高雄應用科技大學學報 第三十五期 民國九十五年
Journal of National Kaohsiung University of Applied Sciences, Vol. 35 (2006), pp.309-316
Nondestructive Investigation of Cracks
in Concrete Pavement by Ultrasonic Pulse Velocity
Y. N. Sheen*
Abstract
A nondestructive testing, the ultrasonic pulse velocity method, is taken to evaluate the crack
depths and the quality of the concrete pavement in the runway at Magong airport in Taiwan. The
positions and length of the cracks from core specimens of the concrete pavement were measure,
and also apply the compressive loads to obtain the strength of the pavement. The construction
quality of concrete pavement is in an acceptable range if the pulse velocities are between 3571 and
4286 m/s here. The positions, the width and the length of the cracks measured directly from the
concrete cores are close to those estimated from the ultrasonic measurement. From test results, it
can be concluded that the ultrasonic pulse velocity method can be applied to evaluate the
damaged conditions of the concrete pavement.
Keyword：Nondestructive Testing, Ultrasonic Pulse Velocity, Cracks, Concrete Pavement
evaluation methods to monitor the structures in
1. Introduction
Recently the development of nondestructive
civil
engineering
are
similar
to
those
in
mechanical and aerospace fields. However, the
structures
made
from
concrete
are
evaluations (NDE) is rapid in civil engineering.
non-homogeneous and complicated due to the
Due to a great need of NDE, testing standards in
structural size and the materials. Therefore, the
many countries, for example ACI code, have
NDE method using in civil engineering needs to
included the evaluation technique of NDE.
modify depending on structure conditions.
Nondestructive evaluations in civil engineering
To assess the quality of concrete by NDE,
focus not only on the local area of structures but
one needs to investigate the strength, the flaws
also on a large area of construction site with
and the defects of concrete. There are many NDE
mapping the inspection results from a point to the
methods to evaluate concrete strength like the
area. For the purpose of long-term structure
rebound hammer method, the velocity testing
monitoring, the NDE method and the monitoring
method, the maturity test method, the pull-out
space had better consider in design[1,2,3].
testing method, the resistance method, and so on[4-7].
Nondestructive evaluations originated in the
To inspect the local defects of concrete, one can
demand of mechanical and aerospace fields. Most
use the ultrasonic method, the impact-echo
Received Auguset, 2005; revision received Dec., 2005; Accepted March, 2006.
*
Y. N. Sheen：Department of Clivid Engineering, National Kaohsiung University of Applied Sciences.
310
Y. N. Sheen
method, the shore-pulse radar method, the infrared
technique and the radiation method. This technical
2.2 T0 --Tc Method
paper will describe ultrasonic pulse velocity
This method is slight different from that in
method to evaluate the crack length of concrete in
BS-188 code. We first choose a distance on
airport pavement with case studies.
concrete with no existed cracks inside, and place
the transmitting transducer and the receiving
2. Crack Depth Calculations
transducer of the ultrasonic on the different side of
this distance, marking the distance referred as L.
The transmitting time of the longitudinal wave
2.1 BS-188 Code
between transducers is denoted as t0, and the
To measure the crack depth, let the
transmitter transducer and the receiver transducer
transmitting velocity of the ultrasonic in contact
concrete is
of the ultrasonic apart from a distance about
150mm on the concrete surface, where an existed
V
crack is between transducers. The transmitting
L
................................................... (3)
t0
time of the longitudinal wave within this distance
Then, we locate an existed crack, and mark
is denoted as t1. Again, the transmitter transducer
two points on the opposite sides of this crack on
and the receiver transducer of the ultrasonic are
concrete with a distance L/2. The transmitter
placed on the concrete surface with a 300mm
transducer and the receiver transducer of the
distance between them, and one measures the
ultrasonic are placed on the marked points to
transmitting time denoted as t2. Assuming that the
measure the transmitting time tc due to the
ultrasonic velocity V is the same through the
diffraction through the existed crack-tip. Assume
concrete, then
that the transmitting path of the pulse wave is
2 150 2  d 2
2 300 2  d 2
V

..... (1)
t1
t2
linear, the transmitting length S inside the
concrete from the transmitter transducer, through
the crack-tip, and to the receiver transducer is
where d = the length of the existed crack in
concrete. From (1), we obtain
d  150
4t12  t 22
t 22  t12
................................ (2)
S  V  t c  2 ( L / 2) 2  d 2 .................. (4)
where d = the crack depth. We can calculate
the crack depth inside the concrete from (4), or
the form
Once we know the transmitting time t1 and t2
between the transducers, the crack depth within
the concrete will be determined.
