Advanced Cement-Based Sustainable Material Technology
Transcript of Advanced Cement-Based Sustainable Material Technology
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Advanced Cement-Based Sustainable Material Technology
Zongjin LiHong Kong University of Science and Technology
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Characterization and measurementIntroductionDestructive methodsNon-destructive methods-Elastic wave method-Infrared thermal method-Non-contact resistivity method-Dynamic modulus method-Ellipse ring for crack sensitivity
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IntroductionDestructive test – obtain the
material properties by seriously destroying sample
Nondestructive test – obtain the information without damaging samples
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Introduction-nondestructiveQuality control
Finished productsInjection of groutPosition of reinforcing steelWelding of reinforcing steelHydration rate of fresh concreteSelection of watermelon and eggs
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Introduction-nondestructiveb. In-service inspection
Boiler and vesile safety monitoringBridge safety monitoringBuilding finish monitoringAirplane
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Destructive tests -
Control methods for strength test
Open Loop Control (OLC)Close Loop Control (CLC)
Input variable(Reference Input)
Prescribed functionController Controlled Process
Output variable
Measured Output
Input variable(Reference Input)
Prescribed functionController Controlled Process
Output variable
Measured OutputFeedback Signal
Open Loop Control (OLC)
Closed Loop Control (CLC)
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Destructive tests -
Calibration of transducers (1)
a. Mechanical parameters: Displacement, Strain, Crack opening, Force
b. Electric parameters: Voltage, Capacity, Impedance, Current
c. Calibration:Find relationship between electrical variables and mechanical variablesGeneral procedures
Connect the transducer to be calibratedProvide a known mechanical parameter outputAdjust the reading of transducer to a desired value
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c. Calibratione.g. A displacement transducer of 2.5mm full range
Destructive tests -
Calibration of transducers (2)
Displacement:
Voltage:
0.25
. . . .
0.5
. . . .
1.25
. . . .
2.5mm
1 . . . .
2
. . . .
5
. . . .
10V
V
D (mm)
k
10
2.5
For measurement:
Displacement = = C V
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Destructive tests-
Compressive test (2)
Typical load versus axial displacement and load versus circumferential Displacement curves for three classes for concrete
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Load cell
Machine wedge grip
Loading fixture
Aluminum
LVDT{1 LVDT{3
loading plate
LVDT{4
Aluminumloading plate
LVDT{2
Loading fixture
Machine wedge grip
Machine actuator
Destructive tests –Tension test
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0.00 0.02 0.04 0.06 0.08 0.10
Displacement (mm)
0
1
2
3
4
5
Steel fiber (0.5% in volume)
Polypropylene fiber (0.5% in volume)
Plain concrete
Destructive tests –Tension test
16shear waves: do not propagate in liquids
Case 1: concrete is liquid
no wave transmission at interface
Case 1: concrete is liquid
no wave transmission at interface
fresh concrete
steel plateshear wave transducer (2.25 MHz)
Principle of Shear Wave Reflection Method
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Principle of Wave Reflection
fresh Concrete
Case 2: concrete is hardening
transmission losses at interface
Case 2: concrete is hardening
transmission losses at interface
hardened concrete
steel plateshear wave transducer (2.25 MHz)
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Signal Analysis
Reflection Factor r
F1 , F2 …. FFT of reflections at 2.25 MHzL …. Losses (material, coupling, geometry)
F2 (f)F1 (f)
= L · r
Attenuation of Wave Reflections
Attenuation (dB) = - 20 · log (r)
Time Domain Frequency Domain
R1
R2
F2
F1
FFT
2.25 MHz
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Typical Reflection Loss Development
Phase 1: liquid concrete no reflection loss
Phase 2: concrete hardens attenuation increases
Phase 3: hardening continues attenuation approaches final value
Ref
lect
ion
Loss
Phase 1 Phase 2
Point A
Phase 3
Point B
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Point A – Initial Setting
0
2
4
6
8
10
2 3 4 5 6Time of point A (hours)
Initi
al s
ettin
g tim
e (h
ours
)
PlainSilica
