Consideration of Preservation in Pavement Design and Analysis Procedures (2015)

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10 C H A P T E R 3 LTPP Test Sections Because of the age of the LTPP and other test sections used in the development and calibration of the MEPDG performance prediction models, it has been suggested that preservation treatments may have been applied to these sections such that the developed models already reflect the effects of preservation. To determine whether preservation treatments were indeed applied to these sections and if their effects were accounted for in the performance data, the development of MEPDG predic- tion models for (a) transverse thermal cracking, fatigue crack- ing, rutting, and smoothness of both new/reconstructed flexible pavements and HMA overlays and (b) transverse slab cracking, joint faulting, punchouts (continuously reinforced concrete [CRC] pavement), and smoothness for new/reconstructed rigid pavements, restored jointed plain concrete (JPC) pavements, and JPC and CRC overlays was investigated. The various sections used in the development and calibra- tion of flexible and rigid pavement performance prediction models were identified along with the range of years in which performance data were used in the modeling. Maintenance history information for these sections was then extracted from the LTPP and other databases and summarized to provide an overview of the types of maintenance treatments applied, dates of application, and whether the treatments may have affected the pavement performance trends and consequently the MEPDG models. Table 2 lists the LTPP experiments that include sections of relevance to this evaluation. MEPDG Consideration of Preservation This section describes the LTPP and other pavement test sections that were used in developing and calibrating the var- ious MEPDG performance prediction models. It also identi- fies those sections that received a preservation treatment and indicates whether the effects of preservation treatments are reflected in the performance data that were used. Appendix H provides information on LTPP sections used in the develop- ment and calibration of the MEPDG models, including the date of construction (or rehabilitation) and the date of inclu- sion in the LTPP program, the type of applied maintenance treatment (if any), and if there was consideration of preserva- tion treatments effects. Table 3 lists the number of LTPP (gen- eral pavement studies [GPS] and specific pavement studies [SPS]) and other test sections used in the development and calibration of the various MEPDG performance prediction models (ARA, Inc. 2004). Table 4 lists the total number of LTPP sections used in developing/calibrating the models, the number of sections to which some form of preservation was applied during the time period considered in developing/calibrating the models, and the percentage of sections in which the effects of preservation were considered in the data used in developing/calibrating each model. No information was available regarding the time range for the data used to develop or calibrate the models for thermal cracking and smoothness for new/reconstructed flex- ible pavements and HMA overlays, transverse cracking and joint faulting for restored JPC pavements and unbonded JPC overlays, and punchouts for bonded PCC overlays over CRC pavements. Table 4 shows that preservation treatments have been applied to about 22% of the flexible pavement sections (new/reconstructed and HMA overlays combined) used in developing/calibrating the flexible pavement models. For new/reconstructed rigid pavement models, about 9% of the sections included preservation; no data were available for restored PCC and PCC overlays. The most common types of preservation treatments that might have affected performance data of flexible pavements were crack sealing, fog seals, slurry seals, and seal coats. For rigid pavements, joint resealing (including longitudinal joints in both JPC and CRC), crack sealing, partial-depth repair, and full-depth repair may have affected performance data Assessment of Consideration of Preservation in MEPDG Models