d
1 2 2
t c V  L2 ................................ (5)
2
Nondestructive Investigation of Cracks in Concrete Pavement by Ultrasonic Pulse Velocity
311
3. Measurement
3.1 Measured Positions
The concrete pavement located in the runway
of Magong airport, one of military airports in
Taiwan, was found some plastic cracks on its
Figure 2.
Specify the position of ultrasonic
transducers.
surface after some constructions, where the
bending strength of concrete is 45 MPa in design.
According to the damaged conditions, we chose
three locations with 40 investigation areas in this
airport totally by means of a nondestructive
evaluation and taking core specimens to assess the
crack depth of the concrete pavement.
3.2 Ultrasonic Pulse Velocity Measurement
Figure 3. Grind the surface to make it smooth.
For the nondestructive testing, the ultrasonic
digital equipment shown in Figure 1 was used to
calculate the crack depth of the concrete slabs in
the runway. The measured equipment, James V
Meter Mark II, belongs to an ultrasonic pulse
system.
The crack depth of the concrete pavement
can be determined by BS-188 code and T0 --Tc
method. The measured procedures are shown in
Figure 4. Put the coupling agent on the surface.
Figures 2-5.
Figure 1. Ultrasonic pulse velocity equipment.
Figure 5. Place the transmitting transducer and the
receiving transducer in positions.
312
Y. N. Sheen
velocity in S region. The variations of the
3.3 Core Observation
experimental data between the pulse velocity and
After using the ultrasonic pulse method to
the crack depth are large, and do not have a
estimate the crack depth of the concrete pavement,
regular rule. Most crack depths evaluated by
we took some core specimens, shown in Figure 6,
ultrasonic measurement in concrete pavement are
to measure the crack depth, and the distribution of
within a 36mm ~ 75mm range, it means that, the
the aggregate and the voids.
concrete quality in S region is of less serious
damage after the construction. However, there are
still 5 measured areas having the serious damages
due to the measured crack depth from 75mm to
225mm.
Table 1.
Crack Depth and Pulse Velocity in S
Region.
specimen No.
crack depth
(mm)
pulse velocity
(m/s)
S02-06
39
4167
S02-13
48
3947
S04-09
180
4054
S07-09
225
4225
S08-05-1
207
4000
S08-05-2
61
3947
According to the recorders of Magong
S10-03
60
3896
weather observation station, the temperature
S10-05
108
4110
between 8.9 oC and 22.1 oC during the ultrasonic
S10-06
144
4054
S11-06
216
4110
S12-04
40
3797
S12-06
139
4167
S13-06
67
4054
S15-07
36
3797
S16-04
75
4286
S17-04
40
4225
S18-04
57
4110
S22-01
71
4000
S22-02
43
3947
S29-03
55
3896
S30-04
65
4054
Figure 6. Measure the crack depth of core specimen.
4. Results and Discussion
4.1 Ultrasonic Measurements
measurement was suitable for the delivery of
pulse wave in concrete. The crack depth of the
concrete pavement can be evaluated by the
ultrasonic pulse velocity method, and calculated
from the pulse transmitting time between the
transducers. Those results for the crack depth and
the pulse velocity are shown in Tables 1-2, where
the specimen number is specified by the grid
depending on the measured positions in the airport
runway.
