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Standard Definitions for Common Types of Pavement Cracking 31 C H A P T E R 4 Cracking Data Desired by State Highway Agencies Introduction Based on the SHA survey results and a comprehensive literature review, this chapter summarizes the cracking data desired by SHAs. Various cracking data applications desired by SHAs include pavement management, HPMS reporting, MEPDG local calibration, MAP-21 or FAST Act, and in support of asset management. Pavement Management As summarized in Chapter 2, the SHA survey specifically included two questions designed to determine what cracking data is needed and how the cracking data is used. The first question focused on the types of cracking data collected by SHAs for various pavement types (asphalt, JPCP, CRCP, and composite pavements). As shown in Figure 14a, almost all SHAs collect transverse, longitudinal, and alligator/fatigue cracking. For asphalt and composite pavements, SHAs typically collect transverse, longitudinal, alligator/fatigue, block, and edge cracking (Figure 14b). For JPCP, transverse, longitudinal, âDâ cracking, corner breaks, and shattered slabs (and others) are typically collected. For CRCP pavements, transverse, longitudinal, âDâ cracking, and shattered slabs (and others) are typically collected. The second question was used to determine the purpose of why the desired cracking data are collected (Figure 15). Transverse cracking, longitudinal cracking, alligator/fatigue cracking, block cracking, edge cracking, âDâ cracking, and corner break are normally collected by SHAs for pavement management. For HPMS reporting, transverse cracking, longitudinal cracking, and alligator/fatigue cracking are normally collected. Fewer SHAs collect cracking data for other purposes, such as Pavement ME Design, failure analysis, or research.
Standard Definitions for Common Types of Pavement Cracking 32 (a) Cracking data collected. (b) Cracking data type vs. pavement type. Figure 14 Cracking data collection for different pavement types. 0% 20% 40% 60% 80% 100% 0% 20% 40% 60% 80% 100% AC PCC CRCP ACÂ overÂ PCC/CRCP
Standard Definitions for Common Types of Pavement Cracking 33 Figure 15 Usage of cracking data. HPMS Reporting The HPMS is a national program that includes inventory information for the nationâs public roads as certified by the statesâ governors annually. All roads open to public travel are reported in HPMS regardless of ownership, including federal, state, county, city, and privately owned roads such as toll facilities (FHWA 2016). The data items to be reported include inventory, route, traffic, geometric, pavement, special networks, and so on. HPMS data are used at the national level for funding distribution, performance measures, highway statistics, condition reporting, FHWAâs transportation planning and policy studies, and other data dissemination media. In particular, cracking percent is required for pavement modeling purposes and pavement condition performance metric rating for the National Highway System (NHS). The cracking percent is defined as the percentage of pavement surface exhibiting cracking as follows (FHWA 2016): ï· Asphalt: Percent of total wheel path area exhibiting visible fatigue type cracking at all severity levels. It is calculated as the total area in both wheel paths where cracks are detected, divided by the total pavement area of the 528 ft. (161 m) reporting section. ï· JPCP: Percent of slabs with transverse cracking. It is calculated as the number of slabs containing one or more transverse cracks extending for at least one-half the lane width, divided by the total number of slabs in the 528 ft. (161 m) reporting section. ï· CRCP: Percent area exhibiting longitudinal cracking, punchouts, and patching. It is determined as the area of pavements where cracking or distresses are detected, divided by the total area of the 528 ft. (161 m) reporting section. The HPMS Field Manual (FHWA 2016) recommends AASHTO R 85 and the LTPP Distress Manual be followed for reporting cracking data. For asphalt pavements, measuring and reporting cracking outside the wheel path areas are not required. Pavement cracking percent is reported to 0% 20% 40% 60% 80% 100% PavementÂ Management HPMS PavementÂ MEÂ Design FailureÂ Analysis Research
