ST9302-SY011128ALPHA TESTING, INC.
2209 Wisconsin St., Suite 100
Dallas, Texas 75229
972/620-8911 - 972/263-4937 (Metro)
FAX: 972/406-8023
November 28, 2001
CITY OF COPPELL
255 Parkway Blvd.
Coppell, Texas 75019
Attention: Mr. Ken Griffin, P.E.
Final Report
NONDESTRUCTIVE TESTING FOR
MUD BALLS IN PAVEMENT
Sandy Lake Road Pavement
Coppell, Texas
ALPHA Report No. 00723-1
Attached is the report of the nondestructive testing for mud balls in pavement along a portion of
Sandy Lake Road. After you have had and opportunity to review, please call with any questions
you may have. If we can be of further assistance, please contact our office.
Sincerely yours,
President
JLH/pc
Copies: (2) Client
Geotechnical Engineering · Consfrucfion Materials Testing · Environmental Engineering · Consulting
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SANDY LAKE ROAD PAVEMENT
Nondestructive Testing for Mud Balls In Pavement
Coppell, Texas
Aldo Delahaza (J~.~-'
Project Engineer
D~)ugla~ W./Deno, P.E.
Senior Consultant and Project Manager
Final Report
27 November 2001
WJE No. 2000.3576.2
Prepared for:
Alpha Testing, Inc.
2209 Wisconsin Street, Suite 200
Dallas Texas 75229
Prepared by:
Wiss, Janney, Eistner Associates, Inc.
3050 Regent Boulevard, Suite 100
Irving, Texas 75063~3107
972.550.7777 tel I 972.373.9403 fax
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TABLE OF CONTENTS
!
]~troduction ..................................................................................................................................................
Background and Scope .................................................................................................................................
]_qYestigation ................................................................................................................................................. 1
Discussion .................................................................................................................................................... 3
Conclusions .................................................................................................................................................. 44
Recommendations ........................................................................................................................................
LIST OF FIGURES
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10a.
Figure 10b.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Figure 29.
Figure 30.
Figure 31.
Figure 32.
Westbound lanes of Sandy Lake Road exhibiting large surface voids ...................................... 6
Surface voids in Sandy Lake Road pavement ............................................................................ 6
Large and smaller surface voids in pavement ............................................................................ 7
Large surface voids in pavement ............................................................................................... 7
Test Panel 1; west of Nash Street .............................................................................................. 8
Test Panels 2 and 3; east of Holly Street ................................................................................... 9
Test Panel 4; east of Lodge Road ............................................................................................ 10
Test Panel 5; west of Trailwood Lane ..................................................................................... 11
Test Panel 6; west of Dobecka Drive ....................................................................................... 12
Schematic of Impact-Echo technique ...................................................................................... 13
Typical Impact-Echo frequency spectral plot .......................................................................... 13
Impact-Echo test in progress .................................................................................................... 14
Impact-Echo impactor/transducer ............................................................................................ 14
Ground-Penetrating Radar (GPR) in progress ......................................................................... 15
Data analyzer and LCD screen used with GPR technique ....................................................... 15
Grid marked on panels at 1 ft x 1 ft spacing ............................................................................ 16
Location of indication of internal flaw marked for subsequent core removal (Panel 4,
Core 16) ................................................................................................................................... 16
Panel 1; Panel located near STA 50+55 .................................................................................. 17
Panel 2; Panel next to the east side of Panel 3 ......................................................................... 18
Panel 3; Panel located approximately 51 ft. east of Holly Street ............................................. 19
Panel 4; Panel located between STA 43+50 and 44+00 .......................................................... 20
Panel 5; Panel located just west of STA 34+00 ....................................................................... 21
Panel 6; Panel located approximately 32 ft. west of STA 31+00 ............................................ 22
Coring operation ...................................................................................................................... 23
Four cores removed from pavement ........................................................................................ 23
Location of internal flaw indication (Panel 2, Core 15) .......................................................... 24
Core 15. Note mud ball at mid-depth of core .......................................................................... 24
Top portion of Core 10 in Panel 3 ........................................................................................... 25
Core hole at location of Core 10 in Panel 3 ............................................................................. 25
Location of Core 16 in Panel 4 ................................................................................................ 26
Close-up view of Core 16 in Panel 4. Concrete at surface was only about 1/2 to 1 in.
