Stage 5 Distribution
January 2007
Research Report: UCPRC- RR- 2006- 10
Construction and Preliminary HVS Tests
of Pre- Cast Concrete Pavement Slabs
Authors:
E. Kohler, L. du Plessis, and H. Theyse
Work Conducted as part of Partnered Pavement Research Center Strategic
Plan Element No. 4.17: HVS testing of pre- cast PCC panels in District 8
PREPARED FOR:
California Department of Transportation
( Caltrans)
Division of Research and Innovation
PREPARED BY:
University of California
Pavement Research Center
UC Davis and Berkeley
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DOCUMENT RETRIEVAL PAGE RR No: UCPRC- RR- 2006- 10
Title: Construction and Preliminary HVS Tests of Pre- cast Concrete Pavement Slabs
Authors: Erwin Kohler, Louw du Plessis, and Hechter Theyse
Prepared for:
Caltrans Division of Research and
Innovation and Caltrans District 8
FHWA No:
CA081087B
Date:
January 2007
Strategic Plan Element No.:
4.17
Status:
Final
Version No:
Stage 5
Abstract:
This report presents the details on the construction and preliminary load tests on an experimental pavement comprised
of ten pre- cast slabs of the pavement known as the Super- Slab ® System, installed at the intersection of I- 15 and
SR210, in San Bernardino County in southern California. The construction of the test section consisted of: ( a)
Construction of a cement- treated base ( CTB), ( b) Preparation of a sand bedding layer, ( c) Placement of the pre- cast
slabs, ( d) Application of grout materials for the bedding and for the dowel/ tie bars, ( e) Diamond grinding the test pads,
( f) Filling the joints, and ( g) Construction of an asphalt concrete shoulder.
Subgrade evaluation was carried out with a dynamic cone penetrometer ( DCP) and indicated a strong granular
subgrade, with CBR ( California Bearing Ratio) between 45 and 80. Average backcalculated elastic modulus for the
CTB was about 2,200 MPa ( tested on the pre- cast panels) and presented great variation. Subgrade modulus was
70 MPa ( tested on CTB, consistent with results of testing on pre- cast panels). FWD testing showed deflections of 0.3 to
0.6 mm on the slabs, which after grouting were reduced to approximately 0.2 mm. The backcalculated elastic modulus
of the concrete was found to be between 19,000 and 23,500 MPa ( after grouting, averaging morning, and afternoon
FWD data). Load Transfer Efficiency ( LTE) values in the range of 5% to 40% were observed before grouting, and
consistently near 100% after grouting, revealing that the grouting process mobilized the dowel bars so that they
provided effective LTE. The materials used for the dowel grout and for the bedding grout showed flexural strengths at
28- days of 5.1 and 1.7 MPa, respectively.
The slabs were instrumented with displacement sensors ( vertical and horizontal) and with thermocouples. Thermal
deformations were collected, and revealed that the slab curl reduced from a range of ± 1.5 mm before grouting to ± 0.5
mm after grouting. The responses to traffic load also improved greatly after grouting. The wheel- induced deflections at
the transverse joint decreased to one- quarter of the initial value at the standard load of 60kN ( from about 1.0 mm to
0.25 mm). Rocking of the slabs, present before grouting, was also eliminated by grouting.
Two HVS tests were performed on the ungrouted slabs and indicated that the Super- Slab ® System is able to
withstand at least 86,500 ESALS in the ungrouted condition. This test was intended to simulate placement of the slabs
without grouting during one nighttime closure, and then grouting the slabs during the next nighttime closure 24 hours
later.
Keywords: Pre- cast concrete slabs, Super- Slab, Heavy Vehicle Simulator, HVS, Experimental pavement section,
Thermal Curling, Pavement Responses, Accelerated Pavement Testing, Instrumented Slabs
Proposals for implementation:
Overnight opening to traffic in the ungrouted condition is acceptable for the Super- Slab system
Related documents:
UCPRC- TP- 2005- 01: HVS Test Plan ( Strategic Plan Element 4.17), March 2005.
UCPRC- TM- 2007- 04: Interim Assessment of Expected Structural Life of Pre- Cast Concrete Pavement Slabs with HVS
Testing
Signatures:
E. Kohler
1st Author
J. Harvey
Technical Review
D. Spinner
Editor
J. Harvey
Principal
Investigator
M. Samadian
Caltrans Contract
Manager
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DISCLAIMER
The contents of this report reflect the views of the authors who are responsible for the facts
and accuracy of the data presented herein. The contents do not necessarily reflect the official views
or policies of the State of California or the Federal Highway Administration. This report does not
constitute a standard, specification, or regulation.
PROJECT OBJECTIVES
This project is responsive to the topics identified by Caltrans District 8 in its request to the
Caltrans Pavement Standards Team ( PST) for evaluation of the Super- Slab ® System:
• The short- term objective is to determine failure mechanisms of the Super- Slab ® panels and
to answer a constructability issue regarding opening to traffic in the ungrouted condition.
• The long- term objective is to provide information to Caltrans to help determine how the
performance of pre- cast panels compares to current Long- Life Pavement Rehabilitation
Strategy ( LLPRS) designs for jointed plain concrete pavements.
The project involves the evaluation of longitudinal and transverse joint behavior;
measurement of load transfer efficiency; observations of possible joint deterioration; measurement of
faulting, cracking, and settlement that may result from slab and cement- treated base ( CTB)
deterioration; estimation of expected service life of Super- Slab ® pavement based on HVS test
results; and comparison of Super- Slab ® performance ( expected service life) to HVS tests conducted
at cast- in place jointed plain concrete slabs ( SR14 at Palmdale).
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EXECUTIVE SUMMARY
The California Department of Transportation ( Caltrans) evaluated the use of the Super- Slab ®
System as a long- life rehabilitation strategy for concrete pavements using Heavy Vehicle Simulator
( HVS) tests on a specially constructed experimental pavement in San Bernardino County. The
Pavement Standards Team ( PST) technical lead for this project was the METS Office of Rigid
Pavements. The project originated in response to a request from Caltrans’ District 8.
This report describes the construction process of the test sections ( isolated arrangement of 5
by 2 slabs at the intersection of highways I- 15 and SR210) and presents the detailed results of the
preliminary short- duration performance tests.
Field Work Schedule
The overall schedule of the pavement construction and evaluation was:
• May 11, 2005 to June 8, 2005: Construction of test pavement, materials characterization,
HVS thermal curl tests, HVS ungrouted load tests. ( Documented in this report.)
• June 11, 2005 to September 20, 2005: HVS load test, dry condition, Section 597FD, ( first of
two sections).
• September 21, 2005 to February 24, 2006: HVS load test, dry condition, 598FD.
• February 24, 2006 to May 2, 2006: HVS load test, wet condition, 598FD.
• May 2, 2006 to August 30, 2006: HVS load test, wet condition, 597FD.
Construction
The construction of the Super- Slab ® System consists of three main activities: the
construction of the sand bedding layer, the precise placement of the pre- cast slabs, and the grouting
of the slabs. The main steps followed in the construction of the actual experimental section are:
• Construction of a cement- treated base ( CTB), The Super- Slab ® System will usually be
placed on an existing CTB that may be in a fairly advanced state of damage. In the case of
the HVS test sections, however, the pavement support was especially constructed.
• Preparation of a sand bedding layer. The function of the sand bedding layer is to provide an
even support to the pre- cast slabs, thereby eliminating as far as possible the formation of
voids between the pre- cast slabs and the support.
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• Placement of the pre- cast slabs. The pre- cast slabs are placed strictly according to a
predetermined grid. Although great care was exercised in preparing the bedding layer, the
edges of adjacent slabs did not align perfectly, resulting in surface irregularities at the joints
and corners.
• Application of grout materials for the bedding and for the dowel/ tie bars. The grouting system
consisted of a mechanical mixer with a piston pump and hoses with a customized fitting to
inject the grout through holes in the slabs. The grouting of the dowel and tie- bars was done
before the grouting of the bedding sand. A high- strength grout was used for the dowel and
tie- bars. The grout for the bedding material was of a lower strength and was of a more liquid
nature to ensure proper filling of any possible void between the slab and the support.
• Diamond grinding the test pads. Grinding of the surface to a level plane on the area of the
test sections to be wheel trafficked ( not the entire set of slabs, but just the loaded areas).
• Filling the joints. A backer rod was inserted into the joints, and a silicone seal was applied.
• Asphalt concrete shoulder. A temporary aggregate shoulder was replaced with an asphalt
concrete shoulder.
Material Characterization
Subgrade strength evaluation was carried out with a Dynamic Cone Penetrometer ( DCP),
and the results indicated a fairly stiff granular subgrade, with a California Bearing Ratio ( CBR)
between 45 and 80. Testing with a Falling Weight Deflectometer ( FWD) indicated deflections on the
CTB of approximately 0.8mm under 40kN loads. Backcalculated elastic moduli from the deflection
basins resulted on 200 to 600 MPa for the CTB while it was less than 14 days old and 50 to 100
MPa for the subgrade. FWD testing on the centers of the concrete slabs revealed maximum
deflections of 0.3 to 0.6 mm, which after grouting were reduced to approximately 0.2 mm. The
elastic modulus of the concrete was found to be between 19,000 and 23,500 MPa ( after grouting,
averaging morning and afternoon FWD data). The materials used for the dowel grout and for the
bedding grout were tested on beams to determine their flexural strengths ( modulus of rupture). At
28 days the results were 5.1 and 1.7 MPa, for the dowel and bedding grout, respectively ( dowel
grout being three times stronger than bedding grout).
Results of Preliminary Tests
The slabs were instrumented with displacement sensors and with thermocouples. Before
any load was applied to the pavement, deformations of the slab caused by temperature changes
were measured in the ungrouted and then in the grouted condition. This revealed that the slab’s curl
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at the corners was reduced from a range of ± 1.5 mm to a range of ± 0.5 mm by grouting the joints
and under the slabs. Load Transfer Efficiency ( LTE) values in the range of 5 to 40 percent were
observed at the ungrouted transverse joints, with and average of about 16 percent. LTE was
consistently close to 100 percent after grouting, revealing that the grouting process was effective in
mobilizing the dowels to provide excellent LTE at the joints. LTE was measured with the FWD and
with the sensors installed as part of the accelerated load testing with the HVS.
The responses to traffic load improved greatly after grouting. The deflections at the
transverse joint were reduced by the grouting to one- quarter of the ungrouted value ( from about 1.0
mm to 0.25 mm), meaning that the flexural stresses were also reduced. Rocking of the slab that
occurred under the HVS wheel loading before grouting was eliminated.
Two HVS tests were performed on the ungrouted slabs to simulate the exposure of the
ungrouted system to wheel loads. A total traffic of 86,500 ESALs was applied to each section over
about 32 hours of HVS loading on each one, using a wheel load of 60kN. The results of this part of
the experiment indicated that the Super- Slab ® System is able to withstand that level of traffic in the
ungrouted condition without observable or measurable damage.
