Alternative stabilised rammed earth materials incorporating recycled waste and industrial by-products: Life cycle assessment

Abstract

As the Paris Agreement target year of 2030 draws nearer, it is becoming increasingly evident that neither Australia nor many other nations are progressing at a rate sufficient to meet greenhouse gas emissions targets. One area in which to improve performance is in the use of low embodied energy construction materials. Rammed earth (RE) is often considered to be one such material. However, many modern RE variations incorporate cement: a significant contributor to global CO2 emissions. RE materials with low greenhouse gas emissions have been developed as replacements for conventional construction materials. In this series, we examine the strength development, durability and sustainability, via life cycle assessment, of these new materials.This paper explores the cradle-to-gate greenhouse gas emissions of RE materials incorporating recycled waste (crushed brick and concrete), industrial by-products (ground granulated blast furnace slag, fly ash and silica fume) and either NaOH or hydrated lime. These are then compared to construction techniques conventionally used in Australia (cavity brick and brick veneer). Attributional life cycle assessments were carried out for hypothetical building envelopes suitable for climate zones 1–7, assuming construction in metropolitan Perth and 600 km inland (Kalgoorlie, WA). Results showed that greenhouse gas emissions per vertical square metre of wall could be reduced by 73% or 57% respectively when compared to traditional cavity brickwork or brick veneer. This is in contrast to RE incorporating cement, which produced a saving of just 15% compared to brick veneer. If this construction technique were adopted across Australia for new, detached dwellings constructed during 2021–2030, this could represent a greenhouse gas reduction of 11.3 million tonnes CO2eq, or 1.2–1.3% of the cumulative emissions reductions required in 2021–2030 to meet Australia’s Paris Agreement targets.