Incorporating Slab/Underlying Layer Interaction into the Concrete Pavement Analysis Procedures (2017)

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Inco ACKNOWLED This work was with the Feder which is admin Medicine. COPYRIGHT I Authors herein persons who o Cooperative R purposes. Per FMCSA, FRA, product, metho uses will give a request permis DISCLAIMER The opinions a are not necess or the program The informatio edited by TRB rporati Con GMENT sponsored by t al Highway Adm istered by the T NFORMATION are responsibl wn the copyrigh esearch Progra mission is give FTA, Office of d, or practice. ppropriate ack sion from CRP nd conclusions arily those of th sponsors. n contained in t . W ng Slab crete P L he American As inistration, and ransportation R e for the authen t to any previo ms (CRP) gran n with the unde the Assistant Se It is expected th nowledgment o . expressed or im e Transportatio his document w NC eb-Only /Under aveme . Khazanov Univers Minn sociation of St was conducted esearch Board ticity of their m usly published o ts permission to rstanding that n cretary for Res at those reprod f the source of a plied in this re n Research Bo as taken direct HR Docume lying La nt Analy ich and D. T ity of Minnes eapolis, MN ate Highway an in the Nationa (TRB) of the N aterials and for r copyrighted m reproduce ma one of the mate earch and Tec ucing the mate ny reprinted or port are those o ard; the Nation ly from the subm P nt 236: yer Inte sis Pro ompkins ota Contracto d Transportatio l Cooperative H ational Academ obtaining writte aterial used he terial in this pub rial will be used hnology, PHMS rial in this docu reproduced ma f the researche al Academies o ission of the a raction cedure r’s Final Repor n Officials (AAS ighway Resea ies of Science n permissions f rein. lication for clas to imply TRB, A, or TDC endo ment for educat terial. For oth rs who perform f Sciences, Eng uthor(s). This m into th s t for NCHRP Pr Submitted Feb HTO), in coop rch Program (N s, Engineering, rom publishers sroom and not AASHTO, FAA rsement of a p ional and not-fo er uses of the m ed the researc ineering, and M aterial has not e oject 01-51 ruary 2017 eration CHRP), and or -for-profit , FHWA, articular r-profit aterial, h. They edicine; been

