Journal of Cold Regions Engineering

Diatomite is a highly porous media with significant water absorption and retention capacity. In order to investigate the long-term cooling effect of diatomite on a roadbed in a warm permafrost region, a diatomite embankment was constructed in 2003, on National Highway 214, Qinghai-Tibet Plateau. Field data revealed that surface temperature differences between embankments with and without diatomite varied from 0.3 to 1.8°C. According to permafrost tables and mean annual ground temperatures, the thermal semiconductivity of a 0.4-m thick diatomite slope only impeded permafrost degradation, but did not offset the temperature rise associated with installing an asphalt pavement and embankment in warm permafrost regions. Further analysis indicated that the initial cooling effect of the diatomite slope was influenced by the construction season and watering treatment. Additionally, maintenance and climatic conditions were important for the long-term thermal performance of the diatomite embankment. The results show that diatomite slopes should be considered in humid climates with high levels of autumn rainfall, and should ideally be constructed at the end of winter.

The study examined the individual and combined effects of potassium ferrate(VI) and freeze-thaw treatment for the inactivation of Escherichia coli (E. coli) in a phosphate buffered saline (PBS) solution. A low dose (LD) of $0.5\mathrm{mg}/\mathrm{L}$ and a high dose (HD) of $1.0\mathrm{mg}/\mathrm{L}$ of potassium ferrate(VI) were used as a pretreatment and posttreatment to freeze-thaw, at temperatures of $-10$, $-20$, and $-30°\mathrm{C}$, for 1, 8, and 15 days completely frozen. The LD did not have a significant effect on E. coli concentrations following a 15-min contact time. However, when the LD was used as a pretreatment to freeze-thaw, E. coli concentrations were reduced to $<0.18\mathrm{MPN}/\mathrm{mL}$, representing by $>6\text{-}\log$ inactivation, regardless of the freezing temperature or the duration of the freezing conditions. When used as a posttreatment to freeze-thaw, LD improved E. coli inactivation compared to stand-alone freeze-thaw treatments; however, LD was much more effective when used as a pretreatment to freeze-thaw. The HD resulted in up to 6.4-log inactivation of E. coli following a 15-min contact time. When used as a pretreatment to freeze-thaw, E. coli concentrations were reduced by more than 6-log regardless of the freezing temperature or the duration of the freezing conditions, similar to the pretreatment tests with LD. Stand-alone freeze-thaw treatments at temperatures of $-10$, $-20$, and $-30°\mathrm{C}$, for 1, 8, and 15 days resulted in 1.4 to 3-log inactivation of E. coli, with no significant difference among the various freezing temperatures and freezing times. The study confirmed the effectiveness of potassium ferrate(VI) and freeze-thaw treatments for the inactivation of E. coli and also demonstrated that relatively low doses of potassium ferrate(VI) are extremely effective when used as a pretreatment, prior to freeze-thaw.

Snow removal and ice control are critical to the safe and efficient use of roadways in much of the world. Tools that help road authorities plan for, assess, and communicate about winter maintenance activities are increasingly being sought. Weather indices that rate the severity of winter conditions in a given period at a particular location are one subset of such tools. Although several winter severity indices have been developed, many of these are complex and of limited practical use for road authorities. In this research, an approach for developing a simple-to-use, locally calibrated winter severity index (WSI) is outlined. The approach relies primarily on mathematical optimization but is flexible enough to allow expert knowledge to be incorporated. This approach is used in developing a WSI for the provincial highway system of the province of Alberta, Canada. The WSI assigns each day a weather score based on seven weather attributes and one seasonal adjustment factor. By using a classification and regression approach, the eight components are based on attribute-specific thresholds that then trigger a score. These daily scores are aggregated to the 14-day period and are correlated to maintenance activities. The WSI for Alberta highways has strong fit with maintenance activity that occurred, when measured as vehicle hours. At the 14-day level, the $R^2$ values for vehicle hours vary from 0.776 to 0.936 for eight contract areas, and when the data are aggregated over space or time, the fit improves further. This research illustrates how site-specific WSIs can be developed for road authorities through the use of optimization that alters the weather attribute thresholds and scores, reflecting the specific maintenance regimes in that location.