Superplasticizer
Accelerator
Retarder
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0
10
20
30
40
50
0 1 2 3 4
RL
vs. Strength
w/c = 0.35w/c = 0.6
w/c = 0.5
R2 = 0.97
R2 = 0.92 Transition Pointbetween 6 – 15 hours
Cement Mortarsdifferent w/c-ratios
Com
pres
sive
Stre
ngth
(MP
a)
Reflection Loss (dB)
22Transducer Central Power Supply
Main Power Switch
Laptop Computer
Pulser/ Receiver
Temperature Logger
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Result of Field Test
0
10
20
30
40
50
0 12 24 36 48
Equivalent Age (°C h)
Stre
ngth
(MPa
)
strength determined in ACBM lab (precalibration)
strength determined in plant (cylinder test at 16h)
quality controlprecast plant
calibrationACBM-lab
strength measured by wave reflection method
NDT-method
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Pulse VelocityDetermination
Amplitude Threshold
to – Onset time of signal
AT
TimeAm
plitu
de
Relationships
( )( )( )2ν1ν1ρ
ν1EvP −+−
=
( )ν12ρEvS +
=
P-waves
S-waves
Velocity ~Density, ρE-Modul, EPoisson's Ratio, ν
Time Domain
d
tdvΔ
=
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Pulse Velocity Measurements
from Reinhardt, Grosse, University of Stuttgart
Sensitivity to hydration rate influenced by retarder
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Embedded sensor
Function generator
Poweramplifier
Pre-
amplifier
Oscilloscope
Transmitter Receiver
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Dynamic modulus and Poison’s ratio
2LCE ρ= 1
2 2
2
−=T
L
CCυ
Where,and are longitudinal and transverse
velocities, respectively. is the density of the concrete specimen.The calculated result fit well with the dynamic Young’
modular measured by standard method.
LCTC
ρ
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Hydration monitoring using embedded sensor
传感器埋置
监测中33
In situ and real time monitoring
Life time healthy monitoring
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AE techniqueAE technique is a passive NDT method. It relies on the detection of elastic waves generated by sudden release or change of energy or deformation in materials.
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AE source location For 3-D case
Sum of the square of the errors( ) ( ) ( ) ( ) ( ) ( ) Ctzzyyxxzzyyxxe iiiii 1
22221
21
211 Δ−−+−+−−−+−+−=
( )
( )∑
∑
=
=
Δ−−=
=
n
iii
n
ii
Ctdd
ee
2
211
2
21
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AE source locationDifferential with respect to x, y, z and C are in forms of;
( )
( )iCΔtddd
xxd
xxxeCx,y,zf
i
n
i i
i
x
112 1
12
,
−−⎟⎟⎠
⎞⎜⎜⎝
⎛ −−
−=
∂∂
=
∑=
( )
( )iCΔtddd
yyd
yyyeCx,y,zf
i
n
i i
i
y
112 1
12
,
−−⎟⎟⎠
⎞⎜⎜⎝
⎛ −−
−=
∂∂
=
∑=
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AE source location
( )
( )iCΔtddd
zzd
zzzeCx,y,zf
i
n
i i
i
z
112 1
12
,
−−⎟⎟⎠
⎞⎜⎜⎝
⎛ −−
−=
∂∂
=
∑=
( )
( )∑=
−+ΔΔ=∂∂
=n
iiii
C
ddCttCeCzyxf
21112
,,,
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Accelerated corrosion test
Concrete
3% NaCleletrolyte
Plexiglasspool
Rebar
To AE system
AEsensorPreamplifier
Resistor
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AE source location
Computation of corrosion position
Lx
Transducer TransducerRebar corrosion
( )
2
2tCLx
CxLCtxxL
Δ−=
+Δ=−⋅Δ=−−
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Infrared thermograph --Introduction (1)
a) LightAn electromagnetic wave and travels at
3x108 m/s
EM waves can be either visible or invisible according to their wavelength
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Infrared thermograph --Introduction (2)
b) Visible light frequency rangeWave length (nm) Color400-450 violet450-480 blue480-510 blue-green510-550 green550-570 yellow-green570-590 yellow590-630 orange630-700 red
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Infrared thermograph --Introduction (3)
c) Invisible EM Waves
Wavelength λ < 0.4 μ m == ultraviolet0.7 μ m < λ < 1.5 μ m == near-infrared1.5 μ m < λ < 20 μm == mid-infrared20 μm < λ == far infrared
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Infrared thermograph --Mechanism (1)
Emission of EM waves by objects(The principle of blackbody radiation)Any object at non-zero temperature emits
EM waves
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Infrared thermograph --Mechanism (2)
Infrared radiation and temperature relatedThe wavelength of ITC is within the emission wavelength range of any object in the normal temperature range of -30oC to 100oC.Defects underneath can be detected by measuring the slight temperature fluctuation over the surface of an object.