11 (a few instances of diamond grinding and grooving were also recorded in the LTPP database). Review of the LTPP database revealed that the only recorded preservation treatments (and other maintenance and light rehabilitation) were those applied to a pavement section after it was included in the LTPP database. That is, preservation treatments that may have been applied to some GPS sections before the start of LTPP were not recorded. Hence, the number of preservation-treated sections used in developing/calibrating the different MEPDG models is likely larger than what is listed in Table 4. MEPDG Design Approach The design approach used in the MEPDG as illustrated in Figure 4 (AASHTO 2008) includes three stages. The evaluation stage (Stage 1) includes the collection, evaluation, or estima- tion of input data (e.g., foundation support, material charac- terization, traffic, and climate). The analysis stage (Stage 2) includes the evaluation of selected pavement design strategies using pavement response models (based on calculated stresses, strains, and deflections) and distress transfer functions for estimating pavement distresses. The strategy selection stage (Stage 3) occurs outside of the MEPDG and deals with consid- erations unrelated to thickness design, such as construction, policy issues, and life-cycle cost analysis (LCCA). Preservation can be addressed in the design/analysis pro- cess either as part of the analysis stage (Stage 2) or the strategy selection stage (Stage 3). In this latter case, LCCA will iden- tify the cost and performance effects of pavement preserva- tion treatments. This chapter describes three approaches for considering preservation in the analysis stage. One approach requires the development of pavement preservation response models and distress transfer functions. Another approach requires the calibration of MEPDG models using pavement preservation performance data. The third approach accounts for the effects of preservation by adjusting pavement distress and modifying material properties used as inputs in MEPDG Experiment ID Experiment Title GENERAL PAVEMENT STUDIES (GPS) GPS-1 Asphalt Concrete (AC) Pavement on Granular Base GPS-2 AC Pavement on Bound Base GPS-3 Jointed Plain Concrete (JPC) Pavement GPS-4 Jointed Reinforced Concrete (JRC) Pavement GPS-5 Continuously Reinforced Concrete (CRC) Pavement GPS-6A Existing AC Overlay of AC Pavement (existing at the start of the program) GPS-6B AC Overlay Using Conventional Asphalt of AC Pavement – No Milling GPS-6C AC Overlay Using Modified Asphalt of AC Pavement – No Milling GPS-6D AC Overlay on Previously Overlaid AC Pavement Using Conventional Asphalt GPS-6S AC Overlay of Milled AC Pavement Using Conventional or Modified Asphalt GPS-7A Existing AC Overlay on PCC Pavement GPS-7B AC Overlay Using Conventional Asphalt on PCC Pavement GPS-7C AC Overlay Using Modified Asphalt on PCC Pavement GPS-7D AC Overlay on Previously Overlaid PCC Pavement Using Conventional Asphalt GPS-7F AC Overlay Using Conventional or Modified Asphalt on Fractured PCC Pavement GPS-7R Concrete Pavement Restoration Treatments with No Overlay GPS-7S Second AC Overlay, Which Includes Milling or Geotextile Application, on PCC Pavement with Previous AC Overlay GPS-9 Unbonded PCC Overlay on PCC Pavement SPECIFIC PAVEMENT STUDIES (SPS) SPS-1 Strategic Study of Structural Factors for Flexible Pavements SPS-2 Strategic Study of Structural Factors for Rigid Pavements SPS-3 Preventive Maintenance Effectiveness of Flexible Pavements SPS-4 Preventive Maintenance Effectiveness of Rigid Pavements SPS-5 Rehabilitation of AC Pavements SPS-6 Rehabilitation of JPC Pavements SPS-7 Bonded PCC Overlays of Concrete Pavements SPS-8 Study of Environmental Effects in the Absence of Heavy Loads SPS-9P Validation and Refinements of Superpave Asphalt Specifications and Mix Design Process SPS-9A Superpave Asphalt Binder Study Table 2. GPS and SPS experiments with possible data for MEPDG development.

12 models. Availability of data to support the development of these approaches is described in the following sections. Evaluation of Data Availability An assessment of the availability of the data required for considering preservation in the MEPDG was made by (1) iden- tifying the required data elements, (2) determining availability of the required data elements, and (3) assessing the appro- priateness of available data. Because pavement preservation is more commonly used for flexible pavements, this assessment Pavement Model Experiment Type Number of LTPP Sections GPS SPS Total FLEXIBLE PAVEMENTS Fatigue Cracking1 Model—New/Reconstructed Flexible Pavements GPS-6B, SPS-1 79 16 95 Fatigue Cracking1 Model—HMA