Journal of Cold Regions Engineering

Polymer-modified asphalts are used in Alaska to address problems with rutting, cracking, and premature aging. This usage raises two important issues—the improvement of the pavement performance with polymer modification while maintaining the ability to properly place and compact polymer-modified mixes. This study addresses both issues. Base asphalts and polymer-modified binders were analyzed for storage stability, compatibility, and consistency using traditional and Superpave tests. Thermal stress restrained specimen tests and Georgia wheel rutting tests were conducted for asphalt-aggregate mixtures. The test results indicate that polymer-modified asphalts should always be an end result of an extensive product development program. The premanufactured binders had the best performance and workability. The polymer modification improved the performance of all base asphalts in several polymer-asphalt combinations. Some binders smoked excessively during mixing, which warrants further research. A storage stability test should be added to specifications or the contractor should address the storage stability with techniques such as tank circulation. On the basis of the test results, the Superpave PG grading needs to be adjusted for polymer-modified asphalts.

The extent to which alluvial channels respond to ice-cover formation, presence, and breakup is not well understood. Some responses are well known and observed, such as increased flow stage or localized scour beneath the toe of an ice jam. Other responses are known in concept, such as altered bedform geometry, but are not well documented. Some potential responses are barely recognized, such as channel-thalweg adjustment. Many responses are temporal, such as the channel readjusting itself once ice is gone. A few responses may have a more enduring impact, such as a meander-loop cutoff. Most responses have not been investigated rigorously. The responses affect the full gamut of relationships between flow discharge and stage, macroturbulence structures, sediment-transport and mixing processes, and alluvial-channel stability. Of importance are the relative scales of length and time associated with ice-cover formation, presence and breakup, and a channel’s facility to respond to ice. This paper reviews alluvial-channel responses to ice formation, and raises practical engineering issues stemming from them.

Interior Alaska has indoor air quality issues similar to those of other far northern communities associated with long cold winters and reduced ventilation rates. Moreover, geological features in the hills around Fairbanks, Alaska increase the likelihood of elevated radon levels. To better quantify these features, our team has gathered data at 68 homes. We used ${\mathrm{CO}}_2$ concentrations as a surrogate for indoor air quality as well as to help determine ventilation rates to be used in subsequent modeling work. We found the ${\mathrm{CO}}_2$ data correlated well using basic mass conservation considerations for yearly averages. The summer CO values ranged from 1 to 9 ppm and the winter values from 0 to 23 ppm. For homes with woodstoves, we found the indoor ${\mathrm{PM}}_{10}$ concentrations rose after the stoves were fired up. Here ${\mathrm{PM}}_{10}$ refers to particles smaller than 10 μm. Over 40% of the tested homes in the hills around Fairbanks had radon $\mathrm{levels}>4\mathrm{pCi}/L$ compared to a nationwide average of 7%. Active subslab depressurization systems tested were very effective in reducing indoor radon concentrations (average reduction of over 90% for eight homes).