James Bryce

A life cycle assessment of in-place recycling and conventional pavement construction and maintenance practices

The application of in-place recycling techniques has emerged as a practical and effective way to enhance the sustainability of agency pavement management decisions for asphalt-surfaced pavements. However, the potential environmental benefits resulting from applying in-place recycling techniques have not been fully documented in the literature. This paper presents a comprehensive pavement life cycle assessment (LCA) model that extends the typical pavement LCAs system boundaries to include the environmental impacts resulting from the usage phase and the production of the energy sources. The results of the application of the pavement LCA model to a specific highway rehabilitation project in the state of Virginia showed that in-place recycling practices and an effective control of the pavement roughness can improve significantly the life cycle environmental performance of a pavement system.

Wavelet Denoising of TSD Deflection Slope Measurements for Improved Pavement Structural Evaluation

Nondestructive testing devices are widely used to assess the structural condition and bearing capacity of pavement systems. Continuous deflection devices (CDDs) can safely measure pavement deflection (or other related properties) while traveling at highway speed, which reduces traffic disruption. However, CDD measurements are contaminated with relatively high noise levels compared to stop-and-go devices such as the Falling Weight Deflectometer (FWD). The objective of this article is to evaluate the structural condition of pavement sections using Traffic Speed Deflectometer (TSD) deflection slope measurements. The authors use wavelet transform denoising to: (1) identify localized weak spots such as those that are caused by pavement reflection cracking; and (2) denoise deflection slope measurements to calculate the effective structural number of the pavement. Results show that failure to denoise deflection slope measurements can lead to calculated values that are highly variable (unstable). Attempting to filter these highly variable measurements can lead to erroneous results.

Assessment of Continuous Pavement Deflection Measuring Technologies

This report documents the results of a study that evaluated current technologies implemented in continuous deflection measuring devices. The research team assessed the demand and the potential value of continuous deflection devices for supporting pavement renewal decisions, and identified the technologies best suited for effectively supporting the most critical decisions identified by the potential users through a survey of state departments of transportation. The study produced a catalogue of existing continuous deflection measuring technologies and their characteristics. The capabilities of two devices, that are or showed the most promise to be ready for production use, were reviewed and practical applications for supporting pavement management decision-making identified and illustrated. The Rolling Wheel Deflectometer (RWD) and Traffic Speed Deflectometer (TSD) were selected for further study as these were identified as being in or close to production mode and met the criteria of measurement speed, applied loads and data collection frequency. However, detailed evaluation was only possible for the TSD because the RWD was not available for testing. The research confirmed that, in general, the technology can provide adequate repeatability for network-level data collection and can be used to support critical network-level pavement management business processes. However, the study also showed that the technology is only just maturing and identified possible improvement to make it even more useful and practical.

Developing a Network-Level Structural Capacity Index for Asphalt Pavements

This paper presents a network-level structural capacity indicator for asphalt pavements in the state of Virginia. A literature review revealed that several network-level structural capacity indexes have been proposed, and a number of states use structural capacity measures in their network-level decision processes. Some decision methods and structural indexes are compared in this paper using network-level deflection data collected using the falling weight deflectometer and distress data from tests conducted on Virginia interstates. One index that is based on the structural number concept, the Structural Capacity Index, is found to produce network-level decisions that most closely match project-level work done by the Virginia Department of Transportation during the 2008 construction season. The index was adopted, and its sensitivity to various input parameters was determined. Furthermore, the impact of the structural capacity of the pavement on the service life of a pavement maintenance treatment was clearly established in this paper. Equations to define the service life of a corrective maintenance treatment as a function of the structural condition of the pavement are also presented in this paper.

Limits of agreement method for comparing TSD and FWD measurements

This article uses the limits of agreement (LOA) method to compare the falling weight deflectometer (FWD) and the traffic speed deflectometer (TSD), two pavement structural evaluation devices. The TSD measures deflection slope, whereas the FWD measures deflection. For this reason, measurements were converted to the surface curvature index (SCI) and the base damage index (BDI), which can be obtained from each device. The SCI and BDI agreement between the two devices was then evaluated. Although the relationship between the calculated SCI and BDI using both equipments is reasonably close to the line of equality, there is a significant variation and a bias in this relationship. For example, for an average SCI or BDI value of 300 μm, the bias was 30 μm (FWD values lower than TSD values), and the LOA was 380 μm.