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TABLE OF CONTENTS
Executive Summary........................................................................................................................ iv
List of Figures ............................................................................................................................... .. ix
List of Tables ............................................................................................................................... ... xv
Abbreviations Used in the Text..................................................................................................... xvi
1. INTRODUCTION................................................................................................................... ....... 1
2. CONSTRUCTION OF THE TEST SECTIONS.............................................................................. 5
2.1 Construction Process of the Super- Slab ® Test Grid................................................................ 5
2.1.1. Construction 7of the Sand Bedding Layer ........................................................................ 6
2.1.2. Placement of the Pre- Cast Slabs...................................................................................... 7
2.1.3. Grouting of the Slabs and Joints..................................................................................... 12
2.1.4. Joint Preparation and Grinding ....................................................................................... 14
2.2 Dynamic Cone Penetrometer Analysis ................................................................................. 14
2.3 FWD Surveys and Data Analysis .......................................................................................... 18
2.4 Laboratory Test Results........................................................................................................ 34
3. TEST SECTIONS NOMENCLATURE AND INSTRUMENTATION............................................ 37
3.1 Test Nomenclature................................................................................................................ 37
3.2 Instrumentation ..................................................................................................................... 38
4. TESTS PERFORMED BEFORE GROUTING ............................................................................ 42
4.1 Thermal Curl Test 597FDTC................................................................................................. 42
4.2 Ungrouted Load Tests Background ...................................................................................... 48
4.3 Load Test 597FDUG............................................................................................................. 49
4.3.1 Thermal Curl Response.................................................................................................. 51
4.3.2 Resilient Deflection Response ........................................................................................ 55
4.4 Load Test 598FDUG............................................................................................................. 70
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4.4.1 Thermal Curl Response.................................................................................................. 72
4.4.2 Resilient Deflection Response ........................................................................................ 77
5 TESTS PERFORMED AFTER GROUTING ............................................................................... 91
5.1 Thermal Curl Test 598FDTC................................................................................................. 91
5.2 Load Tests 597FD ................................................................................................................ 97
5.3 Load Tests 598FD .............................................................................................................. 100
6 PAVEMENT RESPONSES BEFORE AND AFTER GROUTING ............................................. 101
6.1 Comparison of Thermal Deformations ................................................................................ 101
6.2 Comparison of Load Responses......................................................................................... 103
7 CONCLUSIONS.................................................................................................................... ... 106
7.1 Subgrade and Base Construction, and Slab Placement ..................................................... 106
7.1.1 Subgrade Quality .......................................................................................................... 106
7.1.2 CTB quality ................................................................................................................... 106
7.1.3 Pre- Cast Panel Placement............................................................................................ 106
7.2 Effect of Grouting ................................................................................................................ 106
7.3 Opening to Traffic in Ungrouted Condition.......................................................................... 106
8 REFERENCES..................................................................................................................... .... 108
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LIST OF FIGURES
Figure 1. Location of the test sections at the interchange of highways I- 15 and State Route 210 in
San Bernardino County, CA.................................................................................................... 4
Figure 2. General area for the construction of the Super- Slab ® System test grid before construction. 5
Figure 3. Texture of the completed CTB prior to construction of the Super- Slab ® System................. 6
Figure 4. Construction of the sand bedding layer................................................................................ 7
Figure 5. Precise setting out of the corner locations of the pre- cast slabs. ......................................... 8
Figure 6. Details of the pre- cast slabs................................................................................................. 9
Figure 7. Placement of the pre- cast slabs........................................................................................... 9
Figure 8. Fixing the tie bars and placement of the slab on the adjacent lane.................................... 10
Figure 9. Spraying of the dowel bars with a bond- breaker. ............................................................... 10
Figure 10. Misalignment of adjacent slabs causing surface irregularities.......................................... 11
Figure 11. Final work on the joints between the ungrouted slabs...................................................... 11
Figure 12. Basic components of the grouting equipment. ................................................................. 12
Figure 13. The grouting of the dowel and tie- bar cavities.................................................................. 13
Figure 14. The grouting of the bedding material................................................................................ 13
Figure 15. Finishing details of the surface and joints. ....................................................................... 14
Figure 16. DCP positions at the Super- Slab ® test pavement area. ................................................... 15
Figure 17. DCP layer strength diagram for the test locations on the northern side of the site.......... 16
Figure 18. DCP layer strength diagram for the test locations on the southern side of the site. ........ 17
Figure 19. FWD survey rows on the base prior to Super- Slab ® placement. ...................................... 19
Figure 20. FWD data collected on the CTB layer. ............................................................................. 21
Figure 21. FWD test locations on each Super- Slab ® slab. ................................................................ 22
Figure 22. FWD data collection points on the concrete slabs............................................................ 22
Figure 23. Transverse joint LTE data from the corners of the slabs: Row A. ................................... 24
Figure 24. LTE data from mid- slab edge positions: Row A. ............................................................. 25
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Figure 25. Transverse joint LTE data from the corners of the slabs: Row C. ................................... 26
Figure 26. LTE data from the mid- slab edge positions: Row C. ....................................................... 27
Figure 27. FWD 40kN deflection data. .............................................................................................. 28
Figure 28. Backcalculated elastic moduli for the concrete, the cemented base, and the subgrade,
obtained from morning and afternoon deflection data........................................................... 30
Figure 29. Backcalculated stiffness of concrete layer. ...................................................................... 32
Figure 30. Backcalculated stiffness of CTB layer. ............................................................................. 33
Figure 31. Backcalculated stiffness of subgrade. .............................................................................. 34
Figure 32. Dowel grout modulus of rupture plotted against curing time. ........................................... 35
Figure 33. Bedding grout modulus of rupture plotted against curing time. ........................................ 36
Figure 34. Schematic of the positioning of the HVS and trafficked areas in tests 597FD
and 598FD. ........................................................................................................................... 37
Figure 35. Photographs of HVS2 during Tests 597FD and 598FD. .................................................. 38
Figure 36. Complete set of thermocouple and JDMD locations. ....................................................... 39
Figure 37. Trafficked test area and some JDMD anchors for Test 597FD. ....................................... 40
Figure 38. Examples of JDMDs and MDDs....................................................................................... 40
Figure 39. Photograph of JDMDs for Test 598FD. ............................................................................ 41
Figure 40. Thermocouples and JDMDs monitored during the thermal curl test on the ungrouted
slabs. ............................................................................................................................... .... 42
Figure 41. Average slab temperature during the ungrouted thermal curl test.................................... 43
Figure 42. Temperature gradient during the ungrouted thermal curl test. ......................................... 43
Figure 43. Adjusted vertical movement of the slab corners during the ungrouted thermal
curl test. ............................................................................................................................... 44
Figure 44. Adjusted horizontal joint activity during the ungrouted thermal curl test........................... 45
Figure 45. Example of the relationship between the temperature gradient and vertical movement of
the slab corners. ................................................................................................................... 45
Figure 46. The correlation between the temperature gradient and vertical movement of the slab
corners........................................................................................................................ ......... 46
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Figure 47. The correlation between temperature gradient and horizontal joint activity...................... 47
Figure 48. The correlation between the surface temperature and horizontal joint activity................. 47
Figure 49. Thermocouples and JDMDs monitored during the first ungrouted test, 597FDUG. ......... 49
Figure 50. Average slab temperature during the ungrouted test, 597FDUG. .................................... 50
Figure 51. Temperature gradient during the ungrouted test, 597FDUG............................................ 50
Figure 52. Adjusted thermal curl vertical position of the slab corners during the ungrouted load test,
597FDUG........................................................................................................................ ..... 51
Figure 53. Adjusted thermal curl horizontal joint activity during the ungrouted load test,
597FDUG........................................................................................................................ ..... 52
Figure 54. Adjusted thermal curl vertical position and temperature gradient for a shielded
slab corner during the ungrouted load test, 597FDUG.......................................................... 52
Figure 55. Adjusted thermal curl vertical position and temperature gradient for an exposed slab
corner during the ungrouted load test, 597FDUG. ................................................................ 53
Figure 56. Relationship between thermal curl and temperature gradient for the shielded slab
corners during the ungrouted load test, 597FDUG. .............................................................. 53
Figure 57. Relationship between thermal curl and temperature gradient for the exposed slab
corners during the ungrouted load test, 597FDUG. .............................................................. 54
Figure 58. Relationship between transverse joint horizontal deformation caused by thermal curl
activity and surface temperature during the ungrouted load test, 597FDUG. ....................... 54
Figure 59. Relationship between longitudinal joint horizontal deformation caused by thermal curl
activity and surface temperature during the ungrouted load test, 597FDUG. ....................... 55
Figure 60. Resilient vertical corner deflection influence lines for the first joint on the ungrouted load
test, 597FDUG...................................................................................................................... 56
Figure 61. Resilient vertical corner deflection influence lines for the second joint on the ungrouted
load test, 597FDUG. ............................................................................................................. 56
Figure 62. Resilient vertical corner deflection influence lines for the untrafficked side on the
ungrouted load test, 597FDUG. ............................................................................................ 57
Figure 63. Resilient vertical mid- slab deflection influence lines for the ungrouted load test,
597FDUG........................................................................................................................ ..... 58
Figure 64. Resilient shoulder joint activity influence lines for the ungrouted load test, 597FDUG..... 58
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Figure 65. Resilient longitudinal joint activity influence lines for the ungrouted load test, 597FDUG. 59
Figure 66. Resilient transverse joint activity horizontal deformation influence lines for the ungrouted
load test, 597FDUG. ............................................................................................................. 60
Figure 67. Formulation of the Load Transfer Efficiency..................................................................... 61
Figure 68. Peak approach slab and simultaneous leave slab deflection for the ungrouted load test,
597FDUG........................................................................................................................ ..... 62
Figure 69. Load Transfer Efficiency for the ungrouted test, 597FDUG. ............................................ 63
Figure 70. Transverse joint activity for the ungrouted load test, 597FDUG....................................... 65
Figure 71. Mid- slab deflection for the ungrouted test, 597FDUG. ..................................................... 65
Figure 72. Resilient vertical deflection of the shaded slab corners for the ungrouted test,
597FDUG........................................................................................................................ ..... 66
Figure 73. Resilient vertical deflection of the exposed slab corners for the ungrouted test, 597FDUG. 66
Figure 74. Resilient vertical deflection of the slab mid- slab edge for the ungrouted test. 597FDUG. 67
Figure 75. Resilient transverse joint activity for the ungrouted test, 597FDUG. ................................ 68
Figure 76. Resilient longitudinal joint activity for the ungrouted test, 597FDUG................................ 68
Figure 77. Thermocouples and JDMDs monitored during the second ungrouted test, 598FDUG..... 70
Figure 78. Average slab temperature during the ungrouted test, 598FDUG. .................................... 71
Figure 79. Temperature gradient during the ungrouted test, 598FDUG............................................ 71
Figure 80. Adjusted thermal curl vertical position of the slab corners during the ungrouted load test,
598FDUG........................................................................................................................ ..... 72
Figure 81. Adjusted thermal curl horizontal joint activity during the ungrouted load test, 598FDUG. 73
Figure 82. Adjusted thermal curl vertical position and temperature gradient for a shaded slab corner
during the ungrouted load test, 598FDUG. ........................................................................... 73
Figure 83. Adjusted thermal curl vertical position and temperature gradient for an exposed slab
corner during the ungrouted load test, 598FDUG. ................................................................ 74
Figure 84. Relationship between thermal curl and temperature gradient for the shaded slab corners
during the ungrouted load test, 598FDUG. ........................................................................... 74
Figure 85. Relationship between thermal curl and temperature gradient for the exposed slab corners
during the ungrouted load test, 598FDUG. ........................................................................... 75
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Figure 86. Relationship between transverse joint thermal curl activity and surface temperature during
the ungrouted load test, 598FDUG. ...................................................................................... 76
Figure 87. Relationship between longitudinal joint thermal curl activity and surface temperature
during the ungrouted load test, 598FDUG. ........................................................................... 76
Figure 88. Resilient vertical corner deflection influence lines for the first joint on the ungrouted load
test, 598FDUG...................................................................................................................... 77
Figure 89. Resilient vertical corner deflection influence lines for the second joint on the ungrouted
load test, 598FDUG. ............................................................................................................. 78
Figure 90. Resilient vertical corner deflection influence lines for the untrafficked joints on the
ungrouted load test, 598FDUG. ............................................................................................ 79
Figure 91. Resilient vertical mid- slab deflection influence lines for the ungrouted load test,
598FDUG........................................................................................................................ ..... 79
Figure 92. Resilient shoulder joint activity influence lines for the ungrouted load test, 598FDUG..... 80
Figure 93. Resilient longitudinal joint activity influence lines for the ungrouted load test, 598FDUG. 80
Figure 94. Resilient transverse joint activity influence lines for the ungrouted load test, 598FDUG.. 81
Figure 95. Peak approach slab and simultaneous leave slab deflection for the ungrouted load test,
598FDUG........................................................................................................................ ..... 82
Figure 96. Load Transfer Efficiency for the ungrouted test, 598FDUG. ............................................ 83
Figure 97. Transverse joint activity for the ungrouted load test, 598FDUG....................................... 84
Figure 98. Mid- slab deflection for the ungrouted test, 598FDUG. ..................................................... 85
Figure 99. Resilient vertical deflection of the shaded slab corners for the ungrouted test, 598FDUG. 86
Figure 100. Resilient vertical deflection of the exposed slab corners for the ungrouted test,
598FDUG........................................................................................................................ ..... 86
Figure 101. Resilient vertical deflection of the slab mid- slab edge for the ungrouted test, 598FDUG. 87
Figure 102. Resilient transverse joint horizontal deformation activity for the ungrouted test,
598FDUG........................................................................................................................ ..... 88
Figure 103. Resilient longitudinal joint horizontal deformation activity for the ungrouted test,
598FDUG........................................................................................................................ ..... 88
Figure 104. Part of a nontraffic- related tranvserse crack noticed on both sections after completion of
the ungrouted tests. .............................................................................................................. 90
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Figure 105. Thermocouples and JDMDs monitored during the thermal curl test on the grouted slabs. 91
Figure 106. Average slab temperature during the grouted thermal curl test...................................... 92
Figure 107. Temperature gradient during the grouted thermal curl test. ........................................... 92
Figure 108. Adjusted vertical movement of the slab corners during the grouted thermal curl test. .. 93
Figure 109. Adjusted horizontal joint activity during the grouted thermal curl test............................. 94
Figure 110. Example of the relationship between the temperature gradient and vertical movement of
the slab corners for the grouted slabs................................................................................... 94
Figure 111. The correlation between the temperature gradient and vertical movement of the slab
corners for the grouted slabs. ............................................................................................... 95
Figure 112. The correlation between the temperature gradient and horizontal joint activity for the
grouted slabs. ....................................................................................................................... 96
Figure 113. The correlation between the surface temperature and horizontal joint activity for the
grouted slabs. ....................................................................................................................... 96
Figure 114. Resilient vertical corner deflection influence lines for the west joint in Test 597FD ( after
grouting)...................................................................................................................... ......... 98
Figure 115. Resilient vertical mid- slab deflection influence lines in Test 597FD ( after grouting)....... 98
Figure 116. Resilient transverse joint activity influence lines in Test 597FD ( after grouting)............. 99
Figure 117. JDMD deflection and LTE summary for the west joint at 60 kN for the duration of test
597FD. ............................................................................................................................... .. 99
Figure 118. Initial JDMD deflection and LTE data for west joint at 60 kN plotted against the slab
temperature gradient........................................................................................................... 100
Figure 119. Comparison of the vertical deformations caused by thermal curl of the slabs before and
after grouting....................................................................................................................... 102
Figure 120. Comparison of the horizontal deformations caused by thermal activity of the slabs before
and after grouting................................................................................................................ 103
Figure 121. Typical vertical corner deflection influence lines from west joint in Test 597FD before
and after grouting................................................................................................................ 104
Figure 122. Typical JDMD data obtained at mid- slab in Test 597FD before and after grouting. ..... 104
Figure 123. Transverse joint activity change after grouting. ............................................................ 105
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LIST OF TABLES
Table 1: SI* ( Modern Metric) Conversion Factors ............................................................................ xvii
Table 2. Chronology of Construction and All Testing on Pre- Cast Panel Test Sections .................... 2
Table 3. Gradation of the Stone Sand Used in Bedding Layer............................................................ 7
Table 4. Summary of the Subgrade DCP Results ............................................................................. 17
Table 5. Backcalculated Moduli from Deflections Measured on Top of CTB..................................... 20
Table 6. Measured Load Transfer Efficiency Before and After Grouting, Morning and Afternoon.... 23
Table 7. FWD Deflections Measured at Slab Centers on Top of Pre- Cast Slabs.............................. 29
Table 8. Backcalculated Moduli from Deflections Measured on Top of Pre- Cast Slabs.................... 31
Table 9. Detailed results of Backcalculation from Deflections Measured on Top of
Pre— Cast Slabs ................................................................................................................... 31
Table 10. Modulus of Rupture ( MPa) Results for the Dowel and Bedding Grout .............................. 35
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ABBREVIATIONS USED IN THE TEXT
Average Daily Truck Traffic ( ADTT)
California Department of Transportation ( Caltrans)
Cement- treated base ( CTB)
California Bearing Ratio ( CBR)
Data Acquisition System ( DAS)
Dynamic Cone Penetrometer ( DCP)
Equivalent Single Axle Load ( ESAL)
Falling Weight Deflectometer ( FWD)
Heavy Vehicle Simulator ( HVS)
Joint deflection measurement devices ( JDMD)
Load Transfer Efficiency ( LTE)
Long- Life Pavement Rehabilitation Strategies ( LLPRS)
Layer Strength Diagram ( LSD)
Multi- depth Deflectometer ( MDD)
Partnered Pavement Research Center ( PPRC)
Portland cement concrete ( PCC)
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Table 1: SI* ( Modern Metric) Conversion Factors
APPROXIMATE CONVERSIONS TO SI UNITS
Symbol Convert From Multiply By Convert To Symbol
LENGTH
in inches 25.4 millimeters mm
ft feet 0.305 meters m
AREA
in2 square inches 645.2 square millimeters mm2
ft2 square feet 0.093 square meters m2
VOLUME
ft3 cubic feet 0.028 cubic meters m3
MASS
lb pounds 0.454 kilograms kg
TEMPERATURE ( exact degrees)
° F Fahrenheit 5 ( F- 32)/ 9 Celsius C
or ( F- 32)/ 1.8
FORCE and PRESSURE or STRESS
lbf poundforce 4.45 newtons N
lbf/ in2 poundforce/ square inch 6.89 kilopascals kPa
APPROXIMATE CONVERSIONS FROM SI UNITS
Symbol Convert From Multiply By Convert To Symbol
LENGTH
mm millimeters 0.039 inches in
m meters 3.28 feet ft
AREA
mm2 square millimeters 0.0016 square inches in2
m2 square meters 10.764 square feet ft2
VOLUME
m3 cubic meters 35.314 cubic feet ft3
MASS
kg kilograms 2.202 pounds lb
TEMPERATURE ( exact degrees)
C Celsius 1.8C+ 32 Fahrenheit F
FORCE and PRESSURE or STRESS
N newtons 0.225 poundforce lbf
kPa kilopascals 0.145
poundforce/ square
inch lbf/ in2
* SI is the symbol for the International System of Units. Appropriate rounding should be made to
comply with Section 4 of ASTM E380. ( Revised March 2003)
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1. INTRODUCTION
The California Department of Transportation ( Caltrans) evaluated the use of the Super- Slab ®
System ( Super- Slab ® ) as a long- life rehabilitation strategy for concrete pavements. A document
previously prepared by the University of California Pavement Research Center ( UCPRC) ( 1) outlines
the evaluation strategy proposed by Caltrans District 8 to assess suitability of the pre- cast slab
system. Besides the test plan, that document includes brief overviews of Caltrans’ Long- Life
Pavement Rehabilitation Strategies ( LLPRS) and of the Super- Slab ® System.