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Theoretical background for debonded tile detection (1)
B - Heat capacitanceH - Heat flow rateK - Thermal conductivity
Initial condition:t=0, T=T0
)( 0TTKHdtdTB −−=
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Theoretical background for debonded tile detection (2)
For heating process (H>0)
For cooling process (H<0)
⎟⎟⎠
⎞⎜⎜⎝
⎛−+=
− tBK
eKHTT 10
⎟⎟⎠
⎞⎜⎜⎝
⎛−−=
− tBK
eKH
TT 10
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Two Cases (1)Two cases for voids between tile and
substrateCase 1 = = voids are filled with waterCase 2 = = Voids are empty (filled with air)
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Two Cases (2)
Heat Capacity(J cm-3
C-1)
Conductivity(W m-1
C-1)Material
Air
Concrete
Water
0.0008
1.9
4.2
0.024
1
0.6
Thermal Properties
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Two Cases (3)Case 1: Gap filled with water
During Heating proces
H/K K/BConcrete H ~1/1.9≈0.5Water 1.6H ~1/7 ≈0.14∴T is lower than concreteDuring Cooling processT is higher than concrete
⎟⎟⎠
⎞⎜⎜⎝
⎛−+=
− tBK
eKHTT 10
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Two Cases (4)Case 2: Gap filled with air
During Heating proces
H/K K/BConcrete H ~0.5Water 42H ~30∴T is higher than concreteDuring Cooling processT is lower than concrete
⎟⎟⎠
⎞⎜⎜⎝
⎛−+=
− tBK
eKHTT 10
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Two Cases (5)
A debonded tile sample with half air and half wateruniform heating of the inspected faceafter cooling for half an hour.
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Examples (1)
Thermal image of HKUST library indicating defected area
filled with water on the external tiled wall
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Examples (2)
Thermograph of the government staff quarter under
sunshine - indicating heavy damage on external wall
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Reflection correction
where
ε = object emissivity (the object is considered opaque)
ρ = object reflectivity
Nobj = radiance from the surface of the object
Nenv = radiance of the surrounding environment
envobjCAM NNN ρε +=
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Reflection correctionHigh emissivity case (ε > 0.9. ε = (1-ρ))
Nobj ≈
NCAM
Low emissivity case (ε < 0.9)Reflection should be considered
Ceramic tile case (ε = 0.6 - 0.8)Reflection can not be neglected
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Distance and angle --Space resolutionField view of an ITC depends on the lens of the systemA camera may consist of 320 x 240 detectors in an arrayThe area covered by each detector is the smallest size of an object Instantaneous field of view (IFOV)
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Distance and angle - Space resolutionExample (20 degree by 15 degree lens)
Distance to object Field of view IFOV
1m 0.35 x 0.26 m 1.1 x 1.1mm
5m 1.76 x 1.32 m 5.5 x 5.5mm
10m 3.52 x 2.63 m 11 x 11mm
50m 17.6 x 13.2 m 55 x 55mm
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Distance and angle - Influence of angleThumb rule for reality - No [erfectly diffuse bodies exist- For most bodies, the emissivity uually goes down from 50 degree from normal
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Cement conduction mechanism
cationanion
anodecathode
Conduction in cement is essentially electrolytic via ion transport through the interconnected pore network.
