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One city that switched from ordinary compaction to maximum density stated that the asphalt pavement <br />was the same price. The contractor used two 20 to 25 ton double drum steel roller and a pneumatic <br />roller when maximum density was specified. Prior to specification using the maximum density <br />contractor on an ordinary compaction job had only one 6 to 8 ton roller on the job. <br />Recommendations <br />1. Switch from 2340 mixture requirements to 2360 level 2 or 3 as need for traffic. <br />2. Use specified density for compaction <br />a. The use of the MnDOT's incentive program is optional. <br />3. Pay close attention to areas that are difficult to pave and compact. <br />a. Sharp radius, skewed intersections, cross streets etc... <br />4. Spend more time and effort on inspection of paving <br />5. If doing a mill and over lay then the existing street should be cored to determine quality of <br />base course before designing project. <br />6. Chip seal earlier in pavement life. <br />Additional Needs for Research <br />1. Bond strength of tack coat bond strength <br />a. In coring many streets as part of this project, the lack of bonding of base course to wear <br />course of HMA is very apparent. <br />b. It is hypothesized that the lack of strong bond reduces the durability of the wear course <br />because it is independent of the underlying layers, causing movement between layers. <br />This movement could increase the stripping effect. <br />2. Study priming granular base materials before paving to waterproof bottom of the asphalt <br />pavements. <br />3. Develop quick setting fog sealing product. <br />a. Lab testing done as part of this study shows that a fog seal will keep water out but still <br />all water vapors to migrate out of the HMA. <br />4. Study using lower air voids design mixes <br />a. Maybe as low as 1 to 2% <br />5. Use softer based asphalt binder <br />a. PG -34 <br />D-4 <br />