The District’s draft Evaluation Plan identified four objectives in its pilot program. The first
three objectives focus on evaluation of a trial project. They were to evaluate ( 1) design and contract
preparation requirements, ( 2) biddability of the Super- Slab ® Pavement pay item, and ( 3)
constructability. The fourth objective includes Heavy Vehicle Simulator ( HVS) testing to evaluate the
long- term performance of the Super- Slab ® System.
In January 2005, in response to the request from District 8, the Caltrans Pavement
Standards Team ( PST) asked the Division of Research and Innovation ( DRI) to direct the UCPRC to
perform HVS testing and associated testing and analysis on a test section with Super- Slab ®
Pavement pre- cast panels through the Partnered Pavement Research Center ( PPRC) contract
managed by DRI. The PST technical lead for this project was the METS Office of Rigid Pavements.
The scope of work included the following1:
1. Construction of test sections by the manufacturer.
2. Characterization of the pavement structure and materials.
3. Preliminary, short duration HVS testing of the pre- cast slab system, under the
following conditions:
a. HVS testing of the slabs previous to the grouting ( dowel bar slots in the joints and
bedding grout under the slab) to evaluate staged construction. The thinking is
that during a night closure some slabs would be placed in one closure and
opened to traffic with the joints ungrouted, followed by grouting of the joints in
another closure. The plan called for this testing to be performed without addition
of water to the pavement.
1 Construction ( item 1), material characterization ( item 2), and preliminary HVS testing ( item 3a) are the subjects of
this report. They were communicated to Caltrans in a provisional document submitted in August 2005 under title
“ Interim Report. HVS Testing of Super- Slab ® at the Junction of Highways I- 15 and SR210.”
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b. HVS testing of the slabs after grouting, in the dry condition and including the
application of very high loads to provide early results after a short duration of
testing.
c. HVS testing of the slabs under dry and wet conditions using a less aggressive
loading schedule to evaluate longer- term performance2.
The overall schedule of the construction of the test sections, and testing performed on them
is shown in Table 2.
Table 2. Chronology of Construction and All Testing on Pre- Cast Panel Test Sections
Date Operation Document in Which
Results are Presented
May 11, 2005 Construction of underlying
structure
May 20, 2005 FWD testing on underlying
structure
May 24, 2005 Placement of pre- cast slabs
May 25 and 31, 2005 FWD testing on slabs, ungrouted
May 27 and 28, 2005 Thermal curl test on 597FDUG
May 29 and 30, 2005 Load test on 597FDUG
May 30 and 31, 2005 Load test on 598FDUG
June 3, 2005 FWD testing on slabs, after
grouting
June 7 and June 8, 2005 Thermal curl test 598FDTC
This report
June 11 to September 20,
2005
HVS load test, dry condition,
597FD
Tech Memo Reference ( 2)
and
Research Report Reference
( 3)
September 21, 2005 to
February 24, 2006
HVS load test, dry condition,
598FD
February 24 to May 2, 2006 HVS load test, wet condition,
598FD
May 8, 2006 FWD testing at 598FD
May 2 to August 30, 2006 HVS load test, wet condition,
597FD
Research Report Reference
( 3)
This report describes the construction process of the test sections and presents detailed
results of the preliminary short- duration performance tests originally summarized in Reference ( 2).
These tests were performed on two HVS test sections, numbered 597 and 598 in the PPRC HVS
database, under ungrouted and grouted conditions. The results included in this report, as well as
those included in references ( 2) and ( 3), are indicated in Table 2.
2 Results of longer- term tests ( item 4) have been communicated to Caltrans through presentations, and will be
formally documented in a detailed report currently being prepared ( 3).
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The HVS test sections were constructed at the interchange of Interstate I- 15 and State Route
( SR) 210 in San Bernardino County. The location of the test section is presented in Figure 1.
The test results presented in this document include:
• Thermal curl tests performed on the slabs before grouting of the slabs and joints;
• Load tests on the slabs before grouting of the joints and slabs;
• Thermal curl tests after grouting of the joints and slabs; and
• Initial load tests on Section 597FD slabs after grouting of the slabs and joints to provide
preliminary results to the District. ( Longer- duration load tests performed afterward are
documented in Reference [ 3]).
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( a) State level ( b) Intersection level
( a) City level
Figure 1. Location of the test sections at the interchange of highways I- 15 and State Route
210 in San Bernardino County, CA.
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2. CONSTRUCTION OF THE TEST SECTIONS
This chapter provides an overview of the process followed during the construction of the
HVS test sections, including:
• Construction of the ten test slabs, arranged in a two- by- five slab grid;
• Analysis of the subgrade prior to construction of the cemented- base layer using Dynamic
Cone Penetrometer ( DCP) data;
• Structural evaluation of the Super- Slab ® System using Falling Weight Deflectometer ( FWD)
data measured after construction and prior to HVS loading; and
• Analysis of laboratory data from the concrete used during the manufacture of the concrete
slabs.
2.1 Construction Process of the Super- Slab ® Test Grid
The Super- Slab ® System is intended as a rapid replacement option for damaged concrete
pavements. Individual slabs or a whole section of the pavement may be replaced by the Super-
Slab ® System. This implies that the Super- Slab ® System will usually be placed on an existing
cement- treated base ( CTB) that may be in a fairly advanced state of damage. In the case of the
HVS test sections, however, the underlying pavement structure had to be built because the test
sections were not constructed on an existing, damaged pavement. The construction process
therefore started with the preparation of the subgrade and the construction of a CTB in the general
area shown in Figure 2. The thickness of the CTB was 4 inches, and its surface was relatively
uneven ( see Figure 3).
Figure 2. General area for the construction of the
Super- Slab ® System test grid before construction.
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Figure 3. Texture of the completed CTB prior to construction
of the Super- Slab ® System.
Construction of the Super- Slab ® System consists of four main steps:
1. Construction of the sand bedding layer,
2. Placement of the pre- cast slabs,
3. Grouting of the slabs and joints, and
4. Joint preparation and grinding.
2.1.1. Construction of the Sand Bedding Layer
The function of the sand bedding layer is to provide very even support to the precast slabs
thereby eliminating the formation of voids between the slabs and support to the maximum extent
possible. After spreading the sand on top of the CTB, the sand is wetted, compacted, and bladed
repeatedly to very tight profile tolerances. Figure 4 shows the compaction and blading of the sand
with a hand- propelled grader running on two rails to ensure an even surface. The thickness of the
bedding layer varied from about 6 mm to as much as 18 mm in spots since the surface of the CTB
was not even. The average thickness was 9 to 10 mm. The material used was stone sand with the
gradation indicated in Table 3. Fineness modulus was 2.84.
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Table 3. Gradation of the Stone Sand Used in Bedding Layer
Sieve No. Sieve Size
( mm)
Percent Passing
by Weight
3/ 8 9.5 100.0
4 4.75 98.4
8 2.36 80.7
16 1.18 63.9
30 0.600 46.2
50 0.600 20.7
100 0.150 6.6
200 0.075 0.0
( a) Compaction of the sand
bedding layer.
( b) Precision blading of the
sand bedding layer.
Figure 4. Construction of the sand bedding layer.
2.1.2. Placement of the Pre- Cast Slabs
After completion of the construction of the sand bedding layer, the exact corner locations of
the slabs are marked on the surface of the sand. The pre- cast slabs are placed strictly according to
this predetermined grid and not with a constant gap width. This is done to prevent creep of the slabs
which could result in the last of the pre- cast slabs butting up against an existing slab when a section
of pavement is replaced. Figure 5 shows the markings for the placement of the pre- cast slabs.
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Figure 5. Precise setting out of the corner locations of the pre- cast slabs.
Figure 6 shows certain details of the pre- cast slabs. Figure 6( a) shows the epoxy- coated
dowel bars cast into one end of the 4.572 m ( 15 ft) long by 3.962 m ( 13 ft) wide by 220 mm ( 9 in.)
thick slabs at the time of manufacture. Figure 6( b) shows the dove- tailed recesses on one of the
transverse edges of the slab that accept the dowel bars on the opposing end of the adjacent slab,
the foam strip on the longitudinal edge of the slab that confines the bedding grout, and the bedding
grout channel that runs underneath the slab. Figure 6( c) shows the female end of the tie bars cast
into the longitudinal edge of the slab that accepts the male ends of the tie bars as shown in Figure
6( d).
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( a) Epoxy- coated dowel bars cast into
the transverse edge of the slabs.
( b) Dowel- bar recesses and bedding
grout confinement strip.
( c) Female end of the tie- bars cast into
the longitudinal edge of the slab.
( d) Male- to- female connection
of the tie- bars.
Figure 6. Details of the pre- cast slabs.
The pre- cast slabs arrived on site on flat- bed trucks and were lifted and lowered into place
with a crane as shown in Figure 7. The tie bars were then screwed into the longitudinal edge of the
slab connecting to the adjacent lane and the adjacent slab placed as shown in Figure 8.
( a) Lifting of the slab from the flat- bed. ( b) Precise placement of the slab.
Figure 7. Placement of the pre- cast slabs.
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( a) Fixing the tie bars on
the longitudinal edge.
( b) Placement of the slab
on the adjacent lane.
Figure 8. Fixing the tie bars and placement of the slab on the adjacent lane.
The dowel bars and the transverse joint were then sprayed with a bond- breaker as shown in
Figure 9 and the placement of the slabs continued. Although great care was exercised in preparing
the bedding layer, the edges of adjacent slabs did not have perfect vertical alignment, resulting in
surface irregularities at the joints and corners as shown in Figure 10.
Figure 9. Spraying of the dowel bars with a bond- breaker.
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Figure 10. Misalignment of adjacent slabs causing surface irregularities.
Once all the slabs of the HVS test sections were in place, plastic spacers were driven into
the joints between the ungrouted slabs to prevent their movement, and the outer edges of the joints
were sealed using expanding foam to prevent ingress of material into the joint ( as shown in Figure
11). Figure 11( a) also clearly shows the grout holes for the dowel bars on the transverse joint and
the tie bars on the longitudinal joint. The construction team then continued with the construction of a
temporary aggregate shoulder around the perimeter of the five- by- two grid of pre- cast slabs.
( a) Plastic spacers being driven into the
joints between the ungrouted slabs.
( b) Expanding foam used for sealing of the
outer edges of the joints to prevent ingress
of material into the joint.
Figure 11. Final work on the joints between the ungrouted slabs.
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2.1.3. Grouting of the Slabs and Joints
On a normal replacement project, the ungrouted slabs would be exposed to traffic for a day
before the grouting continued during the next nighttime closure. The ungrouted slabs were therefore
instrumented and tested with the HVS before grouting continued. ( The details of the instrumentation
and testing are presented in Section 3.2.) After completion of the ungrouted tests, the grouting of
the slabs continued.
The fast- setting grout used in the grouting process required that the mix water be cooled
before mixing. Ice blocks were placed in the mix water to cool it. The grouting system consisted of a
mechanical mixer with a piston pump and hoses with customized fittings to inject the grout into the
grout holes in the slabs as shown in Figure 12.
( a) Mechanical mixer and piston pump. ( b) Hose with fitting for injecting
the grout.
Figure 12. Basic components of the grouting equipment.
The grouting of the dowels and tie bars at the joints was completed before the grouting of the
bedding sand. A high- strength grout was used for the dowels and tie bars. The injection fitting was
placed into one of the grout holes and the grout was pumped into the cavity until it started to flow
from the hole on the other end of the dowel and tie- bar cavities, as shown in Figure 13. The excess
grout was scraped off before it set.
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( a) Filling of the dowel and
tie- bar cavities with grout.
( b) Removal of excess grout.
Figure 13. The grouting of the dowel and tie- bar cavities.
Once the grouting of the dowel and tie- bar cavities was completed, the grouting of the
bedding material commenced. The grout for the bedding material was of a lower strength than the
grout used for the dowel and tie- bar cavities and was more like a fluid than a paste to ensure proper
filling of any possible void between the slab and the support. The bedding grout was applied in a
manner similar to the dowel and tie- bar grout but with the addition of a fitting placed in the exit hole
of the bedding grout, as shown in Figure 14.
( a) Injection of the bedding grout. ( b) Excess bedding grout pouring
from the exit hole.
Figure 14. The grouting of the bedding material.
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2.1.4. Joint Preparation and Grinding
The construction process was concluded by cutting of the joints to a constant width, grinding
of the surface to a level plane, filling the joints with a joint backer as shown in Figure 15, and sealing
the joints. The construction team then continued with removal of the temporary aggregate shoulder
and its replacement with an asphalt concrete shoulder.
( a) Level grinding of the surface. ( b) High- density foam strip
installed in the joints.
Figure 15. Finishing details of the surface and joints.
2.2 Dynamic Cone Penetrometer Analysis
The DCP is used to evaluate the structural strength of the unbound layers in a pavement
system through the measurement of the shear resistance of a standard cone pushed vertically into
the pavement under the influence of a standard falling weight ( 4, 5).
