Since paving was completed in October 1990 nine years of very good service have occurred, far more than expected. Each year data for each mile was recorded by the ADOT Pavement Management Section (PMS). In addition this section also retrieves the traffic loading data and the pavement surface maintenance data from other computer files. Table 2 shows the average yearly summary of pavement performance data for the 33.3km (20 miles) of pavement. In addition the data is also shown representative of the pavement condition before overlay. As can be seen virtually no reflective cracking has occurred since construction. The ride is expressed in inches per mile units and is indicative of a very smooth riding surface. The rut depth is virtually not existent. Skid resistance as measured by the Mu meter is good. Maintenance costs have been low throughout the life of the overlay.

For comparative purposes the adjoining section of Interstate 40 referred to as the Riordan project (milepost marker 191 to 195) was reconstructed in 1985 and 1986 under two separate construction projects. The old very badly cracked concrete pavement was removed and crushed for aggregate base. The existing cement treated base had turned to a mushy poor quality material and was wasted. The wet clay subgrade was regraded and an edge drain system constructed. A geotextile separation layer was placed followed by 100-175mm (four to seven inches) of aggregate base. The aggregate base was then covered with 150mm (six inches) of a asphalt permeable base. The final HMA was 200-275mm (eight to eleven inches) in thickness (Figure 3). All of the HMA was built with an AC-20 binder. The two construction projects required detours and two years of construction. The total cost for about four miles of new pavement was $14 million. For comparative purposes Table 3 shows the distress history of these two Riordan reconstruction projects as measured by the ADOT PMS. Cracking of the 200-275mm (eight to eleven inch) pavements began in the second year and proceeded to a degree requiring

rehabilitation by the tenth year. Other pavement performance measures indicated that the pavement was performing very poorly.

Another comparison of how well the ADOT AR section have performed can be seen from reviewing Strategic Highway Research Project test sections built as part of the Flagstaff overlay project. The Flagstaff project was selected as an SPS-6 concrete rehabilitation test project. Table 4 shows the layout of the test sections. ADOT decided to build several of its own test section to be included in the study. The test section are all located in the east bound direction of Interstate 40 from mile post marker 202.16 to 204.26. SHRP test section 040608 is a 200mm (eight inch) overlay of the concrete pavement. Test section 040607, 040606 and 040659 are all 100mm (four inch) overlays of the concrete pavement. The 200mm & 100mm (eight and four inch) overlay test sections were all built using the ADOT HMA base mix with 4.6% asphalt with AC-20 binder. Test section 040661 was an ADOT test section composed of a two inch overlay of ADOT HMA base mix followed by a 50mm (two inch) overlay with the AR gap graded mix with 6.5% binder. Table 4 shows the cracking by year in lineal feet of cracking (5). These crack measurements were estimated from the LTPP file and from the crack maps and/or ADOT photos and field reviews. Again this table shows how well the AR sections are performing compared to the other conventional overlays. Figure 4 shows a photo taken from 19.8m (65 feet) above the test section by using an ADOT cherry picker (high boom) truck. It clearly shows the degree of cracking in the 100mm (four inch) overlay and the lack of cracking in the AR test section.