Date of Award

Spring 2009

Project Type

Dissertation

Program or Major

Civil Engineering

Degree Name

Doctor of Philosophy

First Advisor

Kevin Gardner

Abstract

The goal of this research was to broaden understanding of multiple impacts in assessing materials for construction. Life cycle assessment was used to this effect to understand the impacts from the use of industrial by-products for different applications on different spatial scales. The first two studies looked at applications in highway construction for a single project scenario and for a regional management scenario. The third study considered life cycle impacts for the management of construction and demolition (C&D) wood debris to include combustion for energy recovery. The fourth chapter reviews the literature for life cycle energy impact for building materials.

The first study found the use of bottom ash in place of crushed rock, on a regional scale, would result in a reduced energy and water consumption, reduced air emissions, reduced mercury and lead emissions and a reduced non-cancer human toxicity potential (HTP), but an increased HTP cancer due to contaminants leaching from the bottom ash into the groundwater. A fate and transport analysis however indicated that in this scenario these contaminants would not reach goundwater for over 200 years and in levels far below maximum contaminant levels.

The second study found the use of industrial by-products in combination with virgin aggregate in a regional management plan for roadway sub-base construction has lower life cycle impacts than the use of virgin aggregate alone, with the exception of HTP cancer. The HTP cancer values are highly conservative, not accounting for availability or fate and transport through sub-surface materials.

The third study indicated that combusting construction and demolition (C&D) wood for energy recovery has fewer environmental impacts than landfilling. A comparison of combustion of C&D wood versus virgin wood found the C&D wood scenario more favorable for all impacts with the exception of lead air emissions. However, lead air emissions for C&D wood still resulted in a reduction in emissions compared with the Northeast power grid.

The fourth study looked at the life-cycle energy (focused on the phases through manufacturing) of building materials, considering energy implications of recycling and material substitution, transport, and energy use compared to pre-use.

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