The field DCP data collection took place on May 6, 2005, on the undisturbed in situ soil
before the removal of any vegetation or subgrade preparation. A testing area 22.9- m long and 7.3- m
wide ( 74 ft by 24 ft) was identified as the area where the Super- Slab ® test pavement would be
constructed. In order to characterize the structural strength of the subgrade in this area, eight DCP
tests were done on the in situ soil at the locations indicated in Figure 16. Four DCP tests ( 4.6 m
apart) were done in two rows, 7.3 m apart for a total of eight DCP measurements. The first row was
toward the northern end of the testing area with holes marked 2N, 4N, 6N, and 8 N. The holes on
the southern end were marked 1S, 3S, 5S, and 7S.
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N
# 2 N # 4 N # 6 N # 8 N
7.3 m 2.7m
# 1 S # 3 S # 5 S # 7 S
4.5 m
22.8m
Figure 16. DCP positions at the Super- Slab ® test pavement area.
The subgrade at the location of the HVS test site consists of a sandy material with a fair
amount of stones embedded in the soil. These stones made penetration with the DCP very difficult
and only three of the eight DCP tests could be completed with the rod penetrating to the its full
length of 800 mm ( 2.6 ft). Five of the eight tests were stopped early because of very low or zero
penetration even after successive blows with the hammer.
Figure 17 shows the DCP layer strength diagram ( LSD) for the combined data of the DCP
tests done on the northern side of the test site. Although the DCP did not always penetrate to the
full depth of 800 mm the LSD clearly show that the top 200 mm ( 0.65 ft) of the subgrade generally
had a relatively high penetration rate of approximately 30 mm/ blow ( 0.1 ft/ blow). Below 200 mm
depth, the penetration rate decreased to between 2 and 4 mm/ blow ( 0.0065 and 0.013 ft/ blow) which
is very low for a pavement subgrade. These low penetration rates, combined with the fact that the
DCP did not always penetrate 800 mm, indicate a stony subgrade.
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DCP Layer Strength Diagram
0
100
200
300
400
500
600
700
800
1 10 100
Penetration rate, DN ( mm/ blow)
Depth ( mm)
Figure 17. DCP layer strength diagram for the test
locations on the northern side of the site.
Figure 18 shows the LSD for the combined data of the DCP tests done on the southern side
of the test site. Although the thickness of the top layer with the high penetration rate is only about
half of the thickness of this layer on the northern side, the general trend in the data is very similar to
the trend observed on the northern side of the site.
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DCP Layer Strength Diagram
0
100
200
300
400
500
600
700
800
1 10 100
Penetration rate, DN ( mm/ blow)
Depth ( mm)
Figure 18. DCP layer strength diagram for the test
locations on the southern side of the site.
Table 4 summarizes the DCP results. The table shows the number of blows to penetrate to
maximum depth, the average penetration rates in mm/ blow calculated for the upper portion of the
subgrade [ about 100 mm ( 0.32 ft) for the test locations on the southern side and 200 mm ( 0.64 ft) for
those on the northern side] as well as the average penetration rate for the portion of the subgrade
below the upper layer to the maximum depth of penetration.
Table 4. Summary of the Subgrade DCP Results
DCP Test Penetration Rate ( mm/ blow)
Location
Maximum
Penetration
Depth ( mm)
Number of Blows
to Maximum
Penetration Depth
Upper Portion Lower Portion
1 S 840 200 22 3.7
3 S 410 75 24 4.1
5 S 380 85 20 3.5
7 S 220 55 18 2.4
2 N 500 125 19 2.7
4 N 530 110 20 4.1
6 N 770 200 20 3.0
8 N 840 200 20 3.4
Average 20.4 3.3
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The results displayed in Table 4 are indicative of a fairly strong subgrade for the portion of
the subgrade below the upper layer. Penetration rates of below 6 mm/ blow are indicative of layers
consisting of good quality natural gravel often used as subbase material. Using well- established
correlations ( 2, 5) the in- situ CBR of the subgrade calculated using through the DCP data is between
45 and 80 which is significantly higher than the norm for subgrades, and indicates a granular
material.
Based on the results obtained by the DCP analysis it is concluded that the subgrade at the
site where the Super- Slab ® test section was constructed has sufficient bearing capacity to carry the
expected loads. If well protected through the design of a proper upper structure, the subgrade at
this testing area should not be the cause of any early unexpected failures under the influence of
repetitive loading.
It should be borne in mind that the presence of stones embedded in the subgrade has a
significant influence on the DCP results and all conclusions based on DCP data should be handled
with caution.
2.3 FWD Surveys and Data Analysis
Falling Weight Deflectometer tests ( FWD) were conducted at the test site:
• To determine the structural strength of the substructure ( base and subgrade). This was done
through FWD testing on the cement- treated base ( CTB) prior to the placement of the
concrete slabs;
• To assess the integrity of the joints before and after grouting was done based on the Load
Transfer Efficiency ( LTE) at the joints;
• To investigate the effects of temperature on LTE through a comparison between FWD data
collection during the hottest part of the day and data collected during the night;
• To determine the stiffness of the various layers of the complete structure, including the
concrete slabs.
To achieve this, a Heavy Weight Deflectometer ( HWD) was used. This equipment is
essentially the same as an FWD but with the capability for heavier loads than standard FWDs. The
HWD is normally used for the evaluation of strong concrete pavements such as airfields and was
used at the test site. For clarity the acronym “ FWD” will be used throughout this report although the
data was collected with an HWD.
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FWD surveys were done early in the morning, before sunrise, at low surface temperatures
and were repeated in the afternoons when the surface temperature was hotter. FWD testing was
performed at four stages of construction:
1. On May 20, 2005, on top of the cement- treated base;
2. On May 25, 2005, on the ungrouted slabs before the arrival of the HVS;
3. On May 31, 2005, on the ungrouted slabs not obscured by the HVS after the arrival
of the HVS; and
4. On June 3, 2005, after all concrete joints had been grouted, and prior to the start of
HVS testing.
FWD testing on the CTB prior to the placement of the Super- Slab ® test grid was done as
detailed in Figure 19. Row A is the southern side with Station 0 toward the western end of the
testing slabs, and with stationing increasing eastward.
Concrete slab posistions
N
Row C
7.3 m Row B
Row A
22.8m
Figure 19. FWD survey rows on the base prior to Super- Slab ® placement.
Figure 20 shows the FWD deflection data collected on the CTB prior to the placement of the
concrete slabs. The figure shows three graphs: the first is the FWD deflections normalized for a
40kN load, the second graph shows the backcalculated stiffness values of the CTB layer, and the
last graph shows the backcalculated stiffness values of the subgrade.
Although the deflections seem high [ on the order of 0.8 mm ( 2,000 mils)] it should be borne
in mind that the results were obtained with the FWD placed directly on top of the CTB layer.
The backcalculated stiffness values for the CTB typically ranged between 200 and 600 MPa
( 29,000 and 87,000 psi) and are somewhat lower than what would be expected from a newly
Station 0
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constructed layer without exposure to any traffic. The FWD survey on the CTB was done on May
20, 2005, while the DCP tests on the subgrade were done on May 6, 2005. The CTB had been
constructed less than 14 days prior to FWD testing and would not yet have reached maximum
strength. The subgrade stiffness is within the range of values expected for a subgrade material,
ranging from about 50 to 100 MPa ( 7,250 and 14,500 psi), with a few points in the range of 200
MPa. These results are presented in Table 5.
Table 5. Backcalculated Moduli from Deflections Measured on Top of CTB
Layer Representative Value ( MPa) Typical Range
( MPa)
Cement- treated base ( CTB) 400 200 and 600
Subgrade ( SG) 70 50 to 100
Figure 21 shows the FWD data collection points on each of the ten concrete slabs after
placement. The measurements done at the corners and along the edges of the slab were used to
calculate LTE across the joints ( transverse as well as longitudinally), whereas the center- slab
deflection serves as an indication of the total structural strength of the complete pavement system.
LTE was measured twice, on what would be the approaching and the leaving sides of the joints if the
pavement were open to traffic, so that results from a given “ upper corner” are at the same location
as the “ lower corner” of the subsequent slab, the difference being that the load is on the opposite
side of the joint.
All FWD data recording locations on all 10 slabs are shown in Figure 22. The data showing
the LTE values for the data from both rows A and C can be seen in Figure 23 to Figure 26. Row B
was not done after the placement of the slabs as this row fell exactly on the longitudinal joint of the
slabs ( see Figure 19).
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0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
0 5 10 15 20 25
CTB Modulus ( MPa)
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
0 5 10 15 20 25
Location ( m)
Subgrade Modulus ( MPa)
Row A Row B Row C
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 5 10 15 20 25
Deflection ( mm)
Figure 20. FWD data collected on the CTB layer.
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``
Transverse joint
Edge
Corner upper left Approach slab Corner upper right
Long, Joint left Long, Joint right
Center
Corner lower left Transverse joint Corner lower right
Edge
Leave slab
Direction of data collection
Figure 21. FWD test locations on each Super- Slab ® slab.
4.57m
Row C 3.96m
7.92 m
Row A
22.86m
Figure 22. FWD data collection points on the concrete slabs.
The LTE values are significantly higher after grouting than before. It is obvious that there is
little load transfer prior to the grouting, with LTE values in the range of 5 to 40 percent, and an
average of 16 percent. These values are low, but reveal some LTE through the support layer, as the
dowels are loose and the faces of the joint are not in contact. Trafficking with the HVS on the
ungrouted slabs did not cause a reduction in LTE ( which was not high, as explained). Regardless of
the level of LTE in the ungrouted condition, the grouting caused load transfer to increase to close to
100 percent. This illustrates that most of the LTE in the completed system was transmitted through
the grout and dowels. Table 6 shows the average and the range of the measured LTE. The results
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come from 32 tests with eight transverse joints evaluated in four positions ( eight tests for the “ after
HVS” dataset).
Table 6. Measured Load Transfer Efficiency Before and After
Grouting, Morning and Afternoon
A. M. P. M.
LTE (%) Average Range Average Range
Ungrouted 16 4 to 40 39 8 to 83
UG after HVS 16 6 to 25 67 55 to 79
Grouted 100 92 to 104 98 91 to 102
The effect of temperature on LTE is clearly visible. The average surface temperature
recorded during FWD data collection during the daytime was 41° C ( 106° F) and during the nighttime
it was 21° C ( 70° F). During nighttime, the edges tend to curl upward due to slab contraction and a
negative temperature differential in the concrete ( the surface being colder than the bottom). This
curling effect reduces the load transfer by reducing slab contact with the base at the joints and
corners, which reduces load transfer through the underlying layers. The opposite happens during
daytime when the slabs expand, which causes an increase in load transfer. These temperature
effects were less visible after grouting, which illustrates the effectiveness of the steel dowels and the
grouting in restricting relative vertical movement across the joints even under the influence of
temperature changes.
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Corner Upper Left
0
10
20
30
40
50
60
70
80
90
100
110
120
0 2 4 6 8 10 12 14 16 18 20
Station ( m)
LTE (%)
Row A A. M. Ungrouted Row A P. M. Ungrouted
Row A A. M. Grouted Row A P. M. Grouted
Corner Upper Right
0
10
20
30
40
50
60
70
80
90
100
110
120
0 2 4 6 8 10 12 14 16 18 20
Station ( m)
LTE (%)
Row A A. M. Ungrouted Row A P. M. Ungrouted
Row A A. M. Grouted Row A P. M. Grouted
Corner Lower Left
0
10
20
30
40
50
60
70
80
90
100
110
120
0 2 4 6 8 10 12 14 16 18 20
Station ( m)
LTE (%)
Row A A. M. Ungrouted Row A P. M. Ungrouted
Row A A. M. Grouted Row A P. M. Grouted
Corner Lower Right
0
10
20
30
40
50
60
70
80
90
100
110
120
0 2 4 6 8 10 12 14 16 18 20
Station ( m)
LTE (%)
Row A A. M. Ungrouted Row A P. M. Ungrouted
Row A A. M. Grouted Row A P. M. Grouted
Figure 23. Transverse joint LTE data from the corners of the slabs: Row A.
Stage 5 Distribution
UCPRC- RR- 2006- 10
25
Longitudinal Joint Left Side
0
10
20
30
40
50
60
70
80
90
100
110
120
0 2 4 6 8 10 12 14 16 18 20
Station ( m)
LTE (%)
Row A A. M. Ungrouted Row A P. M. Ungrouted
Row A A. M. Grouted Row A P. M. Grouted
No data : AC shoulder on the right side.
Transverse Joint Approach Edge
0
10
20
30
40
50
60
70
80
90
100
110
120
0 2 4 6 8 10 12 14 16 18 20
Station ( m)
LTE (%)
Row A A. M. Ungrouted Row A P. M. Ungrouted
Row A A. M. Grouted Row A P. M. Grouted
Transverse Joint Leave Edge
0
10
20
30
40
50
60
70
80
90
100
110
120
0 2 4 6 8 10 12 14 16 18 20
Station ( m)
LTE (%)
Row A A. M. Ungrouted Row A P. M. Ungrouted
Row A A. M. Grouted Row A P. M. Grouted
Figure 24. LTE data from mid- slab edge positions: Row A.
Stage 5 Distribution
UCPRC- RR- 2006- 10
26
Corner Upper Left
0
10
20
30
40
50
60
70
80
90
100
110
120
0 2 4 6 8 10 12 14 16 18 20
Station ( m)
LTE (%)
Row C A. M. Ungrouted Row C P. M. Ungrouted
Row C A. M. Ungrouted After HVS Row C P. M. Ungrouted After HVS
Row C A. M. Grouted Row C P. M. Grouted
Corner Upper Right
0
10
20
30
40
50
60
70
80
90
100
110
120
0 2 4 6 8 10 12 14 16 18 20
Station ( m)
LTE (%)
Row C A. M. Ungrouted Row C P. M. Ungrouted
Row C A. M. Ungrouted After HVS Row C P. M. Ungrouted After HVS
Row C A. M. Grouted Row C P. M. Grouted
Corner Lower Left
0
10
20
30
40
50
60
70
80
90
100
110
120
0 2 4 6 8 10 12 14 16 18 20
Station ( m)
LTE (%)
Row C A. M. Ungrouted Row C P. M. Ungrouted
Row C A. M. Ungrouted After HVS Row C P. M. Ungrouted After HVS
Row C A. M. Grouted Row C P. M. Grouted
Corner Lower Right
0
10
20
30
40
50
60
70
80
90
100
110
120
0 2 4 6 8 10 12 14 16 18 20
Station ( m)
LTE (%)
Row C A. M. Ungrouted Row C P. M. Ungrouted
Row C A. M. Ungrouted After HVS Row C P. M. Ungrouted After HVS
Row C A. M. Grouted Row C P. M. Grouted
Figure 25. Transverse joint LTE data from the corners of the slabs: Row C.
