WMA lowers the viscosity of asphalt concrete. By lowering the viscosity, benefits might include better compaction, slower cooling rates, reduced mixture aging, allowance for longer haul distances, and more options for maintenance activities like patching in colder weather. These conditions may result in better capabilities to pave and compact at cooler temperatures, such as those experienced in South Dakota during the early and late construction season, and thus provide more options for paving operations during less than ideal weather conditions.
To assess the relative merits of employing WMA paving techniques in the state, the South Dakota Department of Transportation (SDDOT) would need to construct pavement test sections with WMA. The primary aims of WMA evaluation would be to:
- examine the suitability of using WMA in South Dakota's climate;
- assess WMA pavement and paving operations in overlays, interim surfacing, and/or leveling courses;
- evaluate the mechanistic and chemical properties of WMA binders and mixtures;
- assess the performance of quartzite, limestone, and natural gravels in WMA pavements, which are the 3 primary aggregate types native to South Dakota, and also perform similar assessments relative to various quantities by weight of recycled asphalt pavement (RAP);
- ascertain the structural integrity, durability, and moisture susceptibility of WMA in comparison to conventional HMA pavements;
- gain measures of relative emissions during production and paving with WMA as compared to HMA.
To fully accomplish the desired WMA assessment, the test pavement construction should not be a simple thin overlay or wearing course. A simple thin overlay wouldn`t necessarily give a full representation of structural integrity. Also, paving operations should be scheduled late in the construction season when the weather is cooler to truly determine whether WMA placement is a viable alternative during less than ideal weather conditions. Finally, test sections would need to be monitored for an extended period of time after construction.