The results shown in Table 1 are the crack
depth of the concrete pavement and the pulse
Nondestructive Investigation of Cracks in Concrete Pavement by Ultrasonic Pulse Velocity
S31-05
48
313
3750
Table 2.
Crack depth and pulse velocity in C and J
regions.
specimen No.
crack depth
(mm)
pulse velocity
(m/s)
C02-02
73
3750
C04-02
54
3797
C04-03
70
3750
C04-04
64
3750
C04-05
92
3846
C06-06
69
4110
C07-11
48
3846
C08-07
53
3659
C08-10
--
4225
C08-12
--
4000
C09-14
66
3797
C10-04
149
3896
C10-06
233
3797
C10-21
70
3571
C11-21
29
4110
C12-21
--
3846
C13-16
--
5769
C14-13
66
4286
C15-11
54
4110
C16-08
86
4286
C16-09
28
4286
C17-06
--
2586
C17-07
--
4167
J07-01
194
3659
J09-01
145
3846
J10-01
74
3659
J10-05
205
3704
J12-01
210
3846
L04-20
221
3797
314
Y. N. Sheen
The results shown in Table 2 are the crack
*Unit: mm
depth and the pulse velocity in C and J regions.
The crack depths between 48 mm and 92mm
indicate less damaged conditions in the concrete
pavement, and those between 140mm and 221mm
show serious damaged ones.
From Table
1-2,
the
measured
pulse
velocities within the airport pavement here are
between 3571 m/s and 4286 m/s. This means that,
in this airport, the concrete quality in the
pavement after the construction is under control.
4.2 Core Measurements
We took core specimens from S08-05-2,
C10-03, C10-06, J07-01, J09-01 and J12-01 areas,
and measure the crack properties of those concrete
Figure 7. Description of the aggregate and the
crack in C10-06.
cores. The results for the crack properties of core
specimens are shown in Table 3, where the crack
depth measured by core specimen and by
ultrasonic are depicted in column 4 and column 5,
respectively.
Meanwhile,
four
of
six
core
specimens, C10-06, J07-01, J09-01 and J12-01,
show the split fracture by observing core
specimens.
From the results in Table 3, the crack depths
measured by core specimens in S08-05-02,
C10-06 and J12-01 areas are close to those by the
ultrasonic pulse method. Therefore, we can
directly describe the distribution of the aggregates
and the voids by pen in those three areas. The
description of the aggregate in the core specimen,
Table 3. Crack properties measured by core specimens.
such as C10-06 depicted in Figure 7, is pretty
uniform. Thereby, one can conclude that the crack
specimen
No.
width*
in surface
width*
in core
depth*
by core
depth*
by ultrasonic
S08-05-2
1.0
1.0
63
61
C10-03
0.5
1.0
57
149
The core specimens contain some voids with 2mm
C10-06
1.0
0.5
233
233
~ 5mm diameter.
J07-01
1.0
1.0
228
194
Besides, we are still unable to estimate the
J09-01
1.0
0.3
260
145
peak strength of the damaged concrete by
J12-01
0.5
1.0
210
210
comparing the ultrasonic measurements with core
depth of the airport pavement estimated by the
ultrasonic measurement is an acceptable method.
specimens ones.
Nondestructive Investigation of Cracks in Concrete Pavement by Ultrasonic Pulse Velocity
5. Conlusions
315
References
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by
ultrasonic
measurements are close to those by the
concrete
core
measurements
if
the
The
ultrasonic
pulse
measurement
for
Chinese
Corrosion
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of
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determining the crack depth of the concrete
pavement in the airport is an acceptable
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Pulse
Velocity
Device
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Techniques
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and
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Acknowledgments
The partial support of the National Kaohsiung
University under Grant 93A6027 is gratefully
acknowledged.
316
Y. N. Sheen