Stage 5 Distribution
UCPRC- RR- 2006- 10
27
No data: AC shoulder on left side.
Longitudinal Joint Right Side
0
10
20
30
40
50
60
70
80
90
100
110
120
0 2 4 6 8 10 12 14 16 18 20
Station ( m)
LTE (%)
Row C A. M. Ungrouted Row C P. M. Ungrouted
Row C A. M. Ungrouted After HVS Row C P. M. Ungrouted After HVS
Row C A. M. Grouted Row C P. M. Grouted
Transverse Joint Approach Edge
0
10
20
30
40
50
60
70
80
90
100
110
120
0 2 4 6 8 10 12 14 16 18 20
Station ( m)
LTE (%)
Row C A. M. Ungrouted Row C P. M. Ungrouted
Row C A. M. Ungrouted After HVS Row C P. M. Ungrouted After HVS
Row C A. M. Grouted Row C P. M. Grouted
Transverse Joint Leave Edge
0
10
20
30
40
50
60
70
80
90
100
110
120
0 2 4 6 8 10 12 14 16 18 20
Station ( m)
LTE (%)
Row C A. M. Ungrouted Row C P. M. Ungrouted
Row C A. M. Ungrouted After HVS Row C P. M. Ungrouted After HVS
Row C A. M. Grouted Row C P. M. Grouted
Figure 26. LTE data from the mid- slab edge positions: Row C.
Stage 5 Distribution
UCPRC- RR- 2006- 10
28
Row C: Center Deflections @ 40kN
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 5 10 15 20 25
Station ( m)
Deflection ( mm)
Row C A. M. Ungrouted Row C P. M. Ungrouted
Row C A. M. Ungrouted After HVS Row C P. M. Ungrouted After HVS
Row C A. M. Grouted Row C P. M. Grouted
Row A: Center Deflections @ 40kN
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 5 10 15 20 25
Station ( m)
Deflection ( mm)
Row A A. M. Ungrouted Row A P. M. Ungrouted
Row A A. M. Grouted Row A P. M. Grouted
Surface deflections were recorded with the FWD at the center of each slab as shown in
Figure 21 and Figure 22. These data are shown in Figure 27.
Figure 27. FWD 40kN deflection data.
Stage 5 Distribution
UCPRC- RR- 2006- 10
29
The deflections vary as expected with temperature. The daytime temperature differential
caused the slabs to curl slightly downward which resulted in higher center deflections when
compared to the nighttime measurements. The grouting caused increased load transfer between
slabs which caused the deflections after grouting to be lower than those recorded before
grouting. Statistical summaries of the peak deflections measured at the center of the slabs can
be seen in Table 7 for three testing stages: ( i) ungrouted slab, not yet trafficked, ( ii) ungrouted
slabs after applying 86,500 ESALs with the HVS, and ( iii) after grouting of the joints and slabs.
The average, sample standard deviations, and coefficient of variations for the various cases are
shown in the table. The information presented was compiled from only five slabs per row and due
to the small sample size the derived statistical parameters should be interpreted with caution,
although they are included here to assist in the interpretation of the results.
Table 7. FWD Deflections Measured at Slab Centers on Top of Pre- Cast Slabs
Deflection Ungrouted Ungrouted after
HVS Grouted
Row Parameter A. M. P. M. A. M. P. M. A. M. P. M.
Ave ( mm) 0.199 0.375 n/ a n/ a 0.144 0.321
STD ( mm) 0.025 A 0.072 n/ a n/ a 0.019 0.029
Coef of Var (%) 12.6 19.2 n/ a n/ a 13.5 9.1
Ave ( mm) 0.311 0.375 0.226 0.52 0.119 0.275
C STD ( mm) 0.106 0.072 0.06 0.079 0.012 0.056
Coef of Var (%) 34.1 19.2 26.5 15.2 9.7 20.2
The following observations regarding the peak FWD deflections are made:
• The influence of the day- night temperature variation on the deflection measurements is
significant. Lower center slab deflections were recorded in the early mornings ( slabs
curled upward) in comparison to those recorded in the afternoon ( slabs curled
downward). This is expected because the afternoon curling tends to reduce the contact
stress between the slab and the base caused by gravity and the mass of the slab.
• The maximum center slab deflections were recorded on the ungrouted slabs in the
afternoon where the deflections varied between 0.375 and 0.525 mm ( 14.8 and 21 mils.)
These values are high for newly placed slabs, but are explained by the fact that the slabs
were unconnected ( ungrouted) during time of testing, because of possible voids between
slab and the sand layer, and temperature effects.
• The influence of the grouting is clearly visible where the average deflections showed a
significant drop after the grouting in comparison with before grouting. Deflections varied
between 0.119 and 0.321 mm ( 4.7 and 12.6 mils), which is what is to be expected from
an untrafficked new pavement.
Stage 5 Distribution
UCPRC- RR- 2006- 10
30
• Although limited to a small sample size, the variation in the data is less after grouting
than before. The sections behave more uniformly from a structural standpoint after
grouting than before.
The backcalculated moduli for the concrete, the cemented base, and the subgrade are
presented in Figure 28. The backcalculations were performed using the Elmod © 5 software at
three testing stages: ( i) ungrouted slab, not yet trafficked, ( ii) ungrouted slabs after applying
86,500 ESALs with the HVS, and ( iii) after grouting of the joints and under the slabs. In each
case the deflection data were collected in the early morning at low temperature and also in the
afternoon at a higher temperature. Table 9 shows the average backcalculated moduli for each
row of slabs ( rows A and C), for the various layers, and under the different conditions ( time of
day and testing stage). Results at individual locations are presented in Figure 29 to Figure 31.
The results shown in Figure 28 are the average of all test locations. The morning data is
considered to be provide more reliable results because the testing is at the center of the slab,
which is in contact with the under layers when the temperature differential is negative ( colder on
the surface of the slab).
19,447
2,235
71
4,373
48
19,043
3,531
137
24,331
-
5,000
10,000
15,000
20,000
25,000
30,000
PCC CTB SG
Elastic Modulus ( MPa) .
Morning
12,294
6,540
33
9,265
3,057
28
23,435
112
49
PCC CTB SG
Ungrouted
UG after HVS
Grouted
Afternoon
Figure 28. Backcalculated elastic moduli for the concrete, the cemented base, and the
subgrade, obtained from morning and afternoon deflection data.
Table 8 presents the values considered representative of the materials comprising the
three structural layers of the pavement system.
Stage 5 Distribution
UCPRC- RR- 2006- 10
31
Table 8. Backcalculated Moduli from Deflections Measured on Top of Pre- Cast Slabs
Layer Representative value ( MPa) Typical Range ( MPa)
Portland cement concrete ( PCC)
pre- cast slabs
19,500 5,000 to 30,000
Cement- treated base ( CTB) 2,200 1,000 to 8,000
Subgrade ( SG) 70 20 to 120
The subgrade modulus is consistent with what was obtained from deflection testing
directly on the newly constructed base ( as opposed to these results obtained from deflection
testing on top of the pre- cast panels). The CTB modulus obtained previously, when the material
was up to 14 days old, increased to a more reasonable value, but in the lower range of what
would be expected for a cement- treated base. The testing after grouting took place when the
CTB was approaching 28 days.
Table 9. Detailed results of Backcalculation from Deflections Measured
on Top of Pre— Cast Slabs
Average Moduli
( MPa)
Ungrouted Ungrouted after
HVS
Grouted
Row Layer A. M. P. M. A. M. P. M. A. M. P. M.
PCC 31,000 14,200 n/ a n/ a 16,900 21,700
A CTB 2,983 3,155 n/ a n/ a 3,288 35
SG 75 43 n/ a n/ a 126 50
PCC 12,000 12,125 26,438 8,175 16,750 23,875
C CTB 4,467 10,633 5,775 9,000 4,513 20
SG 74 27 48 28 136 50
The backcalculation results from deflection taken before grouting should be interpreted
with caution. At that stage the slabs were not properly connected and slab rocking could be the
cause of the high degree of variation in the data as seen in the graphs. The data after grouting
are more consistent and in agreement with what are expected values. As seen in the tables and
graphs, there is significant variation within and between the various data sets. As explained
before, the effect of the ungrouted ( not connected) slabs on the variation in surface deflections is
amplified during the backcalculation process. A significant amount of scatter is visible in the
graphs. After grouting the trends are more consistent with a lower degree of variation between
the various slabs.
Stage 5 Distribution
UCPRC- RR- 2006- 10
32
Row A - PCC Modulus
0
5 000
10 000
15 000
20 000
25 000
30 000
35 000
0 5 10 Station ( m) 15 20 25
Modulus ( MPa)
Row A A. M. Ungrouted Row A P. M. Ungrouted
Row A A. M. Grouted Row A P. M. Grouted
Row C - PCC Modulus
0
5 000
10 000
15 000
20 000
25 000
30 000
35 000
0 2 4 6 8 10 12 14 16 18 20
Modulus ( MPa)
Row C A. M. Ungrouted Row C P. M. Ungrouted
Row C A. M. Ungrouted After HVS Row C P. M. Ungrouted After HVS
Row C A. M. Grouted Row C P. M. Grouted
Figure 29. Backcalculated stiffness of concrete layer.
Stage 5 Distribution
UCPRC- RR- 2006- 10
33
Row A - CTB Modulus
0
2 000
4 000
6 000
8 000
10 000
12 000
14 000
0 5 10 Station ( m) 15 20 25
Modulus ( MPa)
Row A A. M. Ungrouted Row A P. M. Ungrouted
Row A A. M. Grouted Row A P. M. Grouted
Row C - CTB Modulus
0
2 000
4 000
6 000
8 000
10 000
12 000
14 000
0 2 4 6 8 10 12 14 16 18 20
Modulus ( MPa)
Row C A. M. Ungrouted Row C P. M. Ungrouted
Row C A. M. Ungrouted After HVS Row C P. M. Ungrouted After HVS
Row C A. M. Grouted Row C P. M. Grouted
Figure 30. Backcalculated stiffness of CTB layer.
Stage 5 Distribution
UCPRC- RR- 2006- 10
34
Row A - Subgrade Modulus
0
20
40
60
80
100
120
140
160
180
0 5 10 Station ( m) 15 20 25
Modulus ( MPa)
Row A A. M. Ungrouted Row A P. M. Ungrouted
Row A A. M. Grouted Row A P. M. Grouted
Row C - Subgrade Modulus
0
20
40
60
80
100
120
140
160
180
0 2 4 6 8 10 12 14 16 18 20
Modulus ( MPa)
Row C A. M. Ungrouted Row C P. M. Ungrouted
Row C A. M. Ungrouted After HVS Row C P. M. Ungrouted After HVS
Row C A. M. Grouted Row C P. M. Grouted
Figure 31. Backcalculated stiffness of subgrade.
2.4 Laboratory Test Results
Beams of 150 by 150 by 450 mm ( 6 by 6 by 18 in.) were cast from the dowel and
bedding grouts at the time of grouting. These beams were tested after one, fourteen, and
twenty- eight days curing to determine the modulus of rupture. Table 10 summarizes the
modulus of rupture results which are plotted in Figure 32 for the dowel grout and in Figure 33 for
Stage 5 Distribution
UCPRC- RR- 2006- 10
35
the bedding grout. It can be seen that the bedding grout is considerably weaker than the dowel
grout, and that the dowel grout has strength similar to that of concrete slabs.
Table 10. Modulus of Rupture ( MPa) Results for the Dowel and Bedding Grout
Dowel Grout Bedding Grout
Curing Age ( days) Curing Age ( days)
1 14 28 1 14 28
3.06 3.89 5.29 1.09 1.21 1.88
3.94 4.52 5.07 1.19 1.21 1.51
5.04 0.87 1.23
3.5* 4.2* 5.1* 1.1* 1.2* 1.7*
* Average modulus of rupture.
Dowel grout
0
1
2
3
4
5
6
0 5 10 15 20 25 30
Curing ( days)
Modulus of Rupture ( MPa)
Figure 32. Dowel grout modulus of rupture plotted against curing time.
Stage 5 Distribution
UCPRC- RR- 2006- 10
36
Bedding grout
0
1
2
3
4
5
6
0 5 10 15 20 25 30
Curing ( days)
Modulus of Rupture ( MPa)
Figure 33. Bedding grout modulus of rupture plotted against curing time.
Stage 5 Distribution
UCPRC- RR- 2006- 10
37
3. TEST SECTIONS NOMENCLATURE AND INSTRUMENTATION
3.1 Test Nomenclature
As mentioned earlier, a test grid consisting of two lanes each with five pre- cast slabs was
constructed for this experiment. Two test sections were established, one on the north side and
one on the south side. These two test sections were designated 597FD and 598FD, according to
the convention for all HVS tests performed by the UCPRC3. Throughout this report these two
test sections are referred to as Test 597FD and Test 598FD. Two specific phases of the
experiment were labeled with two extra letters to indicate “ thermal curling” ( TC), and “ ungrouted”
( UG). This system of nomenclature is consistent with the global HVS database used by the HVS
International Alliance.
Figure 34 shows approximately at scale the length of the HVS with respect to the test
grid. Two joints were studied in each section. The approximate area of the pavement trafficked
with the HVS wheel at each section is also shown.
Figure 34. Schematic of the positioning of the HVS and trafficked areas in tests 597FD and
598FD.
3 The abbreviations FD and RF attached to test section numbers 597 and 598 refer to testing performed under
“ field” conditions and at the Richmond Field Station, respectively.
North HVS Section
Test 597FD
Test 598FD
South HVS Section
Stage 5 Distribution
UCPRC- RR- 2006- 10
38
( a) 597FD test
( b) 598FD test
Figure 35. Photographs of HVS2 during Tests 597FD and 598FD.
3.2 Instrumentation
This section provides an overview of all the instrumentation locations on both lanes of the
test grid of pre- cast slabs. Not all the instruments were used at the same time; the
instrumentation detail of each HVS test is provided in the sections relating to each specific HVS
test. The instrumentation is concentrated mostly on the center column of slabs in the five- by- two
grid. Therefore, standing on the southern longitudinal edge of the slabs looking north and
numbering the slabs from left to right starting at the top, left- hand corner most of the instrument
locations are on slabs 3 and 8 as shown in Figure 36. The symbol “ J” is used to indicate vertical
joint- deflection measurement devices ( JDMD) and the symbol “ H” is used to indicate horizontal
joint- deflection measurement devices. JDMDs are linear displacement measurement devices
that have reference rods anchored away from the slabs, and measure absolute vertical
deformations. Horizontal JDMDs are mounted across joints and measure relative opening and
closing of the joint ( the sensors do not identify the contribution of the individual slabs to the total
deformation).