Resistivity
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ρ= Rtotal π2h[ ln(r3/r2) +
34
4
rrr−
ln(r4/r3) -12
1
rrr−
ln(r2/r1)]
Analytical solution of resistivity
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ProceduresWeighing and mixing
water and cement at
w/c=0.3, 0.35, 0.4 for 4 minutesConsequently, casting
into electrical
resistivity mouldRecording
the data at sampling interval 1
minute and stop at or after 24 hoursMeasuring
the weight and height of the
sampleAnalyzing
in EXCEL and smooth/
differential in Origin to get dρ/dt
curve and get the maximum dρ/dt
point
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0 20 40 60 80 100 120 140 160 180 200 2200.730.740.750.760.770.780.790.800.810.820.830.840.850.860.870.88
L(t(l),ρ(l))
L(t(l),ρ(l))
L(t(l),ρ(l))
IIIM(t(m),ρ(m))
M(t(m),ρ(m))
M(t(m),ρ(m))
III
P0.5
P0.4
P0.3
Ele
ctric
al re
sist
ivity
(Ω.m
)
Time (min)
Typical resistivity curve
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18
6
Elec
trica
l res
istiv
ity (O
hm.m
)
02 4 6
2
4
time (hours)128 10 14 16
Elec
trica
l res
istiv
ity ra
te (O
hm.m
/h)
0.3
2420 220
0.1
0.2
M
P1
P2
L
88
18
6
Elec
trica
l res
istiv
ity (O
hm.m
)
02 4 6
2
4
time (hours)128 10 14 16
Elec
trica
l res
istiv
ity ra
te (O
hm.m
/h)
0.3
2420 220
0.1
0.2
M
P1
P2
Dyna. bala. Setting Hardening Hardening decelerationDissolution
L
90
Penetration method for setting time
Initial setting:Penetration resistance:
3.5 MPa
Final setting:Penetration resistance:
28
MPa
(ASTM 403)
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t = g (t , t ) (2)
t = f (t , t ) (1)
The relationship for the resistivity response and setting time
~t (log scale)
tm
fin
ini
m
m
t
t
tt
electrical resistivity response
~t
t and t fromm t
init tfin
t and t frompenetration resistance
PR~t
ini fin
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tfin =0.9202tt +0.2129
Accelerator
SP1
ControlHigher W/C
0
5
10
15
20
0 5 10 15 20
tt (hour)
t fin (
hour
)
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t = g (t , t ) (2)
t = f (t , t ) (1)
The relationship for the resistivity response and setting time
~t (log scale)
tm
fin
ini
m
m
t
t
tt
electrical resistivity response
~t
t and t fromm t
init tfin
t and t frompenetration resistance
PR~t
ini fin
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0
5
10
15
20
0 2 4 6 8 10 12 14 16 18
Measured tini and tfin (hours)
Cal
cula
ted
t ini a
nd t
fin (
hour
s)
tini
tfin
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Mixing, sieving to get mortar, casting
Remove bleeding water
Penetrate mortar to25 ± 2mm for each time
Test one time once 30 minutes, and then 15 minutes
