Specification development for the use of Devon cob in earthen construction
The traditional earthen building practice of cob construction has been historically linked to Devon for many centuries. However no standards or specifications exist to facilitate a technical appraisal of the material. This thesis sets out to develop an appropriate test methodology for the classification and compressive strength determination of Devon cob. The absence of appropriate standards for cob construction is shown as a function of neglect for Devon cob as a potential construction material. National and international events that have re-kindled interest in earth as a building material are discussed, with particular reference to cob construction. A rationale is presented to justify the selection of the soils used in the experimental program. The utilisation of 'soil surveys' to inform selection of suitable cob building is found to be hindered by a lack of modernisation in terms of data presentation. A definitive test methodology is presented and used in the determination of unconfined compressive strength for cobs formed from the selected soils. While the addition of straw is shown to influence the strength of soils, its influence is clearly matrix specific. The pressure membrane test is presented as a suitable means of classifying cob fabrics at a microstructure level. These findings offer new insights into Devon cob.