Abstract Snow and ice pose danger to users on roadway networks, airports, and parking facilities, requiring large amounts of deicing or anti-icing chemicals. The environmental impacts of deicing/anti-icing chemicals, typically chloride-based salts, can include degraded drinking water supplies and destruction of native aquatic and terrestrial flora and fauna, which can promote the spread of invasive species. This study investigates an alternative to chloride-based salts, which involves the application of a sand type that has been rarely used in North America, namely water-heated sand. In this study, we measured the friction coefficient on asphalt pavement core samples below freezing temperature for several winter road surface treatment conditions, including bare pavement, bare ice, dry sand on ice, and water-heated sand on ice. As expected, bare pavement produced the highest friction, while bare ice produced the lowest friction. Dry sand on bare ice exhibited friction similar to that of untreated bare ice. Water-heated sand melts into ice on the road surface and refreezes, while still protruding above the ice. The increased surface roughness of water-heated sand is an effective alternative to chemical treatments for improving winter road safety, while also reducing negative environmental impacts.
Abstract Lead [Pb(II)] contamination poses a significant environmental concern due to its detrimental effects on soil physicochemical (i.e., physical and chemical) properties and structural stability. This issue is further exacerbated by freeze–thaw (F-T) cycles, which accelerate the migration and redistribution of heavy metals. Traditional solidification/stabilization (S/S) technology has been widely employed for soil remediation, with cement-based stabilization being the most commonly adopted approach. However, ordinary portland cement, the primary binder used in conventional S/S systems, is associated with significant environmental drawbacks, including high carbon emissions and energy consumption. As a sustainable alternative, geopolymer stabilization has attracted increasing attention due to its lower environmental impact and strong capacity for immobilizing heavy metals. In this study, slag and fly ash were utilized as aluminosilicate precursors, while solid sodium hydroxide (NaOH) and sodium silicate (Na 2 SiO 3 ) served as alkaline activators to synthesize NaOH-activated geopolymer (SHG) and Na 2 SiO 3 -activated geopolymer (SSG) via a one-part geopolymer system. The stabilized Pb(II)-contaminated soil was subjected to F-T cycles, and their macroscopic characteristics and mechanical properties, including mass loss, unconfined compressive strength (UCS), UCS loss, and pH value, were systematically evaluated. Pb(II) leaching concentration was determined using inductively coupled plasma mass spectrometry. Furthermore, the F-T resistance mechanism was investigated via microstructure analysis, and structure degradation was quantified using Image-Pro Plus (IPP, version 6.0) to evaluate soil looseness. An F-T damage prediction model was also established to characterize the evolution of mechanical deterioration. The results revealed that mass loss increased with increasing Pb(II) concentration and F-T cycles but remained below 5%. UCS loss exhibited a similar trend, with the most significant reduction occurring after the first F-T cycle. Although SSG exhibited higher initial UCS, it showed greater susceptibility to F-T damage compared with SHG. Performance degradation was primarily attributed to pore expansion and crack propagation, resulting in increased structural looseness. Despite a slight increase in Pb(II) leaching after F-T cycles, the stabilization efficiency remained above 99%. The proposed prediction model provides valuable insights for optimizing one-part geopolymer systems for stabilizing heavy metal–contaminated soil in seasonally frozen regions.
Abstract Because of the complex temperature conditions in cold regions, the slab track is prone to defects such as interlayer debonding, voiding, and other diseases, significantly affecting high-speed railway operations. An efficient method of providing thermal insulation on a slab track is to apply insulating materials to the concrete's surface. In this study, the distribution characteristics of the temperature field of the slab track under various thermal insulation measures were comparatively analyzed by using long-term monitoring full-scale experiments, and the thermal insulation effect of the selected measures in different seasons was quantified. The findings include: (1) Insulation measures reduce heat transfer between the environment and the track, enhancing thermal insulation. (2) As the measured extreme value of the negative temperature gradient of the track slab −46.91°C/m exceeds the specified minimum design value (−45°C/m), it is recommended to customize the design values of negative temperature gradients based on local conditions in various cold regions. (3) The thermal insulation measure reduces the maximum temperature gradient of track slabs by 44°C/m in summer and 18°C/m in winter compared with no insulation, impacting the duration of positive and negative temperature gradient effects. (4) The temperature field distribution on both sides of the track structure differs due to varying solar radiation.