Overlay over Flexible Pavements GPS-6B, SPS-5 13 33 46 Fatigue Cracking1 Model—HMA Overlay over Fractured Slab Pavements SPS-6 0 3 3 Fatigue Cracking1 Model—HMA Overlay over JPC Pavements GPS-7B, SPS-6 4 3 7 Thermal Cracking Model—New/Reconstructed Flexible Pavements2 GPS-1 22 0 22 Rutting Model—New/Reconstructed Flexible Pavements GPS-1, GPS-2, SPS-1 79 16 95 Rutting Model—HMA Overlay over Flexible Pavements GPS-6B, SPS-5 14 32 46 Rutting Model—HMA Overlay over Fractured Slab Pavements SPS-6 0 3 3 Rutting Model—HMA Overlay over JPC Pavements GPS-7B, SPS-6 4 3 7 Smoothness Model—New/Reconstructed Flexible Pavements and HMA Overlays GPS-1, GPS-2, GPS-6, GPS-7 N/A N/A N/A RIGID PAVEMENTS Punchout Model—New/Reconstructed CRC3 GPS-5 43 0 43 Transverse Joint Faulting Model— New/Reconstructed JPC4 GPS-3, SPS-2 64 83 147 Transverse Cracking Model—New/Reconstructed JPC5 GPS-3, SPS-2 63 84 147 Transverse Joint Faulting and Cracking Models— Restored JPC6 SPS-6 0 8 8 Transverse Joint Faulting and Cracking Models— Unbonded JPC Overlays GPS-9 16 0 16 Punchout Model—Unbonded CRC Overlays7 GPS-9 2 0 2 Punchout Model—Bonded PCC Overlay over CRC SPS-7 0 4 4 Smoothness Model—New/Reconstructed JPC GPS-3 78 0 78 Smoothness Model—New/Reconstructed CRC GPS-5 45 0 45 Notes: 1 Bottom-up alligator and top-down longitudinal cracking. 2 Also includes non-LTPP sections from the MnROAD study. 3 Also includes 17 non-LTPP sections from Illinois (I-80 and I-94 in Cook County and U.S. 40 in Fayette County). 4 Also includes 110 non-LTPP sections in nine states from the FHWA Rigid Pavement Performance and Rehabilitation study (RIPPER). 5 Also includes 13 non-LTPP sections in seven states from the FHWA Rigid Pavement Performance and Rehabilitation study. 6 Also includes 15 non-LTPP sections from the ACPA Diamond Grinding Study and NCHRP Project 10-41 study. 7 Also includes six non-LTPP sections in four states from the NCHRP Project 10-41 study. N/A = not available. Table 3. LTPP test sections used in MEPDG model development and calibration (ARA, Inc. 2004). focused on flexible pavement preservation. Design, preserva- tion, and pavement management practices and experiences of the 14 interviewed SHAs indicated that eight states (Arizona, Indiana, Kansas, Minnesota, Missouri, North Carolina, Texas, and Washington) may have the types of data required for implementing this approach; the data available from these states were evaluated. (Appendix I provides details.) The consideration of preservation effects requires design analysis of a baseline/untreated pavement structure and a corresponding preservation-treated pavement structure using the AASHTOWare Pavement ME Design software. Therefore,

13 MEPDG Performance Model Number of Test Sections Percent Test Sections with Preservation Effects Considered in Performance Data Preservation Effects Considered in Performance Data Preservation Effects Not Considered in Performance Data Effects Unknown Total FLEXIBLE PAVEMENTS Fatigue Cracking1 Model—New/ Reconstructed Flexible Pavements 20 63 12 95 21 Fatigue Cracking1 Model—HMA Overlays over Flexible Pavements 1 45 0 46 2 Fatigue Cracking1 Model—HMA Overlays over Fractured Slab Pavements 2 1 0 3 67 Fatigue Cracking1 Model—HMA Overlays over JPC Pavements 5 7 0 12 42 Thermal Cracking Model—New/ Reconstructed Flexible Pavements N/A N/A N/A N/A N/A Rutting Model—New/Reconstructed Flexible Pavements 14 74 7 95 15 Rutting Model—HMA Overlays over Flexible Pavements 21 25 0 46 46 Rutting Model—HMA Overlays over Fractured Slab Pavements 2 1 0 3 67 Rutting Model—HMA Overlays over JPC Pavements 4 3 0 7 57 Smoothness Model—New/ Reconstructed Flexible Pavements and HMA Overlays N/A N/A N/A N/A N/A RIGID PAVEMENTS Punchout Model—New/Reconstructed CRC 10 31 2 43 23 Transverse Joint Faulting Model— New/Reconstructed JPC 10 122 15 147 7 Transverse Cracking Model— New/Reconstructed JPC 12 123 12 147 8 Transverse Joint Faulting and Cracking Models—Restored JPC N/A N/A N/A N/A N/A Transverse Joint Faulting and Cracking Models—Unbonded JPC Overlays N/A N/A N/A N/A N/A Punchout Model—Unbonded CRC Overlays N/A N/A N/A N/A N/A Punchout Model—Bonded PCC Overlay over CRC N/A N/A N/A N/A N/A Smoothness Model—New/ Reconstructed JPC 7 68 3 78 9 Smoothness Model—New/ Reconstructed CRC 3 41 1 45 7 Notes: 1 Bottom-up alligator and top-down longitudinal cracking. N/A = not available. Table 4. Consideration of preservation in LTPP test sections.