Stage 5 Distribution
UCPRC- RR- 2006- 10
39
Figure 36. Complete set of thermocouple and JDMD locations.
Thermocouples, indicated by the symbol “ T” in Figure 36, were installed at depths of 10,
60, 110, 160, and 210 mm in the 220- mm thick slabs.
Multi- depth Deflectometers ( MDDs) are vertical displacement measurement devices
installed in the slab. Each module in an MDD is anchored at a different depth in the pavement.
To install a MDD, a 38- mm ( 1.5- in.) hole is first drilled through the pavement. A metal anchor rod
is inserted into the hole and embedded in concrete several meters below the pavement. Gauges
are anchored to the sides of the hole at different depths in the pavement, with the metal rod
passing through them. MDDs were installed close to the location of vertical JDMDs 1, 2, 4, 5, 8,
9, 11, and 12. The MDD modules were installed in the top- cap as close to the surface as
possible, at 230 mm ( 9 in) depth at the top of the CTB, at 380 mm ( 15 in) depth at the bottom of
the CTB, and at 680 mm ( 27 in) depth in the subgrade. All the MDDs and vertical JDMDs were
anchored at a depth of 3 m. Some of the sensor anchors can be seen in Figure 38, where the
wheel trafficked and the diamond ground areas are shown. Figure 38 shows examples of
installed JDMDs and MDDs. Figure 39 illustrates the JDMD instrumentation at the two joints and
at mid- slab for Test 598FD.
Slab 2 Slab 4
Slab 7 Slab 9
J1 J2 J3 J4 J5
J6 J7
J6( a) J7( a)
J8 J9 J10 J11 J12
H13 H14
H17 H18
H15 H16
H15( a) H16( a)
H15( b) H16( b)
T1
T2
T3
T4
T5
T6
T7 T9
T8
N
Stage 5 Distribution
UCPRC- RR- 2006- 10
40
Figure 37. Trafficked test area and some JDMD anchors for Test 597FD.
Figure 38. Examples of JDMDs and MDDs.
Ground area
Trafficked
area
JDMD anchors
JDMD anchor
Vertical JDMDs
Horizontal JDMDs
MDDs
Stage 5 Distribution
UCPRC- RR- 2006- 10
41
Figure 39. Photograph of JDMDs for Test 598FD.
H16( b)
J12 H18
J11 J10
J8, J9,
H15( b)
H17
Stage 5 Distribution
UCPRC- RR- 2006- 10
42
4. TESTS PERFORMED BEFORE GROUTING
4.1 Thermal Curl Test 597FDTC
Before the HVS was placed on the test slabs, the thermal curl of the ungrouted slabs was
tracked over a 24- hour period from 14h00 ( 2 p. m.) on May 27, 2005, to 14h00 on May 28, 2005,
without any loading being applied to the slabs. The instruments monitored on an hourly basis
during this time period are shown in Figure 40.
J2 J3 J4
J6 J7
J9 J10 J11
H15 H16
T1
T2
T3
T4
T5
T6
T7 T9
T8
H13 H14
H17 H18
N
Figure 40. Thermocouples and JDMDs monitored during the thermal curl test on the
ungrouted slabs.
The average slab temperature and temperature gradient were calculated from the
temperature data recorded at five depths for each of the thermocouples shown in Figure 40. The
average slab temperature is shown in Figure 41 and the temperature gradient in Figure 42. The
JDMDs can only measure the relative movement of the slab since the start of the test with no
indication of the neutral position of the slab. An assumption therefore had to be made that the
slabs were in a neutral position at the time the temperature gradient was zero. This occurred on
two occasions, between 18h00 and 19h00 on May 27, 2005, and between 09h00 and 10h00 on
May 28, 2005. The JDMD readings at 10h00 on May 28, 2005, were therefore assumed to
represent the neutral position of the slab and all other measurements were adjusted relative to
the measurement taken at this time.
Stage 5 Distribution
UCPRC- RR- 2006- 10
43
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
27/ 05: 12: 00
27/ 05: 13: 00
27/ 05: 14: 00
27/ 05: 15: 00
27/ 05: 16: 00
27/ 05: 17: 00
27/ 05: 18: 00
27/ 05: 19: 00
27/ 05: 20: 00
27/ 05: 21: 00
27/ 05: 22: 00
27/ 05: 23: 00
28/ 05: 00: 00
28/ 05: 01: 00
28/ 05: 02: 00
28/ 05: 03: 00
28/ 05: 04: 00
28/ 05: 05: 00
28/ 05: 06: 00
28/ 05: 07: 00
28/ 05: 08: 00
28/ 05: 09: 00
28/ 05: 10: 00
28/ 05: 11: 00
28/ 05: 12: 00
28/ 05: 13: 00
28/ 05: 14: 00
28/ 05: 15: 00
28/ 05: 16: 00
Date & Time
Ave slab temperature ( oC)
TC 1
TC 2
TC 4
TC 3
TC 6
TC 7
TC 8
TC 9
Figure 41. Average slab temperature during the ungrouted thermal curl test.
- 0.60
- 0.40
- 0.20
0.00
0.20
0.40
0.60
0.80
1.00
27/ 05: 12: 00
27/ 05: 13: 00
27/ 05: 14: 00
27/ 05: 15: 00
27/ 05: 16: 00
27/ 05: 17: 00
27/ 05: 18: 00
27/ 05: 19: 00
27/ 05: 20: 00
27/ 05: 21: 00
27/ 05: 22: 00
27/ 05: 23: 00
28/ 05: 00: 00
28/ 05: 01: 00
28/ 05: 02: 00
28/ 05: 03: 00
28/ 05: 04: 00
28/ 05: 05: 00
28/ 05: 06: 00
28/ 05: 07: 00
28/ 05: 08: 00
28/ 05: 09: 00
28/ 05: 10: 00
28/ 05: 11: 00
28/ 05: 12: 00
28/ 05: 13: 00
28/ 05: 14: 00
28/ 05: 15: 00
28/ 05: 16: 00
Date & Time
Temperature gradient ( oC/ cm)
TC 1
TC 2
TC 4
TC 3
TC 6
TC 7
TC 8
TC 9
Figure 42. Temperature gradient during the ungrouted thermal curl test.
Figure 43 shows the relative movement ( in terms of the previously determined neutral
position) of the all the vertical JDMDs shown in Figure 40 at the corners of the slabs. As
expected, the corners of the slabs curled upward during nighttime when the slabs had a negative
Stage 5 Distribution
UCPRC- RR- 2006- 10
44
temperature gradient ( warmer at the bottom than at the top of the slab). Figure 44 shows the
adjusted joint activity recorded by the horizontal JDMDs. Again, as expected the joints closed up
at the higher temperatures during daytime. The highest vertical movement occurred at JDMD 6
with a range from 1.5 mm downward to 1.5 mm upward ( 3 mm total) and the smallest movement
occurred at JDMD 4 with a range from 0.5 mm downward to 0.5 mm upward ( 1 mm total). The
range of joint opening and closing was from 0.2 mm to - 0.8 mm giving a total joint activity of
1 mm.
In an effort to determine the relationship between temperature gradient and vertical curl,
the adjusted JDMD readings were plotted with the temperature gradient data. Figure 45 shows a
typical example of the adjusted vertical movement at JDMD 9 plotted with the temperature
gradient calculated from the temperature data for the closest thermocouple, TC7. It is apparent
that the vertical curl is correlated to the temperature gradient.
- 2
- 1.5
- 1
- 0.5
0
0.5
1
1.5
2
27/ 05: 12: 00
27/ 05: 13: 00
27/ 05: 14: 00
27/ 05: 15: 00
27/ 05: 16: 00
27/ 05: 17: 00
27/ 05: 18: 00
27/ 05: 19: 00
27/ 05: 20: 00
27/ 05: 21: 00
27/ 05: 22: 00
27/ 05: 23: 00
28/ 05: 00: 00
28/ 05: 01: 00
28/ 05: 02: 00
28/ 05: 03: 00
28/ 05: 04: 00
28/ 05: 05: 00
28/ 05: 06: 00
28/ 05: 07: 00
28/ 05: 08: 00
28/ 05: 09: 00
28/ 05: 10: 00
28/ 05: 11: 00
28/ 05: 12: 00
28/ 05: 13: 00
28/ 05: 14: 00
Date & Time
Relative position ( mm)
Negative is upwards
JDMD2
JDMD4
JDMD6
JDMD7
JDMD9
JDMD11
Figure 43. Adjusted vertical movement of the slab corners during the ungrouted thermal
curl test.
Stage 5 Distribution
UCPRC- RR- 2006- 10
45
- 1
- 0.8
- 0.6
- 0.4
- 0.2
0
0.2
0.4
0.6
0.8
1
27/ 05: 12: 00
27/ 05: 13: 00
27/ 05: 14: 00
27/ 05: 15: 00
27/ 05: 16: 00
27/ 05: 17: 00
27/ 05: 18: 00
27/ 05: 19: 00
27/ 05: 20: 00
27/ 05: 21: 00
27/ 05: 22: 00
27/ 05: 23: 00
28/ 05: 00: 00
28/ 05: 01: 00
28/ 05: 02: 00
28/ 05: 03: 00
28/ 05: 04: 00
28/ 05: 05: 00
28/ 05: 06: 00
28/ 05: 07: 00
28/ 05: 08: 00
28/ 05: 09: 00
28/ 05: 10: 00
28/ 05: 11: 00
28/ 05: 12: 00
28/ 05: 13: 00
28/ 05: 14: 00
Date & Time
Relative position ( mm)
Negative is closing
H13
H14
H15
H16
H17
H18
Figure 44. Adjusted horizontal joint activity during the ungrouted thermal curl test.
- 1.5
- 1.25
- 1
- 0.75
- 0.5
- 0.25
0
0.25
0.5
0.75
1
1.25
1.5 27/ 05: 12: 00
27/ 05: 13: 00
27/ 05: 14: 00
27/ 05: 15: 00
27/ 05: 16: 00
27/ 05: 17: 00
27/ 05: 18: 00
27/ 05: 19: 00
27/ 05: 20: 00
27/ 05: 21: 00
27/ 05: 22: 00
27/ 05: 23: 00
28/ 05: 00: 00
28/ 05: 01: 00
28/ 05: 02: 00
28/ 05: 03: 00
28/ 05: 04: 00
28/ 05: 05: 00
28/ 05: 06: 00
28/ 05: 07: 00
28/ 05: 08: 00
28/ 05: 09: 00
28/ 05: 10: 00
28/ 05: 11: 00
28/ 05: 12: 00
28/ 05: 13: 00
28/ 05: 14: 00
Date & Time
Relative position ( mm)
Negative is upwards
- 0.75
- 0.5
- 0.25
0
0.25
0.5
0.75
Temperature gradient ( oC/ cm)
JDMD 9
TC 7
Figure 45. Example of the relationship between the temperature gradient and vertical
movement of the slab corners.
Stage 5 Distribution
UCPRC- RR- 2006- 10
46
This correlation was explored further by plotting the adjusted vertical corner movement
against the temperature gradient for the JDMDs with thermocouples in close proximity. The
results from this process are shown in Figure 46.
- 1.5
- 1
- 0.5
0
0.5
1
1.5
- 0.8 - 0.6 - 0.4 - 0.2 0 0.2 0.4 0.6 0.8
Temperature gradient ( oC/ cm)
Relative position ( mm)
Negative is upwards
JDMD2
JDMD4
JDMD9
JDMD11
Figure 46. The correlation between the temperature gradient and vertical movement of the
slab corners.
The response at JDMD 4 seems to be more constrained than at the other JDMDs with
1 mm less total movement at JDMD 4 over the same range of temperature gradient experienced
by the other slab corners, and it is simply an indication of small asymmetric deformations that
could be caused by a difference in support conditions, small geometric differences in the slab, or
non- uniform joint width. JDMD 4 and 11 were located on the doweled side of their respective
slabs, while JDMD 2 and 9 were on the slotted side of the slabs. This could have resulted in a
reduced range of vertical movement at JDMD 4 and 11 compared to JDMD 2 and 9. However,
only JDMD 4 experienced less movement.
A similar analysis was done for the horizontal joint activity by plotting the horizontal
deformation ( opening and closing of the joint) against temperature gradient as shown in Figure
47. Temperature gradient is primarily responsible for rotation of the joint faces, although it is also
an indirect measure of average temperature in the slab. This is the likely reason for the apparent
nonlinearity of the relation between deformation and temperature gradient. Horizontal joint
activity was also plotted against the temperature recorded by the surface thermocouple sensors.
Stage 5 Distribution
UCPRC- RR- 2006- 10
47
The result from this process is shown in Figure 48 and yields a much more linear correlation
between the two parameters.
- 0.8
- 0.6
- 0.4
- 0.2
0
0.2
0.4
0.6
0.8
- 0.8 - 0.6 - 0.4 - 0.2 0 0.2 0.4 0.6 0.8
Temperature gradient ( oC/ cm)
Joint activity ( mm)
Positive is opening
H 13
H 14
H 17
H 18
Figure 47. The correlation between temperature gradient and horizontal joint activity
- 0.8
- 0.6
- 0.4
- 0.2
0
0.2
0.4
0.6
0.8
0 5 10 15 20 25 30 35 40 45
Surface temperature ( oC)
Joint activity ( mm)
Positive is opening
H 13
H 14
H 17
H 18
Figure 48. The correlation between the surface temperature and horizontal joint activity.
In summary the following observations are made regarding the ungrouted thermal curl
test:
Stage 5 Distribution
UCPRC- RR- 2006- 10
48
• The vertical curl at the corners of the unrestrained slabs varied over a range from 1 mm
at JDMD 4 to 3 mm at JDMD 6 for a temperature gradient ranging from - 0.4° C/ cm to
+ 0.8° C/ cm ( temperature differential top to bottom of - 9° C to + 17° C);
• The horizontal joint activity had a total movement of 1 mm for a surface temperature
range from approximately 20° C to 40° C;
• There is a strong linear correlation between the temperature gradient and the vertical
movement at the slab corners caused by thermal curl; and
• There is a strong linear correlation between the surface temperature and horizontal joint
activity.
4.2 Ungrouted Load Tests Background
Two HVS tests were performed on the ungrouted slabs to simulate the exposure of the
ungrouted Super- Slab ® System to traffic from the time of placement to the time of grouting which
normally occurs during the next nighttime closure. These tests were performed on the central
three slabs of each row of the five- by- two grid to ensure that both lanes were exposed to the
same loading conditions in the ungrouted state. In addition to the thermal movement, the
resilient deflection of the ungrouted slabs was also recorded in sets of three load cycles taken at
hourly intervals during these tests.
