View
225
Download
4
Category
Preview:
Citation preview
SHM WITH NANO CEMENT BASED SENSORS
GUILLAUME NOISEUX-LAUZÉ AND
GEORGES AKHRAS
ROYAL MILITARY COLLEGE OF CANADA
1
BACKGROUND
STRUCTURAL HEALTH MONITORING OVERVIEW
NANO CARBON COMPOSITE OVERVIEW
OBJECTIVES
EXPERIMENTAL TESTS
SPECIMEN PREPARATION
TEST SETUP
RESULTS & DISCUSSION
ONGOING & FUTURE WORK
CONCLUSIONS
QUESTIONS
OUTLINE
2
BACKGROUND
Overarching research framework
The main objective of SHM is to :
Monitor the in-situ behaviour of a structure accurately and efficiently.
Detect damage and determine the condition of the structure.
The information can then be incorporated into management strategies.
STRUCTURAL HEALTH MONITORING OVERVIEW
3
BACKGROUND
Carbon Nanotube (CNT) & Carbon Nanofiber (CNF) Reinforced Cement-Based Composite can potentially address two SHM challenges:
Improve monitoring and sensing abilities by having the structural material itself act as a sensor.
Improve material durability by inducing ductility, toughness and control crack growth.
NANO CARBON REINFORCED COMPOSITE
4
BACKGROUND
HOW DOES IT WORK?
Self-sensing (piezoresistive) cement based material is made from cement mixed with electrically conductive fillers to increase it’s ability to sense the strain, stress while maintaining good mechanical properties.
NANO CARBON REINFORCED COMPOSITE
5
BACKGROUND
HOW DOES IT WORK? (cont’d)
As the piezoresistive cement based material is deformed or stressed, the contact between the fillers and the cement matrix is changed, which affects its electrical resistance.
Strain, stress, crack and damage can therefore be detected through measurement of the electrical resistance.
NANO CARBON REINFORCED COMPOSITE
6
BACKGROUND
Self-sensing pavement for traffic monitoring & vehicule loading measurements.
Smart highways that will potentially track the location, weight and speed of traffic.
In situ wireless and embedded sensors for damage detection in concrete structure.
APPLICATIONS
7
The primary objective is to look into the piezorisitivity capability of carbon nanotubes (CNT) and carbon nanofiber (CNF) reinforced cement-based material. The secondary objective is to look at the effect of the Nano additive on compressive strength.
OBJECTIVE & WORKPLAN
8
EXPERIMENTAL TEST
CEMENT PASTE MIX PROPORTION
Weight Cement Weight %
Cement 1308.2 Kg/m3 -
Water 524.3 Kg/m3 40.0%
Super Plast. 6.6 Kg/m3 0.5%
Silica Fume 65.7 Kg/m3 5.0%
CNT 0 - 2.62 Kg/m3 0 - 0.2%
CNF 0 - 2.62 Kg/m3 0 - 0.2%
Specimen
CNT CNF
(wt% Cement) (wt% Cement)
#1 0.1% CNF 0 0,1
#2 0.2% CNF 0 0,2
#3 0.1% CNT 0,1 0
#4 0.2% CNT 0,2 0
#5 Control 0 0
#6 0.1% CNF /0.1% CNT 0,1 0,1
#7 0.2% CNF /0.2% CNT 0,2 0,2
9
Multi-walled Carbon Nanotube (MWNT), Nanocyl™ NC 7000l.
Carbon nanofiber (CNF), Pyrograf®-III PR 24 XT-LHT,
EXPERIMENTAL TEST
SPECIMEN PREPARATION
PROPERTY UNIT VALUE
Average diameter nm 9.5
Average length microns 1.5
Surface area m2/g 250-300
Carbon purity % 90
PROPERTY UNIT VALUE
Average diameter nm 100
Average length microns 50-200
Surface area m2/g 43
10
Water+Superplasticizer+CNT/CNF.
Ultrasonic liquid processor (20 sec On 20 seconds Off) for 40 min.
Processing capacity of 1L.
EXPERIMENTAL TEST
SPECIMEN PREPARATION
11
Effect of superplasticiser on hydrophobic property of CNT.
EXPERIMENTAL TEST
SPECIMEN PREPARATION
12
Cement & silica fume mix in the Hobart mixer for 5 min.
The water/ CNT/ CNF solution was then added in the Hobart mixer and mixed for 5 min.
Cement paste was then poured in the cylinder mould (D=75mm, H=150mm) and lightly vibrated.
Strain gages were installed after approx. 30 days.
EXPERIMENTAL TEST
SPECIMEN PREPARATION
13
Resistivity measurement
Metal disks.
Carbon conductive grease.
EXPERIMENTAL TEST
EXPERIMENT SET-UP
14
Resistivity meter.
500 kN Test Frame.
HBM Data Acquisition.
EXPERIMENTAL TEST
EXPERIMENT SET-UP
15
Cyclic compressing test with amplitude ranging from 1-20 kN with a loading rate of 0.2 kN/sec was conducted.
Standard Test for Compressive Strength of Cylindrical Concrete Specimens were completed.
Specimens’ resistivity were recorded throughout the experiments.