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i CONTENTS CHAPTER 1  BACKGROUND ............................................................................................................................. 1  1.1  PROBLEM STATEMENT ........................................................................................................................................... 1  1.2  RESEARCH SCOPE ................................................................................................................................................. 1  CHAPTER 2  RESEARCH APPROACH ................................................................................................................. 2  2.1  INTRODUCTION .................................................................................................................................................... 2  2.2  ASSESSMENT OF SLAB‐BASE INTERACTION STUDIES ...................................................................................................... 3  2.2.1  Laboratory studies on slab‐base interaction .......................................................................................... 3  2.2.2  Observations of slab‐base interaction using full‐scale pavement data ................................................. 4  2.3  EFFECT OF SLAB‐BASE INTERACTION ON IN‐FIELD PAVEMENT PERFORMANCE ..................................................................... 5  2.3.1  Effect of base type on pavement performance ...................................................................................... 6  2.3.2  Base layer effect on pavement deflections ............................................................................................ 7  2.4  EVALUATION OF MODELS FOR SLAB‐BASE INTERACTION AND PAVEMENT PERFORMANCE ..................................................... 8  2.4.1  Mechanical models for slab‐base bending............................................................................................. 8  2.4.2  AASHTO M‐E procedure and slab‐base interaction ............................................................................... 9  2.5  RESEARCH METHODOLOGY ................................................................................................................................... 21  2.5.1  Characterization of slab‐base interaction ............................................................................................ 21  2.5.2  Development of alternative models for pavement performance ......................................................... 26  2.5.3  Implementation of alternative models for the AASHTO M‐E procedure ..............................................40  CHAPTER 3  FINDINGS AND APPLICATIONS .................................................................................................... 42  3.1  CHARACTERIZATION OF SLAB‐BASE INTERACTION ...................................................................................................... 42  3.1.1  Base layer effect on the composite k‐value ......................................................................................... 42  3.1.2  Effective flexural stiffness under partially bonded slab‐base interface ............................................... 43  3.1.3  Built‐in curl analysis ............................................................................................................................. 46  3.2  ALTERNATIVE PERFORMANCE MODELS TO ACCOUNT FOR SLAB‐BASE INTERACTION ...........................................................48  3.2.1  Transverse cracking model .................................................................................................................. 49  3.2.2  Joint faulting model ............................................................................................................................. 55  3.2.3  Punchout model ................................................................................................................................... 58  3.3  IMPLEMENTATION OF ALTERNATIVE MODELS FOR THE AASHTO M‐E PROCEDURE .......................................................... 61  3.3.1  Alternative JPCP transverse cracking model ........................................................................................ 61  3.3.2  Alternative JPCP joint faulting model .................................................................................................. 62  3.3.3  Companion to the AASHTO M‐E software ........................................................................................... 63  3.4  APPLICATION OF ALTERNATIVE MODELS TO AASHTO M‐E PROJECTS ........................................................................... 66  CHAPTER 4  SUMMARY AND RECOMMENDATIONS FOR FUTURE RESEARCH ...................................................69  4.1  SUMMARY ........................................................................................................................................................ 69  4.2  RECOMMENDATIONS FOR FUTURE RESEARCH ........................................................................................................... 69  REFERENCES ...................................................................................................................................................... 71  APPENDIX A. SUMMARY OF LTPP SECTIONS USED TO CALIBRATE ALTERNATIVE MODELS  APPENDIX B. DEVELOPMENT OF ALTERNATIVE JPCP CRACKING MODEL TO INCORPORATE SLAB‐BASE EFFECTS  APPENDIX C. USER’S GUIDE TO SOFTWARE FOR MODIFIED MODELS  APPENDIX D. ANALYSIS OF CENTER AND EDGE LOADED FALLING WEIGHT DEFLECTOMETER DATA  APPENDIX E. ANALYSIS OF PROFILE DATA USING EMPIRICAL MODE DECOMPOSITION  APPENDIX F. ANALYSIS OF FALLING WEIGHT DEFLECTOMETER DATA TO CHARACTERIZE SLAB‐BASE INTERACTION 

ii LIST OF TABLES Table 1. Design moduli of subgrade reaction for pavements with untreated and treated base layers [from Packard (1984)] .......................................................................................................... 2  Table 2. Assessment of available friction models .......................................................................... 8  Table 3. Consideration of relevant items in the original and modified JPCP transverse cracking procedures ..................................................................................................................................... 27  Table 4. Example of frequency distribution of probability of a given combination of TL and TNL for a given hour of a specific calendar month ............................................................................... 32  Table 5. Example of frequency distribution of total frequencies from Table 4 with respect to TNLa .............................................................................................................................................. 32  Table 6. AASHTO recommendations for base friction coefficient in CRCP project design [reproduced from AASHTO (2008)] ............................................................................................ 39  Table 7. Backcalculated subgrade k-values for LCB and PSAB base type (normalized to AGG base parameters) for center and edge locations ............................................................................ 43  Table 8. Comparison of backcalculated slab-to-base moduli ratio with recommendations from Khazanovich et al (1997) .............................................................................................................. 44  Table 9. Average slab curling profile standard deviation (in inches) by base type, slab width, and slab thickness ................................................................................................................................ 46  Table 10. Global calibration coefficients for alternative JPCP faulting model ............................ 55  Table 11. Statistics for CTB and PSAB calibration sections from the LTPP GPS-5 experiment 59 

