Life cycle analysis of environmental impact vs. durability of stabilised rammed earth

- Reducing cement content in SRE results in considerable emissions and energy savings.
- The use of waste materials is recommended to reduce the environmental impact of SRE.
- Consequential LCA results depend on the marketability of the by-product used.
- It is possible to have durable, strong and environmentally sustainable SRE mixes.
- Unconfined compressive strength should not be used as an indicator of durability.

Rammed earth (RE) has enjoyed a revival in recent decades due to the increasing awareness of environmental issues surrounding the building industry. Although RE in its traditional form is deemed a highly environmentally-friendly material, the same cannot be said for its modern stabilised counterpart. Comprehensive experimental procedures exist to estimate mechanical strength properties of stabilised RE (SRE). However, tests for material durability are far less common. Engineers and practitioners therefore assume that strength and durability are interchangeable properties, i.e. the stronger the material, the more durable. Inflated strengths are recommended to ensure adequate durability, leading to high environmental costs through excessive use of stabilisers.This paper rates the relevance of two acknowledged durability tests (accelerated erosion due to sprayed water and mass loss due to wire brushing) and relates outcomes to the strength and the environmental impact of several SRE mixes. The environmental impact of each mix was estimated using attributional and consequential life cycle assessment (LCA) approaches as well as an assessment of cumulative energy demand. Results demonstrated that it is possible to have durable SRE mixes without paying the cost of using environmentally-expensive stabilisers.

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