Matthew W. Frost

Review of Lightweight Deflectometer for Routine in Situ Assessment of Pavement Material Stiffness

The use of a portable lightweight deflectometer (LWD) for construction quality control or material investigation for earthworks and road construction is increasing around the world. LWD is reviewed as a field evaluation tool, the test variables and data quality are discussed, and the usefulness and limitations for a variety of earthwork and road assessment scenarios are described. A state-of-the-art reference document is provided for LWD users, consultants, material specifiers, contractors, and clients. Data from road foundations (subgrades, granular capping, and subbase) and fully constructed in-service (thinly surfaced) roads were reviewed to demonstrate the flexibility of the LWD and to show that its determination of stiffness modulus may differ from that of the conventional falling weight deflectometer to a varying extent. A series of laboratory investigations was undertaken to demonstrate the sensitivity to uniformity of plate-surface contact and the limitations in the interpretation of peak displacement from the device. A good understanding of the device workings and careful specification of the test variables are required both to analyze the data correctly and to permit comparison between data sets. It is concluded that the device is a useful and versatile field quality control and pavement investigation tool if an understanding of the device issues is considered by data users.

Assessment of In Situ Dielectric Constant of Pavement Materials

The use of ground-penetrating radar (GPR) for pavement investigation has developed rapidly over the past 20 years. The technique involves recording the passage of electromagnetic pulses transmitted into the pavement structure. GPR has enhanced and improved the range and certainty of information that can be obtained from pavement investigations. Analysis of data can provide information on layer depths, material condition, moisture, voiding, reinforcement, and location of other features. The dielectric constant is a material property that affects the speed and reflection amplitude of electromagnetic GPR pulses. Accurate determination or estimation of the dielectric constant is required for accurate analysis of pavement material information from GPR data. Typical pavement materials will have a bulk dielectric constant used in analysis that is the result of both the material constituents (binder, aggregate, etc.) and condition (moisture content, amount of voiding, etc.). This paper aims to provide a review and assessment of in situ dielectric constants of bituminous pavement materials determined from analysis of GPR data. The results of a large number of in situ pavement investigations, on a range of bituminous materials of varying condition, are reported. Dielectric constants from analysis of GPR investigations are determined and compared with existing data, and the effect of material condition and properties are discussed and assessed. The paper concludes that improved assessment of the in situ dielectric constant can be conducted and provide enhanced information from radar data analysis if consideration of material condition is made when selecting the values used in the analysis.

Environmental and Sustainability Impact Assessment of Infrastructure in the United Kingdom

Sustainability, now embedded within the legislation and development policy of the United Kingdom, is beginning also to be implemented within the design and construction process. Methods to assess the sustainability of construction projects have been in development since the early 1990s, but to date the majority have focused on the building sector, with little consideration for the detailed assessment of civil engineering projects. In addition, the tools developed have rarely considered sustainability in its widest sense, instead concentrating on the more quantifiable aspects of the environment, ecology, and building material use. The U.K. civil engineering industry has attempted to fill this gap with the development of the Civil Engineering and Environmental Quality Assessment and Award Scheme (CEEQUAL). The use of CEEQUAL is voluntary, but it is seen as a benchmark for assessing the environmental and social impact of infrastructure. Background to sustainability assessment for projects in the United Kingdom and the development of CEEQUAL and areas for improvement are presented. The paper then presents the results of a backanalysis for three infrastructure projects, with CEEQUAL to assess the design teams’ compliance with and comprehension of sustainability issues within their projects. Although infrastructure design teams are likely to engage with sustainability issues in assessment areas in which they have previous experience (such as environmental impact and biodiversity), more education is required to encourage increased awareness in the relatively new areas of design assessment, including minimizing carbon footprint, material specifications, and material use and reuse.

