Evaluating Reuse Opportunities for Recovered Building Materials
This is a partially developed activity description. It is included in the collection because it contains ideas useful for teaching even though it is incomplete.
Summary
In this activity, students investigate opportunities to reuse recycled building materials as a substitute for the use of virgin stone, sand and other mined materials routinely used in construction. As an example, recycled asphalt, brick and concrete, may, if properly processed, become an appropriate substitute sub-base material for crushed stone aggregate. Such a substitution may have a significant impact on a project's carbon footprint and overall environmental impact in a number of ways, which are explored and quantified in the activity. The feasibility of substitute materials from an engineering performance perspective is also investigated. Finally, perceived or actual impediments to promoting and implementing specific recycling opportunities are identified which may include regulatory acceptance, current construction means and methods, and the existence and accessibility of recycling markets.
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Learning Goals
- Understand and apply concepts of building material characterization, standard testing methods of aggregate and engineering properties of building materials.
- Become familiar with material specifications in construction and performance specifications in construction design.
- Become familiar with the regulatory process of developing performance specifications as well as the permitting process.
- Understand and apply concepts of life cycle analysis to building materials in terms of energy loads, environmental impacts and design life costs.
- Depending on the course-specific use of this activity, students may develop and apply communication skills through written report writing, an oral presentation and/or communicating with government staff and practicing professionals.
Context for Use
The activity is envisioned as a semester-long group project that is performed parallel to topics covered in an environmental science or engineering sustainability course, but the concept could be adapted to other science or policy/planning based courses. The project would incorporate concepts of: aggregate and engineered material properties, including compaction, strength and reactivity; building and road design code and regulations; and energy, environmental and economic life cycle assessment. Feasibility of specific recycling opportunities is determined based on economic and environmental analyses.
This activity is currently planned for an upper level undergraduate course and students should have some exposure to materials science and economics, though it is believed that that scope of the activity could be modified to be offered at a higher (graduate) or lower (to high school) level.
Description and Teaching Materials
First, the recycled reuse opportunity needs to be identified. For example, consider the use of crushed concrete as a substitute sub-base material for ¾ inch crushed stone used for a sidewalk as specified in a Town's sub-division regulations. Sub-division regulations for a municipality are needed and in most cases are posted online and readily accessible.
Next students compare and contrast the physical and chemical characteristics as well as the structural properties of the specified stone to concrete. This information is available in construction material resources such as standard texts.
The performance criteria of the sidewalk are examined. This information is available in state/federal code and/or other engineering design resources and may be further investigated based on setting-specific loads and conditions.An energy life cycle assessment is performed. The embodied energy of each alternative material is evaluated using established estimation methods, including comparing the site-specific differences in transporting recycled concrete (presumably local) to transporting crushed stone (presumably not local) to the construction site. Similarly, a life cycle assessment of the environmental impacts of the two materials is performed.
Costs, normalized to the design lives of each alternative, are compared in an economic analysis.
The feasibility based on energy consumption, environmental impact and costs is determined for the two alternatives.Finally, any regulatory acceptance, market availability and other relevant issues that may affect the analysis is identified.