thick. There was only mud throughout remainder of pavement thickness .............................. 26
Core hole at Panel 3, Core 1 location. Note that mud ball extends into pavement
beyond the core hole ................................................................................................................ 27
Core hole at Panel 2, Core 5, a random core. No mud ball present at this location ................. 27
Sandy Lake Road Pavement Final Report: 27 November 2001
Nondestructive Testing for Mud Balls in Pavement Page i
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SANDY LAKE ROAD PAVEMENT
Nondestructive Testing for Mud Balls in Pavement
Coppell, Texas
INTRODUCTION
As requested, Wiss, Janney, Elstner Associates, Inc. has completed the authorized initial phase of
nondestructive testing at selected locations of the westbound lanes of Sandy Lake Road, Coppell, Texas.
The purpose of the initial phase of this proposed nondestructive testing program was to attempt to
determine if mud balls, not visible at the surface of the pavement, exist deeper within the pavement, and if
nondestructive testing (NDT) techniques are a viable method of detecting them.
BACKGROUND AND SCOPE
When extensive visible surface voids, Figures 1 through 4, were noted on the recently constructed
westbound lanes of Sandy Lake Road between MacArthur Boulevard and Denton Tap Road, a limited
coring program was conducted. The cores, taken at the locations of both large and small visible surface
voids, verified that the voids were due to large mud balls within the pavement concrete. In fact, at some
instances, the size of the mud ball was much larger than anticipated based on the size of the existing
visible surface voids. Due to this, there was concern as to whether more large mud balls, not visible at the
surface, were present in the pavement.
The detection of internal discontinuities in concrete is possible with various NDT techniques. For
slructural members, the use of Ultrasonic Pulse Velocity is commonplace when the concrete member can
be accessed from two sides. Pavements, where only one-sided access is possible, require a different
procedure, the Impact-Echo (IE) technique. When relatively small discontinuities are present, their
detection is more difficult and requires that the IE readings be made at a close spacing. In fact, it must be
noted that neither this method, nor any other that we are aware of, will reliably detect very small
subsurface mud balls.
We proposed that this work be performed in a phased manner, the initial phase being a trial program to
determine the reliability of the method and determine the required spacing of the impact readings. The
results would be used to determine the feasibility of a reliable test program. The work was to be limited to
a few selected panels in the westbound lanes, and was to be performed following construction of the
eastbound lanes.
INVESTIGATION
The initial test program was performed during the week of August 13-17, 2001, at six selected pavement
panels (between control joints and two lanes wide) in the westbound lanes, Figures 5 through 9. The
approximate locations, numbered sequentially from east to west, and the extent of visible surface voiding
were:
Panel 1 - Sixth panel west of Nash Street. "Good" panel with only a few small surface voids.
Panel 2 - Fourth panel east of Holly Street. "Bad" panel with many visible surface voids, some of
which are large.
Sandy Lake Road Pavement Final Report: 27 November 2001
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Panel 3 - Third panel east of Holly Street. "Bad" panel with many visible surface voids, some of
which are large.
Panel 4 - Sixth panel east of Lodge Road. "Moderate" panel with a few small surface voids and one
large surface void.
Panel 5 - Fourth panel west of Trailwood Lane. "Moderate" to "Poor" panel with several small to
medium surface voids and one large surface void.
Panel 6 - Seventh panel west of Dobecka Drive. "Good" panel with only a few small surface voids.
The proposed investigation was based on utilization of the Impact-Echo NDT technique.
The impact-echo testing is one nondestructive testing technique used to detect internal flaws within
concrete. This testing technique is also used to provide an indication of the in-sim quality of concrete as
well as to measure the thickness of concrete members.
The impact-echo method involves introducing a mechanical energy, in the form of a short pulse, into the
structure. A small diameter steel sphere (impactor) is used to generate the sound wave through the
pavement. A transducer mounted on the surface of the concrete receives energy reflections from
discontinuities, flaws or the bottom surface of the pavement. In essence, as the transmitted energy travels
through the material, changes in acoustic impedance in the material are detected, and the energy is
reflected back to the surface.
A schematic of the NDT set-up is attached as Figure 10a, and a typical signal pattern as Figure 10b.
Figures 11 and 12 show the equipment in use on Sandy Lake Road.
