Weathering the storm: A framework to assess the resistance of earthen structures to water damage

Earth building is experiencing a renaissance due to the emerging recognition of the damage the construction industry is doing to the global environment. Research over the past three decades has identified the hygroscopic nature of these materials, and our understanding of the factors governing their hydromechanical properties is now mature. However, little work has been done to unify methods to assess material durability: namely, how exposure to degrading agents, predominantly water, impacts a structure's service life. Although strength is usually of primary concern to engineers, it is undeniable that earthen structures usually fail due to durability, rather than strength, issues. As earthen architecture and demands made of the material become more ambitious, the need for robust guidelines on how to predict the longevity of these structures becomes paramount. This paper presents a framework for assessing the durability of earthen materials based on perceived routes of exposure to water. The framework is built upon the findings of a review of nearly 60 articles discussing original durability testing programmes, comprising 118 investigations and almost 700 soil and stabiliser combinations. From these works, 12 assessment methodologies were identified, encompassing a range of earthen construction techniques, e.g. mud brick, compressed earth blocks and rammed earth. Each method is described and its suitability for assessing the real world durability of a range of earthen construction techniques appraised. From this, the efficacy of each test was determined and a shortlist of suitable tests created. The derived framework provides assessors with a method to determine likely exposure routes for an earthen construction element (e.g. an internal or external wall) and, from the shortlisted methods, to specify the range of tests necessary to ensure suitable durability given the construction and environmental conditions. This work forms part of the update to the Standards Australia Earth Building Handbook: SA HB 195.