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21 Introduction The field composite pavement sections used in the structural modeling primarily included regularly constructed projects from the past 50 years but also a few special research sections. 1. Regularly constructed projects by states, local governments, and other countries: a. Arizona has built many new composite sections consist- ing of a thin ARFC layer over JPC. Two sections of ARFC over CRC also were included. Several heavily trafficked sections in the Phoenix and Tucson areas were included in the database, including one section on I-10 under very heavy traffic for 16 years that shows only a little surficial deterioration. One Arizona HMA/RCC section from the Long-Term Pavement Performance (LTPP) program also was included. b. Ontario has built several sections of HMA/JPC compos- ite pavements, and several were included in the database. c. Washington state has built a few HMA/JPC composite pavements, including one built in 1966 that has gone through three cycles of HMA surface rehabilitation. However, no repair to the JPC has been needed. This pavement section was included in the database. d. Texas has constructed new HMA/CRC composite pave- ments and one of theseâa remarkable 25 years old without any HMA overlaysâwas included. e. Oregon added a thin HMA overlay to an older CRC in excellent condition under very heavy traffic, and this section was included even though it does not meet the ânewâ definition. The existing pavement was not visibly damaged at time of the surfacing with HMA. f. Columbus, Ohio, has built many HMA/RCC composite pavements over the years. Several of these were included in the database as examples of lower truck volume pavements. g. The Illinois Tollway constructed several widening sections with new HMA/JPC in the Chicago area under very heavy traffic. They also constructed two sections (one on an on-ramp and one on an off-ramp) designed and planned by the SHRP 2 R21 research team on I-94 north of Chicago. h. The Netherlands has built more than a dozen porous HMA/CRC composite projects on major freeways since 1998. These projects include 2 to 4 in. of porous HMA over about 10 in. of CRC over an HMA base and other layers for a design life of 40 years (for the CRC). The main motivations are very low noise, no splash/spray, no reflection cracking, and very smooth pavements with surface that lasts more than a dozen years and has no noticeable structural damage. The oldest section was surveyed and included in the database. i. Germany constructed a section of composite SMA/JPC on a very heavily trucked freeway south of Munich that was surveyed and included in the database. This section is more than 13 years old and has carried 47 million trucks with only minor surface deterioration. j. Illinois and Virginia have constructed some new HMA/ CRC composite pavement as widening sections in recent years. These were included in the database. No reflection cracking has developed over time. k. LTPP General Pavement Studies (GPS)-2 sections include a few with HMA over lean concrete, concrete- treated base (CTB), or RCC that could be labeled as composite pavements, and these were included in the database. l. The United Kingdom has built several major highways with a thin surface course system (TSCS) over CRC that have produced excellent performance and low noise. 2. Specially constructed research sections: a. MnROAD included two HMA/JPC composite sections on I-94 under heavy truck traffic and severe weather conditions: ⢠Cell 70 was constructed in May 2010 under SHRP 2 R21. This section was 3-in. HMA over 6-in. JPC C h a p t e r 2 HMA/PCC Test Sections
