Evaluation of a permissible roadbed thawing depth in permafrost

Roadbed thermal conditions in permafrost are subject to seasonal changes affecting roadway resilience. A roadbed thawing depth is important for road base processing, especially in permafrost. This research had the purpose of evaluation of a permissible roadbed thawing depth based on the Biot number reflecting general thermal resistance of roadbed layers. These results will contribute to understanding road bed thermal resistance and selection of roadway construction materials.

Life Cycle Economic and Environmental Impacts of CDW Recycled Aggregates in Roadway Construction and Rehabilitation

The use of recycled materials in roadway construction and rehabilitation can achieve significant benefits in saving natural resources, reducing energy, greenhouse gas emissions and costs. Construction and demolition waste (CDW) recycled aggregate as an alternative to natural one can enhance sustainability benefits in roadway infrastructure. The objective of this study was to quantitatively assess the life cycle economic and environmental benefits when alternative stabilized-CDW aggregates are used in pavement construction. Comparative analysis was conducted on a pavement project representative of typical construction practices in northern Italy so as to quantify such benefits. The proposed alternative sustainable construction strategies considered CDW aggregates stabilized with both cement and cement kiln dust (CKD) for the base layer of the roadway. The life cycle assessment results indicate that using CDW aggregate stabilized with CKD results in considerable cost savings and environmental benefits due to (i) lower energy consumption and emissions generation during material processing and (ii) reduction in landfill disposal. The benefits illustrated in this analysis should encourage the wider adoption of stabilized CDW aggregate in roadway construction and rehabilitation. In terms of transferability, the analysis approach suggested in this study can be used to assess the economic and environmental benefits of these and other recycled materials in roadway infrastructure elsewhere.

Effect of Nanoclay Particles on the Performance of High-Density Polyethylene-Modified Asphalt Concrete Mixture

Utilizing polymers for asphalt concrete (AC) mixture modification has many drawbacks that hinder its wide implementations for roadway construction. Recently, research on employing complementary materials, such as nanomaterials, to balance negative impacts of polymers while enhancing the AC mixture’s performance has received great attention. This study aimed to investigate the effect of incorporating nanoclay (NC) particles on the performance of a high-density polyethylene (HDPE)-modified AC mixture. A 60/70 asphalt binder was first modified with HDPE, and then NC particles were gradually added at a concentration of 1–4% by weight of the asphalt binder. The binders’ physical characteristics, storage stability, and chemical change were scrutinized. AC mixture performance, including pseudo-stiffness, moisture damage resistance, stripping susceptibility, and rutting tendency, was investigated. A statistical analysis on the experimental results was conducted using Kruskal–Wallis and Dunn tests. Test results showed that employing NC/HDPE significantly increased penetration index and thereby enhanced binder temperature sensitivity. Moreover, it prevented oxidation action and separation and, therefore, enhanced binder storage stability. Furthermore, incorporating NC amplified pseudo-stiffness and significantly improved resistance against moisture damage and stripping of HDPE-modified mixtures. Moreover, it improved both elastic (recoverable) and plastic (unrecoverable) deformations of mixtures. The most satisfactory results were attained when incorporating 3% of NC.

Technology of eliminating outburst by downward drilling in highground pressure and serious outburst area

The high-drainage roadway construction face of the working face is used to pre-drill the borehole under the tunneling face, and the problem of poor water return in the hole is solved by grouting the surrounding rock cracks in the deep and shallow holes of the drill floor. The “two plugs and one note” sealing method was adopted to ensure that the sealing holes were tight and airtight; the water pipes were blown all the way in the hole, and the single hole, grouping and timed water blowing work targets were realized, and the drilling effect of the downhole drilling was improved. A set of efficient and rapid down-drilling and hole-dissipation management mode has been formed, which has achieved the goal of high-efficiency outburst of coal seams and technical and economic integration in areas with high ground pressure and serious safety and economic benefits.

Effects of Market Concentration and Competition in the Paving Sector

Planning agencies are searching for innovative techniques to cost effectively preserve their existing infrastructure systems. In this study, we investigate the effects of two indicators of increased competition in the paving market as a mechanism to reduce roadway construction costs. The highway construction sector makes for a unique case study due to a rich dataset that allows for the simultaneous consideration of two indicators of competitive intensity: number of bidders on a project (an indicator of intra-industry competition – between firms who pave with the same material) and market concentration (an indicator of inter-industry competition – between firms who pave with material substitutes). To evaluate the relationship among these indicators and pricing, we develop panel data regression models using bid data that spans 10 years for 47 states within the United States. The models embed several covariates that account for cross-sectional and time-varying heterogeneity. Results from the analyses indicate both that a) the paving market functions as a private value auction, in which an increase in bidders reduces construction prices and b) states with more uniform market shares among pavement materials pay lower prices for all materials. For a “typical” roadway project, the parameterized model indicates that states that with the lowest quartile of market concentration pay at least 7% less than states with the highest quartile of market concentration. These findings support the notion that policies that reduce material market concentration have the potential to reduce an agency’s costs, allowing it to be more efficient with its limited resources.

A comparison of the carbon footprint of pavement infrastructure and associated materials in Indiana and Oklahoma

<p><span>Although often overlooked, infrastructure has a significant role in modern society. It is necessary means of transportation for goods and services needed to support commerce. It is this need and the need for continued economic development that causes the continuous infrastructure construction and its’ associated greenhouse gas emissions. Infrastructure construction requires energy to process raw materials, transport, mix and final construction. Greenhouse gas emissions from pavement sections have previously been identified for pavement preservation techniques. This research further evaluates greenhouse gas emissions for typical pavement sections from Indiana and Oklahoma to determine the carbon footprint based on linear foot of pavement. The comparison of CO2e of two typical roadway sections finds the difference in carbon footprint since variation in their minimum roadway. The carbon footprint of typical utility pipe with HDPE produces minimum CO2e and steel produces maximum CO2e. Soil base remediation options produce minimum CO2e and stabilized aggregate base produces maximum CO2e. Carbon offsets are determined by choosing vegetative options, soil remediation methods and appropriate pavement. This study is limited to a few pavement sections with a small variety of typical anticipated carbon offsets that would be seen in roadway construction. The index presented allows users to simply quantify benefits of the carbon offsets.</span></p>

A multi-model approach toward understanding iron fouling at rock-fill drainage sites along roadways in New Hampshire, USA

Factors affecting iron fouling in wet areas adjacent to roadways were investigated by collecting field rock cut and aqueous physicochemical data; developing exploratory predictive models; and developing geochemical models. Basic data included the identification of iron fouling from aerial imagery and field visits at 374 New Hampshire rock cut locations, and their associated rock-fill sites. Based on field water quality measurements from wet areas at 36 of the rock-fill sites, the occurrence of iron fouling was associated with higher values of specific conductance, lower concentrations of dissolved oxygen and lower pH compared to areas without iron fouling. A statistical model, using boosted regression trees, was developed to predict the occurrence of iron fouling in wet areas adjacent to roadways where rock-fill from nearby rock cuts was used in roadway construction. The model was used to develop a continuous iron fouling probability map for the state of New Hampshire that can be used to better understand the occurrence of iron fouling. Geochemical models illustrate how iron fouling of waters increases along roadways built with fill from sulfidic rock cuts as a result of acid generation from pyrite dissolution and ferrous iron (Fe2+) oxidation and increases in areas with greater specific conductance from deicing runoff caused by cation exchange. More iron is precipitated as goethite in simulations that include pyrite, and in simulations with deicing salts added, indicating that rock-fill sites with rocks that contain pyrite and water with greater salt content could have enhanced iron fouling.