This paper presents insights from two small flumes used to compare ice conveyance and jam initiation between straight and sinuous channels of rectangular cross section, and to investigate ice accumulation and jam morphology in sinuous channels. The findings indicate conditions, expressed in terms of Froude number and ice-piece size relative to channel width, limiting ice conveyance and leading to jam initiation in sinuous and straight channels. The sinuous channel is found to have a larger capacity to convey ice floes than the straight channel of the same flow cross section. Velocity nonuniformity, including higher velocities near the outer bank of bends, contributes to this insight. Jams formed by relatively small floes have a nonuniform thickness through the sinuous channel and are thickest along the inner banks. The thickness variation reduces as floe size increases. Accumulation and jam morphology are analogous to alluvial sediment morphology in sinuous channels. The paper also presents suggestions for aspects in need of further laboratory and numerical investigation and further field observations.

This paper presents an overview of the effects of environmental factors, namely moisture and temperature, on the material properties of flexible pavement road structure considered in the design guides of AASHTO. It considers the historical development of AASHTO design guides with new design guides. The study showed the shift in emphasis from total reliance on an empirical method to a combination of mechanistic and empirical methods in the new design guide. Further, moisture and temperature were indirectly considered in the current guide, whereas these parameters are accounted for in the new design guide through the resilient modulus and the complex modulus. The sensitivity analyses of environmental consideration using the new design guide software are presented in this paper.

This paper is a continuation of an earlier overview on the subject and presents the results of a sensitivity analysis that assessed the ability of the new design guide to portray the impact of temperature and moisture content on flexible pavement performance. The study used the most common asphalt concrete (HL3) and unbound materials (granular A and silty sand) used in Canada. Two binders [performance grade (PG) 52-34 and PG 58-28] and three moisture conditions (dry, wet, and optimum) were chosen. Designs performed using Level 3 analysis for unbound materials and Level 1 for asphalt concrete showed that the new design guide is sensitive to binder performance grades and climatic zones (cold versus warm); however, the new design guide showed limited sensitivity to the state of unbound materials: permanent deformation showed negligible changes between wet, dry, and optimum conditions. Model simulations indicated that rutting that accumulated throughout the 20-year design life for the warm region (Long Beach, California) was 50% more than that in the relatively cold region (New York). Using different soil conditions for unbound materials showed that the increase in resilient modulus from wet to dry conditions increases total rutting by 27%. Results also demonstrated good sensitivity to the type of asphalt binder and agreed with the binder type objective: the HL3 mix prepared with the PG 58-28 binder substantially decreased rutting (by 271%) compared with the mix prepared with the PG 52-34 binder.

Mathematical modeling (simulation) of the movement of the air mixture in the combustion of natural gas was performed for coaxial flue tubes with countercurrent flow for conditions of extremely low ambient temperatures. Also investigated was a configuration of the flue tube in which the chimney was modified with a 45° corner cut, characterized by less icing. The calculation and analysis of 24 cases were carried out.

Previous studies have focused on the optimal hydraulic section for ice-free channels only. This paper presents the optimal trapezoidal section and its characteristics under ice-covered conditions. Using the Lagrange multiplier optimization method, formulas for the dimensions of the optimal hydraulic trapezoidal section are derived. The results show that the optimal hydraulic section under ice-covered conditions is different from that under ice-free conditions. The optimal width-to-depth ratio depends not only on the side slope, but also on the roughness coefficients of the ice cover and channel bed (bottom and sides). The ratio of bed roughness (or ice-cover roughness) to composite roughness is another key parameter in determining the shape of the optimal section. The comparison with the ice-free section shows that the optimal hydraulic section under ice-covered conditions is relatively narrow and deep, which helps reduce the heat loss at the water surface. Practical aspects of the optimal hydraulic section under ice-covered conditions are addressed.

Four commercially available snow- and ice-control products made from naturally sourced materials were tested laboratory. Using 23 wt. % NaCl (salt brine) as a control, ice-melting performance, corrosion impacts to carbon steel, and impacts to portland cement concrete were determined.. All four liquid deicer products showed significantly lower corrosion rates than the salt brine control, whereas their ice-melting capacity at $-9.4°\mathrm{C}$ (15°F) and $-15°\mathrm{C}$ (5°F) varied. Coupled with 10 freeze–thaw cycles, the naturally sourced liquid deicers induced less mass loss but more reduction in splitting tensile strength of non–air-entrained concrete specimens relative to the salt brine. The porosity of each concrete sample was calculated from X-ray microcomputed tomography images to determine the effects of the deicer and freeze–thaw exposure on the concrete. Relative to water, two liquid deicers induced more significant porosity of the concrete, whereas the salt brine and one liquid deicer increased its porosity. The analytical hierarchy process was demonstrated for the integration of test results, assisting winter maintenance agencies in the proper selection of a product depending on specific user priorities. All of the naturally sourced deicers featured higher scores than the salt brine control under the investigated conditions and given priorities.