Sustainable Earthworks Specifications for Transport Infrastructure

The specification of the materials and methods used in earthworks and foundations for highways, railways, and airfield runways can be approached in several ways. There is a need for a more sustainable use of resources, and specifications that make best possible use of material properties are required. A performance-based approach is considered the best way to achieve this. The functional requirements of a performance-based specification for UK highway foundations were considered. The recently researched performance-based specification, demonstrating the steps to its development, determination of the engineering requirements, suitable target values, and potential construction-related implications, is explained. Performance-based specifications offer the advantage of better incorporation of the principles that underpin sustainable construction and require a fuller understanding of material behavior for their development and implementation. However, contractual issues and implications for construction need t...

Framework for Carbon Emission Evaluation of Road Maintenance

In the United Kingdom, carbon emissions associated with business activities have shifted from matters of policy to sources of legal responsibilities under the Climate Change Act of 2008. A flexible and easy-to-use technique is needed so that businesses can assess their carbon emissions in response to regulations on the environmental impact of construction activities. The aim of this study was to develop a methodology that could offer businesses a carbon life-cycle assessment tool to identify emissions hot spots across the value chain and inform a carbon-reduction hierarchy. The approach employed was based on methodology described in the publicly available specification (PAS2050) protocol. The objective was to identify locations where the largest production of emissions occurred and provide for the biggest potential reduction within routine highway maintenance processes. The methodology framework allows businesses to make informed decisions in carbon terms through the identification and prioritization of areas of potential reduction of emissions.

Development and Implementation of a Lifecycle Carbon Tool for Highway Maintenance

AbstractThe highway maintenance sector within the United Kingdom consumes considerable amounts of natural resources and accounts for a large amount of carbon emissions. Carbon emissions reduction is now considered an integral part of tender selection criteria and project performance issue by highway clients. This requires contractors to be able to assess and reduce both direct and indirect emissions associated with highway maintenance. This presents a challenge for the sector as despite the availability of methods to assess carbon there are no routine tools to allow a lifecycle assessment (LCA) approach to carbon reduction as part of ongoing maintenance management. Thus, there is a need for a consistent, project-focused carbon assessment tool, underpinned by a robust LCA methodology that can assess emissions and emissions reduction across core highway maintenance processes. This paper describes the development and business implementation of such a tool based on the Publicly Available Specification (PAS) 2...

A Case Study of the Introduction of a Workplace Parking Levy in Nottingham

Abstract Purpose A Workplace Parking Levy (WPL) scheme represents a major transport demand management intervention which raises a levy on private non-domestic off street parking provided by employers to employees, regular business visitors and students. It therefore increases the average cost of commuting by car and stimulates a contraction in the supply of workplace parking places. Under UK legislation the revenue from such a scheme is hypothecated funding for further transport improvements. As such it is potentially an important mixed policy instrument available to transport authorities to tackle traffic congestion and create extra transport capacity by using the additional funding such a scheme provides. At present, in the United Kingdom, only Nottingham City Council has implemented such a scheme and thus an understanding of how that scheme was implemented, how it operates and the outcomes after a full year of operation are of importance to transport academics and other local authorities considering utilising a similar approach. Methodology This chapter presents an overview of the WPL scheme in Nottingham. The legislation, implementation experience, monitoring framework and outcomes for this scheme after the first year of full operation are discussed by drawing on current literature, documentary evidence and monitoring data. Findings The Nottingham WPL scheme was fully implemented in April 2012. The gap between the provisions of the underpinning legislation and the functioning scheme has necessitated the formulation of policy in line with the spirit of the legislation. Acceptance by the business community and the public were further barriers to implementation which were mitigated by a consultation process and a Public Examination. However acceptance remains a concern until the scheme has been shown to meet its key objective of reducing congestion. To date there is no evidence that the scheme has had a negative impact on business investment and, while there is as yet no evidence traffic congestion has reduced, it is still early for such impacts to be identified especially as the majority of the associated public transport improvements are yet to be implemented. However the WPL has already raised £7 million in net revenue in its first year of operation which is hypothecated for public transport improvements which may help encourage inward investment and reduce car travel. Practical implications At present the Nottingham WPL scheme has only been operational for a short time and a limitation to the research presented here is that the major public transport improvements part funded by revenue hypothecated from the WPL are not yet in place. It will be necessary to wait at least a further 3 years before more definite conclusions as to the success of the WPL package can be drawn. Originality/value of the chapter As the first of its kind in the United Kingdom or indeed in Europe, the WPL scheme in Nottingham provides a unique contribution to the literature, comparing and contrasting implementation and outcomes with those in Australia and Canada. Geographical and cultural differences between the United Kingdom and these countries mean that conclusions drawn concerning existing schemes in other continents are not necessarily transferable to the United Kingdom. This chapter provides evidence in a UK framework to assess if the approach could be suitably applied more widely.

