to execute the research
presented herein.

Thank You For Listening!
 Questions???
 Comments???
37

Testing (cont.)
 Using the EcoWorks software,
center the platen underneath
the Overview Camera (OC).
 After naming the sample and
indicating testing parameters
(i.e. load), use the Evaluation
Camera (EC) to focus and find
center of hole in platen.
 The hole was drilled in an
effort to insure that the bottom
of a fiber isn’t obstructed
during push out testing.
38
Evaluation Camera view of the center of hole in platen

Push Out Test Procedure Overview
(cont.)
 The EC is then raised and the
push out specimen is placed
on the platen with the fiber
positioned over the hole.
 Afterwards, the site of
indentation is established
using the program. Should be
as close to the center as
possible.
39
Evaluation Camera view of the center of
a fiber.
Overview of push-out test setup
including a sample prepared for testing.

(Metakaolin-Based Geopolymer Mortar)
40
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
1.00 1.50 2.00
Avg.BondStrengths(MPa)
Uncoated Fibers
Coated Fibers

(Portland Cement Mortar)
41
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
1.00 1.50 2.00
Avg.BondStrengths(MPa)
Uncoated Fibers
Coated Fibers

MASTER'S THESIS DEFENSE PRESENTATION (Sept 16)

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