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Title: Carbon Dioxide Emissions due to Highway Subgrade Improvements
Accession Number: 01126770
Record Type: Component
Record URL: Availability: Transportation Research Board Business Office 500 Fifth Street, NW Find a library where document is available Abstract: Improving poor subgrades is essential to facilitate highway construction and ensure long-term stability. Improvements include enhanced load distribution by using crushed rock “capping” layers or increasing the subbase thickness if the bearing capacity of the subgrade remains unchanged, and lime stabilization of soft clay subgrades improves the subgrade stiffness and strength to reduce or remove the need for additional crushed rock. However, the relative sustainability of subgrade improvement options as determined by indicators such as carbon dioxide (CO2) emissions is not immediately apparent. If capping is used, the relative depth requirements, together with variations due to different aggregates, make the lowest emissions option unclear. Lime production incurs far greater CO2 emissions than aggregates production, but it is used in smaller quantities and the quantity truly required, as opposed to that commonly specified, requires consideration. To address these decision-making dilemmas, a methodology is presented that allows the relative sustainability, according to CO2 emissions, to be evaluated. This methodology is illustrated through analysis of available improvement options for a typical low California bearing ratio clay subgrade by using capping, subbase thickening and lime stabilization, or a combination of these solutions. It is concluded that analysis of the relative sustainability of subgrade improvements can be informed by emissions calculations and that the lowest emissions option is heavily dependent on associated highway haulage vehicle movements. However, wider appreciation of financial, social, and environmental factors and a fundamental understanding of the role of lime stabilization are necessary if road foundations are to be constructed sustainably.
Monograph Title: Monograph Accession #: 01140575
Report/Paper Numbers: 09-2769
Language: English
Authors: Rogers, Christopher D FThomas, Andrew MarkJefferson, IanGaterell, MarkPagination: pp 80-87
Publication Date: 2009
ISBN: 9780309126199
Media Type: Print
Features: Figures
(4)
; References
(18)
; Tables
(1)
TRT Terms: Uncontrolled Terms: Subject Areas: Construction; Environment; Geotechnology; Highways; I15: Environment; I51: Earthworks and Soil Drainage
Files: TRIS, TRB, ATRI
Created Date: Jan 30 2009 7:07PM
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