Plot graph resistance ~ elapsed time
Mixing, casting
Automatically and continuously record data
Plot graph resistivity ~ elapsed time
Hard work
Quite long time
Penetration resistance Electrical resistivity
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Relationship between resistivity and strength
y = 5.1538x - 17.098R2 = 0.9731
0
10
20
30
40
50
0 2 4 6 8 10 12
Resistivity (ohm.m)
Com
pres
sive
stre
ngth
(MPa
)
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Dynamic modulus
Induce an impact
Accelerator receive the vibration response and transfer them to the Data Acquisition Unit
Frequency display on the Signal Analysis Unit
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Accelerometer
Cylindrical specimen
Steel sphere
Armor plate
OscilloscopeVolts
Time
FFT
Waveform analyzer
FrequencyMagnitude
Dynamic modulus
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Results
0 5 10 15 20 25
4.704
8.992
Frequency (kHz)
Mag
nitu
de
W/C=0.5 8.0 Hours
0 5 10 15 20 25
5.408
10.34
Frequency (kHz)
Mag
nitu
de
W/C=0.5, 0.5-Day
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0 5 10 15 20 25
7.802
14.912
Mag
nitu
de
Fequency (kHz)
W/C=0.5, 1.0-Day
0 5 10 15 20 25
8.512
16.384
Frequency (kHz)
Mag
nitu
de
W/C=0.5, 2.0-Day
Results
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0 5 10 15 20 25
8.832
16.896
W/C=0.5, 3.0Day
Mag
nitu
de
Frequency (kHz)0 5 10 15 20 25
10.048 kHz
19.296 kHz
W/C=0.5, 28.0-Day
Mag
nitu
de
Frequency (kHz)
Results
104
11
21
2
1
21 C
ffB
ffA +⎟⎟
⎠
⎞⎜⎜⎝
⎛+⎟⎟
⎠
⎞⎜⎜⎝
⎛=ν
where
478.12443.246457.82
1 −⎟⎠⎞
⎜⎝⎛+⎟
⎠⎞
⎜⎝⎛−=
DL
DLA
172.5672.101599.342
1 +⎟⎠⎞
⎜⎝⎛−⎟
⎠⎞
⎜⎝⎛=
DL
DLB
731.6298.105681.342
1 −⎟⎠⎞
⎜⎝⎛+⎟
⎠⎞
⎜⎝⎛−=
DL
DLC
(1)
Poison’s ratio
105
0 4 8 12 16 20 24 280.00
0.05
0.10
0.15
0.20
0.25
0.30
W/C = 0.5, Plain Concrete
W/C = 0.6, Plain ConcretePois
son'
s rat
io
Age (Days)
Poison’s ratio
106
( )2
101 212 ⎟⎟
⎠
⎞⎜⎜⎝
⎛+=
nd f
RfE πρν
where
( ) ( ) 222
21 CBAfn ++= νν 3791.15868.00846.0
2
2 +⎟⎠⎞
⎜⎝⎛−⎟
⎠⎞
⎜⎝⎛=
DL
DLB
1093.24585.12792.02
2 −⎟⎠⎞
⎜⎝⎛+⎟
⎠⎞
⎜⎝⎛−=
DL
DLA 3769.37026.1285.0
2
2 +⎟⎠⎞
⎜⎝⎛−⎟
⎠⎞
⎜⎝⎛=
DL
DLC
(2)
Dynamic modulus
107
Dynamic Modulus
0 10 20 300
10
20
30
40D
ynam
ic m
odul
us o
f eal
stic
ity (G
Pa)
Age (Days)
W/C = 0.5, Plain Concrete
W/C = 0.6, Plain Concrete
108
0 4 8 12 16 20 24 280
10
20
30
40M
odul
us o
f Ela
stic
ity (M
Pa)
Age (Days)
Static modulus of elasticity
Dynamic modulus of elasticity
Static and dynamic modulus
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Cracking time of mortars with NaOH and KOH (w/c=0.45)
00.050.1
0.150.2
0.250.3
0.350.4
0.450.5
0 1000 2000 3000 4000 5000 6000
Time (min)
Res
istan
ce (M
Ohm
) 2356
Crack sensitivity test