EXPERIMENTAL TEST
EXPERIMENTS
16
EXPERIMENTAL TEST
EXPERIMENTS
17
EXPERIMENTAL TEST
RESULTS - CYCLIC COMPRESSING TEST
-6.00
-4.00
-2.00
0.00
2.00
4.00
6.00
-6.000
-4.000
-2.000
0.000
2.000
4.000
6.000
0 200 400 600 800 1000 1200 1400 FCR
(%
)
Stre
ss (
MP
a)
Time (sec)
0.1% CNF
Stress Fractional Change in Resistivity
18
EXPERIMENTAL TEST
RESULTS - CYCLIC COMPRESSING TEST
-22.00
-17.00
-12.00
-7.00
-2.00
3.00
8.00
13.00
18.00
-10.00
-8.00
-6.00
-4.00
-2.00
0.00
2.00
4.00
6.00
8.00
10.00
0 500 1000 1500 2000 2500 3000 FCR
(%
)
Stre
ss (
MP
a)
Time (sec)
0.1% CNT / 0.1% CNF
Stress (Mpa) FCR (%)
19
EXPERIMENTAL TEST
RESULTS - CYCLIC COMPRESSING TEST
FCR = 0.0114Ɛ + 1.05
-6.00
-5.00
-4.00
-3.00
-2.00
-1.00
0.00
1.00
-700 -600 -500 -400 -300 -200 -100 0
Frac
tio
nal
Ch
ange
in R
esis
tivi
ty (
FCR
)
Avg Strain (µm/m)
FCR /Strain
0-10kN loading
0-20 kN loading
20
EXPERIMENTAL TEST
0
50
100
150
200
250
300
350
400
Re
sist
ivit
y (O
hm
*m
)
Specimens Resistivity
Control
0.1% CNF
0.2% CNF
0.1% CNT
0.2% CNT
0.1% CNF /0.1% CNT
0.2% CNF /0.2% CNT
21
EXPERIMENTAL TEST
RESULTS - STANDARD COMPRESSIVE STRENGTH TEST
-16.00
-11.00
-6.00
-1.00
4.00
9.00
14.00
-60.00
-40.00
-20.00
0.00
20.00
40.00
60.00
0 100 200 300 400 500 600 FCR
(%
)
Stre
ss (
MP
a)
Time (sec)
0.1% CNT
Stress FCR
-16.00
-11.00
-6.00
-1.00
4.00
9.00
14.00
-80.00
-60.00
-40.00
-20.00
0.00
20.00
40.00
60.00
80.00
0 100 200 300 400 500 FCR
(%
)
Stre
ss (
MP
a)
Time (sec)
Control
Stress FCR
22
EXPERIMENTAL TEST
0
10
20
30
40
50
60
70
Control, Cement Paste
(CP)
0.1% CNF (CP) 0.2% CNF (CP) 0.1% CNT (CP) 0.2% CNT (CP) 0.1% CNF /0.1% CNT (CP)
0.2% CNF /0.2% CNT (CP)
Co
mp
ress
ive
Stre
ngt
h (
MP
a)
Compressive Strength of Cylindrical Cement Paste Specimens
23
EXPERIMENTAL TEST
CHALLENGES FOR DEVELOPMENT
Repeatable, large-scale and low energy method for distributing CNTs in cement-based materials.
Current fabrication procedures require a controlled environment only available in a lab.
Cost of CNTs & CNF (has fallen 100-fold since 1990 but still…).
Unknown long term durability and effect of environment.
24
ONGOING AND FUTURE WORK
The specimen in the second phase of testing contains aggregates with various concentrations of CNT and CNF.
These tests will help determine if the combination of CNT and CNF effectively overcomes challenges associated with the formation of conductive network in cement composite containing aggregates.
25
CONCLUSION
Results obtained during the first testing phase are coherent with other studies such as; Azhari et al. (2012) Tyson et al. (2011) and Han et al. (2010).
CNF/CNT-cement significantly increase the electrical conductivity vs CNT-cement or CNF-cement alone.
The electrical resistance of the specimen changed in tandem with the strain levels and could be use as a sensor.
A lot more test needs to be conducted to created reliable & accurate models (Strain/FCR).
26
ACKNOWLEDGMENTS
The authors would like to thank NSERC for its financial support .
27
QUESTIONS?
28
SHM OVERVIEW
SHM is typically achieved by the continuous and autonomous monitoring of key structural parameters by embedding, in strategic positions, sensors such as: Electric-resistance strain gauges
Optic sensors
Piezoelectric ceramic.
Most of these sensors have considerable shortcomings such as: Low sensitivity
High cost
Poor durability
Unfavourable compatibility with concrete structures. (i.e. loss of
structural mechanical properties)
Structurally ≈ ‘‘rolled-up’’ & “twisted” sheets of graphite
∅ ≈ 5-100 nm (hair ∅ is 25 μm 2500 -50 000 bigger)
Really high aspect ration (L/∅) > 1000 up to 1M (50 m hair)
Modulus of Elasticity can reach 1000 GPa (5 x steel)
The tensile strength up to 63 GPa (+50 x steel) (highest tensile strength of any material yet measured)
Large surface area (typically 200-300 m2/g)
CARBON NANOTUBE REINFORCED COMPOSITE
CNT STRUCRURE / PROPERTIES
Recommended