A second technique, ground penetrating radar, Figures 13 and 14, was also attempted, but it was
determined that the IE technique was more effective in this application.
At each test panel, a 1 fix 1 ft grid was marked on the pavement, Figure 15. However, due to time and
weather constraints, different grids were used on the various panels, some at the 1 ft x 1 ft grid, some at a
2 fix 2 ft alternating grid, etc. Also, in some locations, the entire panel was not tested.
As the NDT work progressed, locations of indicated intemal flaws were temporarily marked on the
pavement, Figure 16. At some locations where an internal flaw was indicated, a closer grid was used to
more precisely define the location and extent of the mud ball. Figures 17 through 22 are schematic plan
representations for the six panels illustrating the grid system and noting locations where internal flaws
were indicated.
As shown in the legends on Figures 17 through 22, the letter "G" is noted at the grid locations where no
internal flaw was indicated. An "F" was noted at the locations where an internal flaw was indicated, and a
"Q" was noted at grid locations where the test signal indicated a possible flaw.
Upon completion of the 1E tests, full depth cores were removed, Figure 23 and 24, by a coring company
retained by Alpha Testing, at several locations where the IE tests indicated an internal discontinuity and
from locations where no internal discontinuity was indicated. The core locations are indicated on
Figures 17 through 22 by the letter "C". The purpose of these cores was to calibrate the NDT equipment
and to verify the reliability of the test procedure. Additionally, WJE selected one random location in test
panels 1, 2, 4, 5, and 6 and removed a core at those locations. The purpose of the random cores was to
determine if mud balls could or would be located by random core removal.
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Figures 25 through 30 are views of various cores and core locations, illustrating some of the conditions
found to exist. Figures 28 and 31, at a core hole, illustrate that the mud balls were more extensive than
what is indicated by the cores; i.e., the mud balls extend into the pavement beyond the core holes. Figure
32 is the core hole where a random core was removed.
DISCUSSION
The Impact-Echo technique was successful in locating several mud balls that were not visible at the
pavement surface. In particular, the IE technique was useful for locating mud balls deep within the
pavement; i.e., three to four in. below the pavement surface. Eight cores were removed at locations where
flaws were indicated, and large mud balls were found at each of the eight locations.
At three "questionable" locations, no mud balls were noted on the core surface. Two of these (Cores 19
and 20 from Panel 5) were selected for vertical sectioning, and were cut into three vertical segments. One
of these had a small (1/2 to 3/8 in.) mud ball approximately 1/2 in. below the surface. Thus, it is possible
that questionable indications occur at small mud balls. A questionable indication might also occur if the
core location was slightly offset from a larger mud ball in the pavement. Two adjacent questionable
indications might occur if an internal flaw exists between the two grid locations.
At the seven coring locations selected where there was no indication of a below-surface anomaly, no mud
balls were noted on the core surfaces. Two of these were vertically sectioned, and no mud balls were
detected in the sections. Core 2 from Panel 3 was taken where there was a small visible surface void, but
surrounding tests indicated otherwise "good" concrete. Except for the surface void, the core surface did
not reveal any additional mud balls.
At the five randomly selected coring locations, no visible mud balls were noted on the core surfaces. Two
of these were selected for vertical sectioning, and no mud balls were noted in the sections.
Following is a table listing the panels, the number of test readings in each panel, and the number of
internal flaws detected:
Condition, Number of
Based on Primary Number of Number of Frequency:
Test Visible Test Internal Flaws Questionable Internal flaws per
Panel Surface Voids Locations Detected Flaw Indications X Test Locations
Panel 1 "Good" 228 0 2
Panel 2 "Bad" 247 4 1 1:62
Panel 3 "Bad" 469 7 12 1:70
Panel 4 "Moderate" 125 1 2 1:125
Panel 5 "Moderate" 63 0 5
Panel 6 "Good" 126 0 1
Although the frequency varies, the number of mud balls detected is quite large, especially in the panels
rated "bad" based on visible surface spalls/voids. The test results indicate that a significant number of
mud balls, not visible at the surface, exist within the pavement. Had a closer spacing been used for the test
readings, it is probable that more mud balls would have been detected.
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Where detected, most of the mud balls were quite large. At one location (Core 16 in Panel 4), the mud
ball started about 1/2 to 3/4 in. below the pavement surface and extended full depth for the entire diameter
of the core, Figures 29 and 30. There was no visible evidence of the existence of that mud ball at the
surface of the pavement.