Evaluation of Traffic-Speed Deflectometers

Continuous deflection-measuring devices, or continuous deflectometers, are increasingly being used to support project-level and network-level pavement management decisions. Continuous deflectometers are nondestructive pavement evaluation devices that measure pavement deflections caused by a moving load. Some continuous deflectometers can measure with little to no traffic control; this feature makes them more advantageous to use than stationary devices, such as the falling weight deflectometer. The current technologies implemented in different types of deflectometers are discussed, and the most promising devices for supporting network-level pavement management decisions are identified. In that respect, two devices (the rolling wheel deflectometer and the traffic speed deflectometer) have shown promising results and are being evaluated further under Project R06 (F) of SHRP 2.

A comprehensive life cycle costs analysis of in-place recycling and conventional pavement construction and maintenance practices

Abstract Recent studies based on Life Cycle Assessment (LCA) have highlighted the potential of in-place recycling techniques to enhance the sustainability of agency pavement management decisions for asphalt pavements. However, a solution which an LCA finds environmentally advantageous might not be preferred over another which is technically equivalent, if it is not economically competitive. In this context, it is necessary to evaluate the economic costs of such alternatives taking into account the perspective of the main stakeholders who interact with a pavement system throughout its life cycle. This paper presents a comprehensive pavement life cycle costs (LCC) model that accounts for the different categories of costs incurred by highway agencies and road users in every phase of the pavement life cycle. The results of the application of the pavement LCC model to a specific highway rehabilitation project in the state of Virginia showed that in-place recycling practices are beneficial for both highway agencies and road users.

Enhancing Network-Level Decision Making Through the Use of a Structural Capacity Index

The objective of this study was to show potential applications of a network-level structural index developed for evaluation of flexible pavements. First, several potential applications for implementation of network-level structural measures were identified, and then data from the state of Virginia were used to modify the proposed applications for the index and show examples of them. Several applications were validated with data from network-level deflection testing with the falling weight deflectometer on Interstate highways in Virginia and data from the Virginia Department of Transportation Pavement Management System. The results of the research indicate that including the structural index in the network-level decision process can facilitate a greater understanding of the behavior of the performance of a pavement. Furthermore, the index that was proposed for network-level evaluation of flexible pavements in Virginia was used to develop enhanced deterioration models for particular pavement treatments and to demonstrate the dependence of pavement performance on its structural capacity. It was shown that the functional characteristics of a pavement alone were not adequate to describe the structural condition of the pavement. Therefore, the structural condition, for example, as based on the results of deflection testing, should be considered when network-level pavement management decisions are made.

Probabilistic Life-Cycle Assessment as Network-Level Evaluation Tool for Use and Maintenance Phases of Pavements

Agencies that manage pavement networks have a role in mitigating the factors affecting global climate change by managing their networks in such a way that these factors are minimized. Although much research is still required to quantify the climate change impact of many variables relating to pavements, the impact of pavement condition on vehicle fuel consumption has been clearly demonstrated in several research projects. In the light of extensive research that shows pavement characteristics as having a significant impact on vehicle fuel consumption, it can be shown that maintaining a network of pavements to minimize roughness can limit the energy consumption of vehicles traveling along the pavement network. The objective of this study was to demonstrate a method by which transportation agencies could measure the impact of their management decisions on reducing the energy consumption of their networks. The use of a life-cycle assessment (LCA) to quantify energy consumption probabilistically for a given set of expected maintenance actions defined at the network level is demonstrated. This study shows how the results of the LCA can be used to evaluate the energy consumption attributed to the pavement network over a defined time frame.

Sustainable Pavement Management

Sustainable pavement management as a business practice is about facilitating pavement investment trade-offs considering the triple bottom line of sustainability during the design, construction, maintenance, and rehabilitation of pavements. This chapter discusses the basic principles of pavement management and the changes necessary to help pavement manager make more sustainable decisions. It discusses the various levels of pavement management decisions, the importance of pavement management as a key asset management business process, and the data needed to support the various levels of analysis. A more sustainable decision-making pro-cess requires tools for analyzing the economic, environmental, and social impacts, as well as for comparing the pavement investment trade-offs. The chapter reviews some of these tools, provides guidelines for incorporating sustainability into the various levels pavement management decision making, and recommendations for making pavement management systems sustainable within an organization.