iii LIST OF FIGURES Figure 1. Effective loss of bond slab-base interface after less than two load cycles [from Li et al, (2013)]............................................................................................................................................. 4  Figure 2. (a) Transverse cracking and (b) longitudinal cracking in SPS-2 sections by base type .. 7  Figure 3. Structural model for rigid pavement structural response computations ........................ 10  Figure 4. Effect of base stiffness on seasonal variation in calculated k-value using the AASHTO M-E procedure .............................................................................................................................. 11  Figure 5. Sensitivity of LTPP project 04-0213 to slab support conditions and built-in curl parameter T ................................................................................................................................. 12  Figure 6. Effect of default slab support (T = -10F) on AASTHO M-E response modeling and predicted performance .................................................................................................................. 14  Figure 7. AASHTO M-E cracking predictions for four projects with varied base stiffness and loss of friction ............................................................................................................................... 16  Figure 8. Cracking performance of structurally equivalent JPCP projects in the AASHTO M-E procedure ....................................................................................................................................... 16  Figure 9. AASTHO M-E faulting predicted performance relative to observed faulting for LTPP calibration sections by base type ................................................................................................... 18  Figure 10. AASTHO M-E predicted punchouts relative to observed punchouts for LTPP calibration sections by base type ................................................................................................... 20  Figure 11. Meshes and load locations for (a) center- and egde-loading simulations in the developed backcalculation procedure ........................................................................................... 21  Figure 12. Transformed section concept (from Khazanovich and Gotlif 2002) ........................... 24  Figure 13. (a) Raw profilometer data and (b) EMD-decomposed signal resembling slab curling from three passes of profilometer on March 30, 1994 on LTPP 37-0201 .................................... 26  Figure 14. Critical load and stress locations for bottom-up cracking (at left) and top-down cracking (at right) [from ARA (2004)] ......................................................................................... 30  Figure 15. Predicted performance vs. measured performance for LTPP sections with (a) CTB and (b) PSAB for all five erodibility indices ....................................................................................... 36  Figure 16. Comparison of predicted faulting from the unmodified, recreated model and the AASHTO M-E model for LTPP GPS-3 and SPS-2 projects ........................................................ 37  Figure 17. Sensitivity of joint faulting to Base LTE in undoweled AASHTO M-E calibration projects .......................................................................................................................................... 38  Figure 18. Sensitivity of GPS-5 aggregate base projects to base friction parameter, f ................. 40  Figure 19. (a) Well-behaved and (b) erratic inferred friction performance over time in LTPP Section 3-3023 .............................................................................................................................. 45  Figure 20. Effect of slab profile on increase in IRI by base type for sections with (a) 12-foot and (b) 14-foot lane widths .................................................................................................................. 47  Figure 21. Slab profiles given EMD analysis of two profilometer passes on LTPP Section 37- 0201............................................................................................................................................... 47  Figure 22. Modified JPCP transverse cracking model predictions compared to LTPP observations by project base type using developed calibration coefficients ................................ 50  Figure 23. Influence of base stiffness on sensitivity to loss of friction in predicted cracking performance in the modified cracking model ............................................................................... 51  Figure 24. Cracking performance of structurally equivalent JPCP projects in the modified cracking model .............................................................................................................................. 52 

iv Figure 25. Performance of LTPP section 04-0219 with different levels of initial friction (T = - 10, A = 6, a = 2.5) ......................................................................................................................... 53  Figure 26. Performance of LTPP section 04-0219 with different values of characteristic length, a, used in strength criterion (T = -10, A = 4, *=0.001) ................................................................ 54  Figure 27. Performance of LTPP section 04-0219 with different values of calibration coefficient A for built-in curl parameter, T (T = -10, *=0.001, a = 2.5) .................................................. 54  Figure 28. Sensitivity of joint faulting to Base LTE varied values of T for AASHTO M-E calibration projects with (a) cement-treated bases and (b) partially stabilized asphalt bases ....... 56  Figure 29. Modified JPCP faulting model predictions by project base type compared to LTPP observations in AASHTO calibration database ............................................................................ 57  Figure 30. Comparison of faulting performance between the current AASHTO M-E and alternative model for LTPP sections with (a) CTB and (b) PSAB base types ............................. 58  Figure 31. Predicted CRCP punchouts compared to LTPP observation ...................................... 60  Figure 32. Comparison of punchout performance between the current AASHTO M-E and alternative model for LTPP sections with (a) CTB and (b) PSAB base types ............................. 61  Figure 33. User interface for alternative models (red numbers added to indicate user inputs) .... 63  Figure 34. Selecting an existing AASHTO project directory in the interface software for the alternative models ......................................................................................................................... 64  Figure 35. An example of monthly non-dimensional friction parameter input file ..................... 65  Figure 36. Selecting user-provided nondimentional friction data ............................................... 65  Figure 37. Results of the alternative faulting model opened with (a) Notepad and (b) Excel ...... 66  Figure 38. Cracking observations and predicted performance according to (a) AASHTO M-E and (b) alternative model for LTPP Section 4-0217 ............................................................................ 67  Figure 39. LTPP 4-0217 performance prediction given user-defined friction data ...................... 68 

v ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 01-51 by the Department of Civil, Environmental, and Geo-Engineering at the University of Minnesota (UMN). UMN was the contractor for this study, with the Special Projects Administration (SPA) at UMN serving as Fiscal Administrator. Dr. Lev Khazanovich, Professor of Civil Engineering at UMN, was the Project Director and Principal Investigator. The other author of this report is Dr. Derek Tompkins, Research Associate at UMN. The work was done under the general supervision of Prof. Khazanovich at UMN and included the participation of undergraduate and graduate students in the Department of Civil, Environmental, and Geo- Engineering at the University of Minnesota. The authors thank Drs. Alex Gotlif and Greg Larson at Applied Research Associates, Inc., for their insight into the AASHTO M-E models. The authors also acknowledge the provision of data to the project by Prof. Julie Vandenbossche, Associate Professor of Civil Engineering at the University of Pittsburgh, and thank her for her willingness to answer questions about the data.

vi SUMMARY The research project investigated the interaction between the concrete slab and base layer in jointed plain concrete pavements (JPCP) and continuously reinforced concrete pavements (CRCP). The research study performed the following: 1. Reviewed literature characterizing the interaction between the slab and base layer; 2. Identified factors that influence slab-base behavior and pavement performance using full-scale pavement data and analysis methods; 3. Evaluated the AASHTO mechanistic-empirical (M-E) models for JPCP and CRCP performance and structural friction models for slab-base interaction; and 4. Investigated alternative models and modifications for the AASHTO M-E procedure to better account for the effects of slab-base interaction on pavement performance. As a result of this approach, the project developed alternative M-E performance models to account for slab-base interaction that are fully compatible with the AASHTO M-E framework. Slab-base interaction in experimental and in-situ pavements Data from in-situ and experimental pavement were used to characterize slab-base interaction and identify factors that influence it as well as pavement performance. The dataset included the SPS- 2, GPS-3, and GPS-5 experiments in the Long-Term Pavement Performance (LTPP) database, specifically profilometer, falling weight deflectometer, and pavement performance data. New analysis tools were produced to interpret the data. As a result of this analysis, it was found that slab-base interaction is influenced by many variables within the pavement system and cannot be described by a single parameter. Evaluating the AASHTO M-E procedure The effect of slab-base interaction in the AASHTO M-E procedure performance models was fully evaluated. The study identified critical parameters influenced by slab-base interaction in the JPCP transverse cracking mode, the JPCP joint faulting model, and the CRCP punchout model. The sensitivity of these models to parameters related to slab-base interaction was evaluated using a database of LTPP projects. Development of M-E distress prediction models to account for slab-base interaction Alternative M-E performance models were developed to better account for the interaction between the slab and the base layer. A major revision of the JPCP transverse cracking model was proposed. This includes the incorporation of a partial bond model for slab-base interaction and the modification of the effects of temperature in the pavement system, including the characterization of built-in curling. The JPCP faulting model was modified through adjustment of the load transfer coefficients and built-in curling for stabilized bases. The recommended base friction coefficients for the CRCP punchout model were also revised. The alternative models were calibrated using the AASHTO M-E calibration database. These models are fully compatible with the AASHTO M-E framework and thus can be incorporated into the AASHTO M-E procedure and software. Rudimentary software was also developed to implement the alternative models for evaluation and calibration.