CONCLUSIONS
From a technical point of view, the results of the NDT program were judged to be successful in that mud
balls, not visible at the surface, could be detected. The tests, and confirmation cores, show that many mud
balls exist within the pavement cross-section, some of which are very large. However, it is our opinion
that the use of this technique on a closely spaced testing interval, and other nondestructive techniques,
may not be cost-effective.
Five cores at randomly selected locations did not reveal the presence of mud balls, thus indicating that the
use of random coring locations is not a reliable method of detecting the presence of mud balls.
RECOMMENDATIONS
It is our opinion that performing Impact-Echo tests at the close interval necessary to detect all (or most) of
the significant subsurface mud balls in this length of pavement would be cost-prohibitive. A second
nondestructive technique, ground-penetrating radar, was also judged to not be an effective technique.
Thus, an alternative approach to this problem is suggested. A full length visual survey could be performed
and the results used to designate panels as "good", "moderate", or "bad". On the moderate and bad
panels, IE tests at a larger test grid spacing would be performed and the results used to develop a standard
on which a panel repair/replacement criterion could be based.
It is possible that significant mud balls near the surface could be detected by some form of infrared
equipment during certain times of the day, or during certain weather conditions. This procedure may also
be cost-prohibitive.
It is also our opinion that significant near-surface mud balls will eventually result in surface failure of the
pavement at those locations. A periodic visual survey would allow detection and documentation of such
occurrences.
The scope of our work did not include observations or testing of the eastbound lanes or various turning
lanes, ttowever, during initial main-line paving of the eastbound lanes a few months aRer completion of
the westbound lanes, we were requested to visit the project. At that time, we observed mud ball
contamination in the coarse aggregate stockpile at the concrete batch plant. Consequently, we suspect that
mud balls may also exist in some portions of the eastbound pavement lanes. Thus, at the least, it would be
prudent to conduct a detailed visual survey of the eastbound lanes to determine if any surface voids,
possibly attributable to mud ball contamination, are present.
G:~2000PROJX3576.2~INAL RPT 27 Nov 01
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FIGURES
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Figure 1. Westbound lanes of Sandy Lake Road exhibiting large surface voids.
Figure 2. Surface voids in Sandy Lake Road pavement.
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Figure 3. Large and smaller surface voids in pavement.
Figure 4. Large surface voids in pavement.
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Figure 5. Test Panel 1; west of Nash Street.
Sandy Lake Road Pavement
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Figure 6. Test Panels 2 and 3; east of Holly Street.
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Figure 7. Test Panel 4; east of Lodge Road.
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Figure 8. Test Panel 5; west of Trailwood Lane.
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/~FFT ANALYZER
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IMPACT ( -~)+~ ....
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Figure l Oa. Schematic of Impact-Echo technique.
8.7 KHz
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Frequency, KHz
Figure I Ob. Typical lmpact~Echo frequency spectral plot.
Sandy Lake Road Pavement Final Report: 27 November 2001
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Figure 11. Impact-Echo test in progress.
Figure 12. Impact-Echo impactor/transducer.
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Figure 13. Ground-Penetrating Radar (GPR) tn progress.
Figure 14. Data analyzer and LCD screen used with GPR technique.
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Figure 15. Grid marked on panels at 1 fix 1 fi spacing.
Figure 16. Location of indication of internal flaw marked for subsequent core
removal (Panel 4, Core 16).
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Figure 23. Coring operation.
Figure 24. Four cores removed from pavement.
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Figure 25. Location of internal flaw indication (Panel 2, Core 15).
Figure 26. Core 15. Note mud ball at mid-depth of core.
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Figure 27. Top portion of Core 10 in Panel 3.
Figure 28. Core hole at location of Core 10 in Panel 3.
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Figure 29. Location of Core 16 in Panel 4.
Figure 30. Close-up view of Core 16 in Panel 4. Concrete at surface was only
about 1/2 to 1 in. thick. There was only mud throughout remainder of pavement
thickness.
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Figure 31. Core hole at Panel 3, Core 1 location. Note that mud ball extends into
pavement beyond the core hole.
Figure 32. Core hole at Panel 2, Core 5, a random core. No mud ball present at
this location.
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