Agenda - Council - 02/11/2020 - Laserfiche WebLink

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stripping behavior observed in conventional overlays of asphalt (Kandhal & Rickards, 2001). Thus, appropriate drainage is important in chip -sealed pavements. The utilization of subsurface drainage will reduce the probability of saturated subbase and base layers, which will reduce the amount of moisture that would be moving through the pavement. Another factor is to minimize trapped water vapor between the chip seal and the underlying asphalt. If the first lift of pavement is damaged due to insufficient structural capacity to withstand heavy loads (which often occur immediately after the initial lift of bituminous is placed during the construction of a housing development), the pavement may already have significant microscopic sized cracking that allows water vapor to be transmitted from the subgrade soils into the pavement layer and be trapped. Causes of this cracking can include staggered construction of bituminous pavement layers across multiple construction seasons, which subjects the pavement to heavy loads while it is not at full strength. Many of the cities surveyed during this project have explored the use of thin bituminous overlays, approximately five -eighths inches in thickness, as an alternative to chip seal treatments. In Texas, these fine -mix overlays have shown promise as a surface treatment on oxidized pavement and as a surface treatment to extend the life of roadways exhibiting signs of stripping. Studies have shown these thin overlays can extend the service life by an additional three to five years before a mill -and -overlay is required (Newcomb et al., 2013). MnDOT has taken steps toward providing guidance on alternatives to chip -seal treatments. Modifications to Sections 2360 and 3139 of the 2016 MnDOT Standard Specifications for Construction account for the use of an overlay, or "thinlay," using aggregate passing the three -eighths inch sieve as a surface treatment (MnDOT, 2016). As noted, the state of Texas has similar experience and the Texas Department of Transportation has also developed a specification for its fine -mix overlay, detailed in Newcomb et al. (2013). Either of these resources serve as a starting point for municipal efforts in Minnesota. Finally, one observation of this study was a need for better municipal records on both the paving contractor and the paving materials. While many city and county engineers were able to provide valuable detail on their chip -sealed roads for this study, the results and conclusions were limited by a lack of information (as noted in Section 3.4). More detailed records of the contractor and materials would benefit both future research efforts and municipal efforts to maintain roads. 38