The traffic loading for the ungrouted tests was determined from an Average Daily Truck
Traffic ( ADTT) count of 6,767 for the southbound direction of I- 15 in 2000 as provided by
Caltrans District 8 and the assumption that the contractor would be able to get back to the site to
grout it the next night after placement of the slabs. The ADTT of 6,767 was compounded to the
year 2005 with a 3 percent growth rate per annum giving an ADTT of 7,853 for 2005. Eighty
percent of the truck traffic was assumed to run on the slow lane giving 6,282 trucks per day on
the outer truck lane. Given a period of 16 out of 24 hours that the ungrouted pavement will be
open to traffic, a further 33 percent reduction was applied to this number resulting in 4,146 trucks
in the outer truck lane from one nighttime closure to the next. Assuming 3.8 ESALs per truck, a
total of 15,756 ESALs had to be applied. The unidirectional production rate of the HVS is 500
repetitions per hour, therefore requiring 31.5 hours of testing. The duration of the ungrouted
tests was therefore set at a minimum of 32 hours to achieve the required traffic loading. The
traffic load for the ungrouted tests was planned to be a 40 kN half- axle load, the equivalent of an
ESAL, but because of a systematic error in the calibration of the HVS wheel load, the actual
wheel load was 60 kN, resulting in the equivalent of approximately 86,500 ESALs being applied
to each section during the ungrouted tests.
Stage 5 Distribution
UCPRC- RR- 2006- 10
49
4.3 Load Test 597FDUG
Figure 49 shows the instrumentation layout for the first ungrouted test, 597FDUG which
started at 06h06 on May29, 2005, and ended at 17h27 on May 30, 2005, at 16,002 repetitions of
a 60- kN load applied in unidirectional mode from the cabin to the tow- end of the HVS ( from west
to east or from left to right in terms of the layout shown in Figure 49).
J1 J2 J3 J4 J5
J6 J7
J10
H13 H14
H15 H16
H15( a) H16( a)
T1
T2
T3
T4
T5
T6
T7 T9
T8
N
Approximate area shaded by the HVS
Traffic side
Caravan side
Cabin- end
Tow- end
Figure 49. Thermocouples and JDMDs monitored during the first ungrouted test,
597FDUG.
The average slab temperature and temperature gradient were calculated from the
temperature data recorded at the five depths for each of the thermocouples shown in Figure 49.
The average slab temperature is shown in Figure 50 and the temperature gradient in Figure 51.
The temperature moved in a narrow band between 20 and 25° C ( 67 and 75° F) for most of the
test and only exceeded 25° C from 11h00 on May 30, 2005, at a few of the thermocouple
locations. The shading effect of the shadow of the HVS on the test section is apparent from the
temperature data, with thermocouples 1 to 4 having a lower temperature and temperature
gradient after 11h00 on May 30, 2005, than the exposed thermocouples ( TCs 5 to 9). The time
of zero temperature gradient is also different for the shielded and exposed thermocouples. The
exposed thermocouples reached a zero temperature gradient at 11h00 on May 29, 2005, and the
shielded thermocouples only reached a zero temperature gradient at 12h00 on May 30, 2005.
Stage 5 Distribution
UCPRC- RR- 2006- 10
50
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
29/ 05: 06: 00
29/ 05: 07: 00
29/ 05: 08: 00
29/ 05: 09: 00
29/ 05: 10: 00
29/ 05: 11: 00
29/ 05: 12: 00
29/ 05: 13: 00
29/ 05: 14: 00
29/ 05: 15: 00
29/ 05: 16: 00
29/ 05: 17: 00
29/ 05: 18: 00
29/ 05: 19: 00
29/ 05: 20: 00
29/ 05: 21: 00
29/ 05: 22: 00
29/ 05: 23: 00
30/ 05: 00: 00
30/ 05: 01: 00
30/ 05: 02: 00
30/ 05: 03: 00
30/ 05: 04: 00
30/ 05: 05: 00
30/ 05: 06: 00
30/ 05: 07: 00
30/ 05: 08: 00
30/ 05: 09: 00
30/ 05: 10: 00
30/ 05: 11: 00
30/ 05: 12: 00
30/ 05: 13: 00
30/ 05: 14: 00
30/ 05: 15: 00
30/ 05: 16: 00
Date & Time
Average slab temperature ( oC)
TC 1
TC 2
TC 3
TC 4
TC 5
TC 6
TC 7
TC 8
TC 9
Figure 50. Average slab temperature during the ungrouted test, 597FDUG.
- 1.00
- 0.80
- 0.60
- 0.40
- 0.20
0.00
0.20
0.40
0.60
0.80
1.00
29/ 05 06: 00
29/ 05 07: 00
29/ 05 08: 00
29/ 05 09: 00
29/ 05 10: 00
29/ 05 11: 00
29/ 05 12: 00
29/ 05 13: 00
29/ 05 14: 00
29/ 05 15: 00
29/ 05 16: 00
29/ 05 17: 00
29/ 05 18: 00
29/ 05 19: 00
29/ 05 20: 00
29/ 05 21: 00
29/ 05 22: 00
29/ 05 23: 00
30/ 05 00: 00
30/ 05 01: 00
30/ 05 02: 00
30/ 05 03: 00
30/ 05 04: 00
30/ 05 05: 00
30/ 05 06: 00
30/ 05 07: 00
30/ 05 08: 00
30/ 05 09: 00
30/ 05 10: 00
30/ 05 11: 00
30/ 05 12: 00
30/ 05 13: 00
30/ 05 14: 00
30/ 05 15: 00
30/ 05 16: 00
Date & Time
Temperature gradient ( oC/ cm)
TC 1
TC 2
TC 3
TC 4
TC 5
TC 6
TC 7
TC 8
TC 9
Figure 51. Temperature gradient during the ungrouted test, 597FDUG.
The JDMD readings at 11h00 on May 29, 2005, were therefore assumed to represent the
neutral position for the vertical JDMDs 1 to 5 and horizontal JDMDs 13, 14, 15( a), and 16( a)
( sensor location shown in Figure 49). The JDMD readings at 12h00 on May 30, 2005, were
Stage 5 Distribution
UCPRC- RR- 2006- 10
51
assumed to represent the neutral position for the vertical JDMDs 6, 7, and 10, and horizontal
JDMDs 15 and 16.
Two types of displacement measurements were taken with the JDMDs: the transient
thermal curl of the slabs and the resilient load related deflection. The transient thermal curl of the
slabs represents the unloaded condition of the slabs and slowly changes with time as the
temperature conditions change while the resilient deflection rapidly increases and rebounds as
the wheel passes over a specific point on the pavement.
4.3.1 Thermal Curl Response
Figure 52 and Figure 53 show the transient thermal curl behavior of the slabs during the
ungrouted load test 597FDUG in terms of the vertical corner positions and joint activity. Figure
54 and Figure 55 show the difference in the temperature gradient and thermal curl of a slab
corner shielded by the HVS compared to an exposed corner. Regardless of these differences,
the thermal curl of the shielded and exposed slab corners are determined by the temperature
gradient as illustrated by Figure 56 for the shielded corners and Figure 57 for the exposed
corners. The relationship between transverse and longitudinal joint thermal curl activity and
surface temperature is shown in Figure 58 for the transverse joints and Figure 59 for the
longitudinal joints.
- 1.5
- 1
- 0.5
0
0.5
1
1.5
29/ 05: 06: 00
29/ 05: 07: 00
29/ 05: 08: 00
29/ 05: 09: 00
29/ 05: 10: 00
29/ 05: 11: 00
29/ 05: 12: 00
29/ 05: 13: 00
29/ 05: 14: 00
29/ 05: 15: 00
29/ 05: 16: 00
29/ 05: 17: 00
29/ 05: 18: 00
29/ 05: 19: 00
29/ 05: 20: 00
29/ 05: 21: 00
29/ 05: 22: 00
29/ 05: 23: 00
30/ 05: 00: 00
30/ 05: 01: 00
30/ 05: 02: 00
30/ 05: 03: 00
30/ 05: 04: 00
30/ 05: 05: 00
30/ 05: 06: 00
30/ 05: 07: 00
30/ 05: 08: 00
30/ 05: 09: 00
30/ 05: 10: 00
30/ 05: 11: 00
30/ 05: 12: 00
30/ 05: 13: 00
30/ 05: 14: 00
30/ 05: 15: 00
30/ 05: 16: 00
Date & Time
Relative position ( mm)
Negative is upwards
JDMD 1
JDMD 2
JDMD 4
JDMD 5
JDMD 6
JDMD 7
Figure 52. Adjusted thermal curl vertical position of the slab corners during the ungrouted
load test, 597FDUG.
Stage 5 Distribution
UCPRC- RR- 2006- 10
52
- 1.5
- 1
- 0.5
0
0.5
1
1.5
29/ 05: 06: 00
29/ 05: 07: 00
29/ 05: 08: 00
29/ 05: 09: 00
29/ 05: 10: 00
29/ 05: 11: 00
29/ 05: 12: 00
29/ 05: 13: 00
29/ 05: 14: 00
29/ 05: 15: 00
29/ 05: 16: 00
29/ 05: 17: 00
29/ 05: 18: 00
29/ 05: 19: 00
29/ 05: 20: 00
29/ 05: 21: 00
29/ 05: 22: 00
29/ 05: 23: 00
30/ 05: 00: 00
30/ 05: 01: 00
30/ 05: 02: 00
30/ 05: 03: 00
30/ 05: 04: 00
30/ 05: 05: 00
30/ 05: 06: 00
30/ 05: 07: 00
30/ 05: 08: 00
30/ 05: 09: 00
30/ 05: 10: 00
30/ 05: 11: 00
30/ 05: 12: 00
30/ 05: 13: 00
30/ 05: 14: 00
30/ 05: 15: 00
30/ 05: 16: 00
Date & Time
Relative position ( mm)
Negative is closing
H 13
H 14
H 15
H 15a
H 16
H 16a
Figure 53. Adjusted thermal curl horizontal joint activity during the ungrouted load test,
597FDUG.
- 1.5
- 1
- 0.5
0
0.5
1
1.5
29/ 05: 06: 00
29/ 05: 07: 00
29/ 05: 08: 00
29/ 05: 09: 00
29/ 05: 10: 00
29/ 05: 11: 00
29/ 05: 12: 00
29/ 05: 13: 00
29/ 05: 14: 00
29/ 05: 15: 00
29/ 05: 16: 00
29/ 05: 17: 00
29/ 05: 18: 00
29/ 05: 19: 00
29/ 05: 20: 00
29/ 05: 21: 00
29/ 05: 22: 00
29/ 05: 23: 00
30/ 05: 00: 00
30/ 05: 01: 00
30/ 05: 02: 00
30/ 05: 03: 00
30/ 05: 04: 00
30/ 05: 05: 00
30/ 05: 06: 00
30/ 05: 07: 00
30/ 05: 08: 00
30/ 05: 09: 00
30/ 05: 10: 00
30/ 05: 11: 00
30/ 05: 12: 00
30/ 05: 13: 00
30/ 05: 14: 00
30/ 05: 15: 00
30/ 05: 16: 00
Date & Time
Relative position ( mm)
Negative is upwards
- 1
- 0.75
- 0.5
- 0.25
0
0.25
0.5
0.75
1
Temperature gradient ( oC/ cm)
JDMD 5
TC 3
Figure 54. Adjusted thermal curl vertical position and temperature gradient for a shielded
slab corner during the ungrouted load test, 597FDUG.
Stage 5 Distribution
UCPRC- RR- 2006- 10
53
- 1.5
- 1
- 0.5
0
0.5
1
1.5
29/ 05: 06: 00
29/ 05: 07: 00
29/ 05: 08: 00
29/ 05: 09: 00
29/ 05: 10: 00
29/ 05: 11: 00
29/ 05: 12: 00
29/ 05: 13: 00
29/ 05: 14: 00
29/ 05: 15: 00
29/ 05: 16: 00
29/ 05: 17: 00
29/ 05: 18: 00
29/ 05: 19: 00
29/ 05: 20: 00
29/ 05: 21: 00
29/ 05: 22: 00
29/ 05: 23: 00
30/ 05: 00: 00
30/ 05: 01: 00
30/ 05: 02: 00
30/ 05: 03: 00
30/ 05: 04: 00
30/ 05: 05: 00
30/ 05: 06: 00
30/ 05: 07: 00
30/ 05: 08: 00
30/ 05: 09: 00
30/ 05: 10: 00
30/ 05: 11: 00
30/ 05: 12: 00
30/ 05: 13: 00
30/ 05: 14: 00
30/ 05: 15: 00
30/ 05: 16: 00
Date & Time
Relative position ( mm)
Negative is upwards
- 1
- 0.75
- 0.5
- 0.25
0
0.25
0.5
0.75
1
Temperature gradient ( oC/ cm) JDMD 7
TC 9
Figure 55. Adjusted thermal curl vertical position and temperature gradient for an exposed
slab corner during the ungrouted load test, 597FDUG.
- 1.5
- 1
- 0.5
0
0.5
1
1.5
- 0.8 - 0.6 - 0.4 - 0.2 0 0.2 0.4 0.6 0.8
Temperature gradient ( oC/ cm)
Relative position ( mm)
Negative is upwards
JDMD 1
JDMD 2
JDMD 4
JDMD 5
Figure 56. Relationship between thermal curl and temperature gradient for the shielded
slab corners during the ungrouted load test, 597FDUG.
Stage 5 Distribution
UCPRC- RR- 2006- 10
54
- 1.5
- 1
- 0.5
0
0.5
1
1.5
- 0.8 - 0.6 - 0.4 - 0.2 0 0.2 0.4 0.6 0.8
Temperature gradient ( oC/ cm)
Relative position ( mm)
Negative is upwards
JDMD 6
JDMD 7
Figure 57. Relationship between thermal curl and temperature gradient for the exposed
slab corners during the ungrouted load test, 597FDUG.
- 1.5
- 1
- 0.5
0
0.5
1
1.5
15 20 25 30 35 40 45
Surface temperature ( oC)
Joint activity ( mm)
Positive is opening
H 13
H 14
Figure 58. Relationship between transverse joint horizontal deformation caused by
thermal curl activity and surface temperature during the ungrouted load test, 597FDUG.
Stage 5 Distribution
UCPRC- RR- 2006- 10
55
- 1.5
- 1
- 0.5
0
0.5
1
1.5
15 20 25 30 35 40 45
Surface temperature ( oC)
Joint activity ( mm)
Positive is opening
H 15
H 15a
H 16
H 16a
Figure 59. Relationship between longitudinal joint horizontal deformation caused by
thermal curl activity and surface temperature during the ungrouted load test, 597FDUG.