Assessing the influence of moisture on the dielectric properties of asphalt

The presence of moisture in asphalt can reduce the cohesion between binder and aggregate, and can thus lead to premature deterioration of the pavement structure. This issue is particularly relevant in the UK, as well as other areas around the world, where records suggest climatic trends showing increased total rainfall, and increased frequency of periods of very wet weather. Detection of locations where excessive moisture may be present, or where moisture ingress may be occurring, is important for the maintenance of asphalt pavements. The dielectric properties of asphalt are heavily influenced by the amount of water in the material. Data from ground penetrating radar (GPR) investigation can be used to estimate asphalt dielectric properties, and hence to assess areas of relative moisture content, although it is often difficult to quantify absolute moisture amounts. This paper describes a series of laboratory tests conducted using asphalt core samples taken from road pavements, to establish the relationship between moisture content and the dielectric values determined from GPR data. It has been possible to observe and quantify the asphalt dielectric constant as it changes as a result of changing moisture content. The results of this study can be used to improve estimates of moisture amounts from GPR data obtained from asphalt pavements, and to quantify the effect on dielectric values that increases in moisture content may produce. The findings from the work can assist in producing more confident and accurate outputs from GPR pavement moisture investigations.

Assessment of performance specification approach for pavement foundations

Road foundations are currently designed using established empirical relationships and a recipe specification, according to which specified materials are laid and compacted using specified methods. Such an empirically based specification is unlikely to result in an efficient use of construction equipment or materials and does not allow the use of analytical design procedures. If a move to a performance specification can be adopted, functional subgrade and foundation material parameters can be used in design and compliance testing. This allows for the use of previously untried materials and provides assurance of the “as-constructed” performance of the pavement foundations. The philosophy adopted for a performance specification currently being researched in the United Kingdom is explained. The performance parameters to measure for both design and compliance testing, and when they should be measured, are detailed. The requirements of tests to measure the parameters are specified, and the techniques currently available are reviewed. Finally, selected results from field trials performed to evaluate the proposed specification are presented. Research has shown that techniques are available to allow for a move to a performance specification. However, the assessment of granular materials with large particle sizes requires further research. The trials revealed that adequate compaction of subbase can be achieved on a wider range of supporting materials than might be expected. Significant variability in test data was found for small areas of the same site containing similar subgrades; therefore, any target values set for compliance testing should be ideally both material and site specific.

PROCEDURES FOR ESTIMATING ENVIRONMENTAL IMPACT FROM RAILWAY INDUCED VIBRATION: A REVIEW

Railway induced ground-borne vibration is among the most common and widespread sources of perceptible environmental vibration. It can give rise to discomfort and disturbance, adversely impacting on human activity and the operation of sensitive equipment. The rising demand for building new railway lines or upgrading existing lines in order to meet increasing transit flows has furthered the need for adequate vibration assessment tools during the planning and design stages. In recent years many studies in the fields of rail and ground dynamics have encouraged many prediction techniques giving rise to a wide variety of procedures for estimating vibration on buildings. Each method shows potential for application at different levels of complexity and applicability to varying circumstances. From the perspective of railway environmental impact assessment, this paper reviews some relevant prediction techniques, assessing their degree of suitability for practical engineering application by weighting their methodology (i.e. considerations and requirements) against practicality and precision. The review suggests that not all procedures are practicable (e.g. the attainment of representative parameters needed to run the procedures) whilst others predicate on assumptions, which revealed to be too relaxed resulting in insufficient accuracy; however, a combination of methods may provide the necessary balance.Copyright