Standard Definitions for Common Types of Pavement Cracking 34 the nearest 1%. The percent measured cracking is reported annually for the interstate and biennially for the non-interstate system. The HPMS Field Manual (FHWA 2016) also indicates that both automated and manual surveys for data collection and reporting are acceptable, however, automated methods are preferred for roadways where roughness data is measured. MEPDG Local Calibration The MEPDG and Pavement ME Designâ¢ include models calibrated and validated using data from the LTPP program. The AASHTO Guide for the Local Calibration of the Mechanistic- Empirical Pavement Design advises agencies to validate and calibrate (if needed) the performance prediction models using local field data to achieve more reliable performance predictions (AASHTO 2010). The implementation of mechanistic-empirical pavement analysis and design methodologies is expected to affect pavement management practices and, in particular, pavement condition data collection. The validation and calibration of the mechanistic- empirical models depend on accurate performance data from in-service pavement sections. Although information currently available in some PMS can be used to develop initial calibration factors, an accurate long-term calibration will require significant changes in the information that is stored in the PMS databases (FHWA 2010). The cracking data required for the local calibration of MEPDG models is included in Table 9. The MEPDG considers both structural and functional pavement performance characteristics in its estimation of predicted pavement damage. The cracking data for asphalt pavements for MEPDG includes percent alligator cracking and length of transverse cracking. The cracking data considered for concrete pavements for MEPDG includes percent transverse slab cracking for JPCP, and the number of punchouts for CRCP (AASHTO 2020). The majority of the pavement performance indicators specified in Table 9 are available in a typical pavement management system. However, differences between SHA condition definitions and those identified in the LTPP Distress Manual have been widely reported as one of the major data challenges for local calibration. For instance, the transverse cracking from PMS is used to represent the thermal cracking during local calibration (Darter et al. 2009, FHWA 2010, Ceylan et al. 2013, Darter et al. 2014). However, according to the commonly used cracking protocols, transverse cracking records from PMS do not differentiate between thermal and reflection cracking measurements for composite pavements. Therefore, cracking data definitions specific to the Pavement ME Designâ¢ should be considered during the development of the comparable standard cracking definitions. An accurate long-term calibration will require significant changes and improvements in the definition, collection, processing, and storage of pavement cracking data.
Standard Definitions for Common Types of Pavement Cracking 35 Table 9 Distress Data Desired for MEPDG Local Calibration (AASHTO 2020) HMA Distress Data IRI1 in/mile Alligator cracking % cracked per section length Transverse cracking ft/mile Asphalt rutting2 (permanent deformation) in. JPCP Distress Data IRI1 in/mile Transverse slab cracking % Mean joint faulting2 in. Continuously Reinforced Concrete Pavement (CRCP) Distress Data IRI1 in/mile Number of punchouts per/mile 1 International Roughness Index, typical measured every tenth of a mile 2 Average, standard deviation, COV, maximum, minimum MAP-21 (FAST Act) and Asset Management The 2012 legislation known as âMoving Ahead for Progress in the 21st Century Actâ (MAP-21) and the 2015 âFixing Americaâs Surface Transportation Act (FAST Act)â established a performance-based framework focusing on national transportation goals, and increasing accountability and transparency in how federal highway funds are used. The Acts support the use of performance measures to drive investment decision-making and include a requirement for SHAs to develop a risk-based asset management plan to improve or preserve the condition of asset condition and system performance (FHWA 2016). The 2017 FHWAâs final rulemaking of national pavement performance measures defines cracking as âan unintentional break in the continuous surface of a pavementâ. In the same final rulemaking, performance measures for different types of pavements are as defined for HPMS reporting. Table 10 provides a summary of the MAP-21 cracking thresholds.
Standard Definitions for Common Types of Pavement Cracking 36 Table 10 Pavement Performance Measures for Cracking (FHWA 2016) Surface Type Metric Measure Range Rating Asphalt Pavement Cracking_Percent <5% 5-20% >20% Good Fair Poor JPCP Cracking_Percent <5% 5-15% >15% Good Fair Poor CRCP Cracking_Percent <5% 5-10% >10% Good Fair Poor Summary The key findings of the review of the desired cracking data by SHAs include: ï· For pavement management, SHAs typically collect transverse, longitudinal, alligator/fatigue, block, and edge cracking for asphalt and composite pavements; transverse, longitudinal, âDâ cracking, corner breaks, and shattered slabs (and others) for JPCP; and transverse, longitudinal, âDâ cracking, and shattered slabs (and others) for CRCP. ï· For HPMS reporting, the desired cracking data includes percent of total wheel path area exhibiting visible fatigue type cracking at all severity levels for asphalt pavements, percent of slabs with transverse cracking for JPCP, and percent area exhibiting longitudinal cracking and punchouts for CRCP. ï· For MEPDG, the desired cracking data includes alligator and transverse cracking for asphalt pavements, percent transverse slab cracking for JPCP, and the number of punchouts for CRCP. ï· Cracking percent is required in MAP-21 (FAST Act).