4.3.2 Resilient Deflection Response
Figure 60 and Figure 61 show the vertical deflection influence lines for the first and
second joints, respectively, on Test 597FDUG at the end of the HVS test. The response at the
first joint is symmetrical with an equal amount of resilient vertical deflection of almost 1 mm at the
two corners on either side of the joint. There is very little load transfer at the joint with the
deflection recorded by JDMD 1 immediately rebounding to zero as the wheel leaves the
approach slab. The influence line for JDMD 2 shows that the slab rocked around its transverse
axis and the corner at JDMD 2 lifted by about 0.1 mm when the wheel was at the far end of the
slab. The response was similar at the second joint where JDMDs 4 and 5 were installed.
However, the corner where JDMD 4 was installed is either better supported or the slab is stiffer
there than at the other corners as its deflection was significantly lower.
Stage 5 Distribution
UCPRC- RR- 2006- 10
56
- 0.400
- 0.200
0.000
0.200
0.400
0.600
0.800
1.000
0 1 2 3 4 5 6 7 8
Distance ( m)
Deflection ( mm)
JDMD 1
JDMD 2
Cycles: 32001, 32003,
32005
Figure 60. Resilient vertical corner deflection influence lines for the first joint on the
ungrouted load test, 597FDUG.
- 0.400
- 0.200
0.000
0.200
0.400
0.600
0.800
1.000
0 1 2 3 4 5 6 7 8
Distance ( m)
Deflection ( mm)
JDMD 4
JDMD 5
Cycles: 32001, 32003,
32005
Figure 61. Resilient vertical corner deflection influence lines for the second joint on the
ungrouted load test, 597FDUG.
Stage 5 Distribution
UCPRC- RR- 2006- 10
57
The vertical deflection influence lines from JDMDs 6 and 7 installed at the untrafficked
corners of the test slab also showed that the slab rocked around its transverse axis, with the
response at JDMD 6 being synchronized with the response of JDMD 2 and JDMD 7 with JDMD 4
as is shown in Figure 62. The vertical mid- slab deflection influence lines plotted in Figure 63
show that even the mid- slab position on the trafficked slab ( JDMD 3) lifted slightly when the
wheel load was at either edge of the slab. There was, however, no load transfer to the far side of
the untrafficked slab ( JDMD 10).
- 0.400
- 0.200
0.000
0.200
0.400
0.600
0.800
1.000
0 1 2 3 4 5 6 7 8
Distance ( m)
Deflection ( mm)
JDMD 6
JDMD 7
Cycles: 32001, 32003,
32005
Figure 62. Resilient vertical corner deflection influence lines for the untrafficked side on
the ungrouted load test, 597FDUG.
Stage 5 Distribution
UCPRC- RR- 2006- 10
58
- 0.400
- 0.200
0.000
0.200
0.400
0.600
0.800
1.000
0 1 2 3 4 5 6 7 8
Distance ( m)
Deflection ( mm)
JDMD 3
JDMD 10
Cycles: 32001, 32003,
32005
Figure 63. Resilient vertical mid- slab deflection influence lines for the ungrouted load test,
597FDUG.
- 0.400
- 0.200
0.000
0.200
0.400
0.600
0.800
1.000
0 1 2 3 4 5 6 7 8
Distance ( m)
Resilient joint activity ( mm)
( Negative is closing)
H 15a
H 16a
Cycles: 32001, 32003,
32005
Figure 64. Resilient shoulder joint activity influence lines for the ungrouted load test,
597FDUG.
Stage 5 Distribution
UCPRC- RR- 2006- 10
59
The resilient activity was minimal at the shoulder joint ( Figure 64) and longitudinal joint
( Figure 65).
- 0.400
- 0.200
0.000
0.200
0.400
0.600
0.800
1.000
0 1 2 3 4 5 6 7 8
Distance ( m)
Resilient joint activity ( mm)
( Negative is closing)
H 15
H 16
Cycles: 32001,
32003, 32005
Figure 65. Resilient longitudinal joint activity influence lines for the ungrouted load test,
597FDUG.
Figure 66 shows the resilient transverse joint activity calculated from the horizontal
JDMDs H13 and H14. Due to downward rotation of the slab edge under the load, the upper
portion ( sensors were located at the surface) of the transverse joints closed when the wheel was
in the vicinity of the joint and opened when the wheel was on the far end of the slab.
Stage 5 Distribution
UCPRC- RR- 2006- 10
60
- 0.400
- 0.200
0.000
0.200
0.400
0.600
0.800
1.000
0 1 2 3 4 5 6 7 8
Distance ( m)
Resilient joint activity ( mm)
( Negative is closing)
H 13
H 14
Cycles: 32001, 32003,
32005
Figure 66. Resilient transverse joint activity horizontal deformation influence lines for the
ungrouted load test, 597FDUG.
The resilient vertical corner deflections, of which examples are shown in Figure 60 and
Figure 61, were used to calculate the load transfer efficiency at the ungrouted joints. The
formulation of the Load Transfer Efficiency ( LTE) is shown in Figure 67. This formulation is
based on the assumption that the amount of deflection transferred from the approach slab to the
leave slab when the approach slab is loaded, is proportional to the load transferred from the
approach slab to the leave slab. This is the same definition used for FWD tests. An alternative
definition has also been used on other HVS tests that correspond to Westergaard’s definition of
load transfer efficiency ( 6, 7).
Stage 5 Distribution
UCPRC- RR- 2006- 10
61
- 0.200
Distance ( m)
Deflection ( mm)
JDMD 1
JDMD 2
Load
δa
δb
Load Transfer Efficiency ( LTE)= δb/ δa
δa = Peak deflection on approach slab
δb = Simultaneous deflection on leave slab
0.000
0.200
0.400
0.600
0.800
1.000
0 1 2 3 4 5 6 7 8
Figure 67. Formulation of the Load Transfer Efficiency.
Figure 68 shows the peak approach slab and simultaneous leave slab deflection at the
two trafficked joints of the ungrouted test, 597FDUG. The resilient vertical deflection at JDMD 4
was consistently low throughout the duration of the test. Figure 69 shows the LTE for the
duration of the ungrouted test, 597FDUG ( approximately 16,000 wheel- load repetitions over a
32- hr period) 4. In general the LTE was below 20 percent for the duration of the test and only
exceeded this level when the deflection at JDMD 4 was approached by the deflection at JDMD 5,
not because of load transfer but because of the very low deflection recorded at JDMD 4.
4 Plots in Figure 68 to Figure 71 show 32,000 load repetitions in the horizontal axis, but since unidirectional traffic
was used, the actual number of load passes is 16,000.
Stage 5 Distribution
UCPRC- RR- 2006- 10
62
- 0.200
0.000
0.200
0.400
0.600
0.800
1.000
1.200
1.400
1.600
1.800
0 5000 10000 15000 20000 25000 30000 35000
Repetitions
Deflection ( mm)
δa
δb
( a) Ungrouted joint at JDMDs 1 and 2
- 0.200
0.000
0.200
0.400
0.600
0.800
1.000
1.200
1.400
1.600
1.800
0 5000 10000 15000 20000 25000 30000 35000
Repetitions
Deflection ( mm)
δa
δb
( b) Ungrouted joint at JDMDs 4 and 5
Figure 68. Peak approach slab and simultaneous leave slab deflection for the ungrouted
Stage 5 Distribution
UCPRC- RR- 2006- 10
63
load test, 597FDUG.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 5000 10000 15000 20000 25000 30000 35000
Repetitions
Load Transfer Efficiency (%)
JDMDs 1 & 2
JDMDs 4 & 5
Figure 69. Load Transfer Efficiency for the ungrouted test, 597FDUG.
The resilient transverse joint horizontal deformation activity is shown in Figure 70 for the
two trafficked transverse joints on the ungrouted test, 597FDUG. In general the total resilient
joint activity was between 0.3 and 0.4 mm at H13 and between 0.2 and 0.3 mm at H14.
Figure 71 shows the mid- slab deflection for the duration of the ungrouted test, 597FDUG.
Substantial lifting of about 0.1 mm occurred at the mid- slab position for the duration of the test
while the downward deflection under the load was about 0.15 mm, resulting in a total mid- slab
resilient movement of about 0.25 mm for the duration of the test.
Stage 5 Distribution
UCPRC- RR- 2006- 10
64
- 0.400
- 0.300
- 0.200
- 0.100
0.000
0.100
0.200
0.300
0.400
0.500
0 5000 10000 15000 20000 25000 30000 35000
Repetitions
Joint activity ( mm)
( Negative is closing)
Close
Open
Change
( a) Ungrouted joint at horizontal JDMD H13
- 0.300
- 0.200
- 0.100
0.000
0.100
0.200
0.300
0.400
0 5000 10000 15000 20000 25000 30000 35000
Repetitions Joint activity ( mm)
( Negative is closing)
Close
Open
Change
( b) Ungrouted joint at horizontal JDMD H14
Stage 5 Distribution
UCPRC- RR- 2006- 10
65
Figure 70. Transverse joint activity for the ungrouted load test, 597FDUG.
- 0.200
- 0.150
- 0.100
- 0.050
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0 5000 10000 15000 20000 25000 30000 35000
Repetitions
Mid- slab deflection ( mm)
( Negative is upwards)
Up
Down
Change
Figure 71. Mid- slab deflection for the ungrouted test, 597FDUG.
The peak resilient deflections plotted in Figure 68, Figure 70, and Figure 71 presented
daily variations. The effects of the temperature and sunlight exposure conditions ( shade
projected on the pavement by the HVS versus exposed pavement) on the resilient deflections
was therefore investigated. Figure 72 shows the resilient vertical deflection of the shaded
corners plotted against the temperature gradient of the slab. The slab corner at JDMD 4 clearly
had the lowest deflection but there is a correlation between the resilient vertical deflection and
the temperature gradient of the slab for the other slab corners. Figure 73 shows the resilient
vertical deflection of the exposed corners plotted against the temperature gradient of the slab.
These slab corners were not directly trafficked but the rocking motion of the unrestrained slabs
caused substantial deflection at these slab corners with the corner at JDMD 6 having deflections
as high as 0.8 mm.
Stage 5 Distribution
UCPRC- RR- 2006- 10
66
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
- 0.8 - 0.6 - 0.4 - 0.2 0 0.2 0.4 0.6 0.8
Temperature gradient ( oC/ cm)
Deflection ( mm)
JDMD 1
JDMD 2
JDMD 4
JDMD 5
Figure 72. Resilient vertical deflection of the shaded slab corners for the ungrouted test,
597FDUG.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
- 0.8 - 0.6 - 0.4 - 0.2 0 0.2 0.4 0.6 0.8
Temperature gradient ( oC/ cm)
Deflection ( mm)
JDMD 6
JDMD 7
Figure 73. Resilient vertical deflection of the exposed slab corners for the ungrouted test,
597FDUG.
Stage 5 Distribution
UCPRC- RR- 2006- 10
67
Figure 74 shows the resilient vertical mid- slab edge deflection plotted against the
temperature gradient of the slab. The trafficked mid- slab edge at JDMD 3 had a significantly
higher resilient deflection than the untrafficked edge at JDMD 10 with no load transfer to the far
edge of the untrafficked slab ( JDMD 10). The mid- slab edge deflection does not seem to be
correlated to the temperature gradient of the slab but the temperature gradient range was small
because the trafficked edge of the slab was shielded by the HVS.
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
- 0.8 - 0.6 - 0.4 - 0.2 0 0.2 0.4 0.6 0.8
Temperature gradient ( oC/ cm)
Deflection ( mm)
JDMD 3
JDMD 10
Figure 74. Resilient vertical deflection of the slab mid- slab edge for the ungrouted test.
597FDUG.
Figure 75 shows the resilient transverse joint horizontal deformation activity plotted
against the surface temperature, and Figure 76 shows the resilient longitudinal joint horizontal
joint activity plotted against the surface temperature for the joint between the two rows of slabs
( H15 and H16) and the joint between the trafficked slabs and the AC shoulder [ H15( a) and
H16( a)].
Stage 5 Distribution
UCPRC- RR- 2006- 10
68
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
15 20 25 30 35 40 45
Surface temperature ( oC)
Joint resilient activity ( mm)
H 13
H 14
Figure 75. Resilient transverse joint activity for the ungrouted test, 597FDUG.
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
15 20 25 30 35 40 45
Surface temperature ( oC)
Joint resilient activity ( mm)
H 15
H 15a
H 16
H 16a
Figure 76. Resilient longitudinal joint activity for the ungrouted test, 597FDUG.
In summary the following observations are made regarding the ungrouted load test,
597FDUG:
• Thermal curl response:
Stage 5 Distribution
UCPRC- RR- 2006- 10
69
o The slab corner at JDMD 4 was shaded by the HVS and had a total
thermal curl movement of only 0.5 mm for a temperature gradient range
from - 0.2 to + 0.2° C/ cm ( temperature differential top to bottom
of - 4 to + 4° C). The slab corner at JDMD 4 seems to be very stiff in terms
of thermal curl response.
o The slab corner at JDMD 6 was exposed and had a total thermal curl
movement of 1.6 mm for a temperature gradient range from - 0.2 to
+ 0.8° C/ cm ( temperature differential of - 4 to + 18° C).
o The transverse joints at H13 and H14 had total thermal curl joint activity
of 0.3 mm over a temperature range of 17 to 24° C.
o The longitudinal joint between the slab and the AC shoulder had a total
thermal curl joint activity of 0.2 mm over a temperature range of 17 to
24° C.
o The longitudinal joint at H15 had a total thermal curl joint activity of
0.9 mm over a temperature range of 17 to 42° C.
• Resilient deflection response:
o The temperature gradient range on the trafficked portion of the test
section was limited to a range between - 0.2 and + 0.2° C/ cm because of
the shading effect of the HVS. Within this temperature gradient range,
the slab corner at JDMD 4 had the lowest resilient deflection of between
0.2 and 0.4 mm. Again, the slab corner at JDMD 4 seems to be stiff
compared to the other slab corners. The slab corner at JDMD 5 adjacent
to JDMD 4 had a resilient deflection between 0.6 and 1.0 mm. The slab
corners at the other end of the test section ( JDMDs 1 and 2) had the
highest deflections, between 0.8 and 1.6 mm.
o The exposed slab corners at JDMDs 6 and 7 had a wider temperature
gradient range from about - 0.2 to + 0.8 ° C/ cm ( temperature differential of -
4 to + 18° C). The resilient deflections ranged between 0.4 and 0.8 mm for
this temperature gradient range but these corners were not trafficked and
the deflection is the result of the rocking of the unrestrained slabs.
o The resilient mid- slab edge deflection at JDMD 3 ranged betw