14 input data required for this analysis, such as design properties and analysis parameters, traffic and climate characteristics, structure properties, material layer properties, and foundation and bedrock properties, must be established. A complete list- ing of required inputs is available in several sources (AASHTO 2008, the AASHTOWare Pavement ME Design software and Software Help System, and FHWA 2010). Table 5 lists the data elements required for the design analysis of untreated and preservation-treated pavement structures. Sources of Required Data Elements: Required data are likely to be available from different sources. Data on pavement condi- tion when a preservation treatment is applied may be obtained from pavement management data or from the guidelines for preservation treatment application, and preservation treatment material properties data may be obtained from actual histori- cal materials test data. As-built records will provide pavement structure data, and actual historical materials test data or sam- pling and testing will provide data on existing HMA surface material properties. Existing pavement moisture and thermal profile data may be derived from instrumented test sections, and data on immediate post-treatment distress/smoothness will likely be available from pavement management data. Availability of the Required Data: Because efforts to evalu- ate preservation treatment performance and to evaluate, cali- brate, implement, or use the MEPDG would require the types of data elements considered in this assessment, relevant states’ efforts were identified. The availability of a pavement manage- ment program and system database, a construction/materials New Pavement Design and Analyses Rehabilitation Design and Analyses Climate/Environment Analysis Temperature and Moisture Traffic Analysis Truck Classification and Volume; Axle Load Distribution; Forecasting New Materials Analysis Hot Mix Asphalt Portland Cement Concrete Cementitous Materials Unbound Granular Materials Soils/Embankment Materials Inputs for Design Site Investigations Borings and Field Testing; Soils Testing in Laboratory; Drainage; Volume Change; Frost Heave Paving Materials Select Trial Pavement Design Strategies Pavement Evaluation Distress Surveys; Nondestructive Testing; Ride Quality Testing; Borings & Cores; Materials Testing Design Criteria Design Criteria Pavement Response Model Calculate Stresses, Strains, Deflections Calculate Incremental Damage Distress Transfer Functions and Pavement Distress Models Reliability Analysis Has Design Criteria Been Meet? NO YES Viable Design Alternative Life-Cycle Cost Analysis Engineering and Constructability Analysis Select Strategy STAGE 3 – STRATEGY SELECTION Policy Issues and Decisions Modify Design Features or Materials Rehabilitation/Repair Materials Roughness; IRI Distortion; Rutting Faulting Load Related Cracking Non-Load Related Cracking STAGE 1 - EVALUATION STAGE 2 - ANALYSIS Note: IRI = International Roughness Index. Figure 4. MEPDG conceptual analysis process (AASHTO 2008).

15 Table 5. Data elements required for AASHTOWare Pavement ME Design analysis. Data Category Data Element Analysis Parameters Typical designs of untreated pavement structure. Preservation-treated pavement structure. Design life. Design reliability (for individual distresses and smoothness). Performance indicators (e.g., rutting, transverse cracking, bottom-up alligator cracking, top-down longitudinal cracking, reflective cracking, and IRI). Pavement/treatment failure thresholds (corresponding to the application of a rehabilitation treatment or a follow-up preservation treatment). Structure Properties Untreated design strategy (layer types, materials, and thicknesses). Preservation-treated design strategy (layer types, materials, and thicknesses). Surface shortwave absorptivity. Preservation Treatment Application Parameters Treatment timing corresponding to either the optimal timing identified using OPTime or to an agency-specified timing value. – Distress, smoothness, and/or overall condition levels of original pavement at time of treatment application. Treatment material properties. – Engineering and thermal properties (e.g., Poisson’s ratio, dynamic modulus, tensile strength, creep compliance, thermal conductivity, heat capacity, surface shortwave absorptivity, coefficient of thermal contraction). – Volumetric properties (e.g., air voids, effective asphalt content, voids filled with asphalt, mix density, asphalt binder grade/viscosity. Effect of treatment on existing pavement structure (e.g., removal depth of existing HMA surface [milling], treatment application thickness, layer interface condition [degree of bond between treatment and existing HMA surface]). Effect of treatment (short- and long-term) on existing HMA surface layer material properties. – Engineering and thermal properties (same as above). – Volumetric properties (same as above). Effect of treatment (short- and long-term) on moisture and thermal profile of existing pavement. – Drainage/infiltration potential, cross-slope and drainage path length, surface shortwave absorptivity. Performance Modeling Parameters Immediate adjustment of post-treatment performance levels. – Post-treatment distress/smoothness measurements. Long-term adjustment of post-treatment distress level via rate of redevelopment of distresses/smoothness. – Reflection cracking (of fatigue and thermal cracks in existing flexible pavement)—data for defining a and b model parameters (essentially treatment thickness) and data for defining d model parameter, which governs the acceleration (d > 1) or delay (d < 1) in the formation of reflective cracks. Note: IRI = International Roughness Index. • • • • • • • • • • • • • • • • database, and any type of MEPDG design/materials database was then determined. A suitability rating was assigned to each state for each approach; the results were used to select five states (Indiana, Minnesota, Missouri, North Carolina, and Texas) for a detailed investigation of data availability. An elec- tronic survey of these states was then conducted to identify the data that could be used to develop the proposed approaches; the responses were compiled and summarized. (Details are provided in Appendix G.) Appropriateness of Available Data: The information obtained regarding the availability and reliability of data was evaluated for each of the key data elements. A score of 1 through 5 was assigned for each element, with a score of 1 denoting a lack of data to support the development of the proposed approach and a score of 5 denoting good overall availability of useful data. (Details are provided in Appendix G.) The overall scores indicated that the development and validation of approaches for incorporating preservation in the MEPDG process are not currently feasible. As a result, the research was focused on pre- paring detailed processes for three approaches and illustrat- ing processes for their implementation. These processes are described in the following chapters.