The use of clay plasters with or without plant fibers (straw, hemp or other) inside buildings is currently showing considerable growth in many countries. Despite this development, there are very few data in the literature on the characteristics of clay plasters. This paper deals with the characterization of five ready-mixed clay plasters from French brickworks using the recent German standard. The work essentially consisted in measuring the flow of fresh clay plasters and their characteristics after hardening (shrinkage, and compressive, flexural and adhesive strength). The characterization of the samples showed that the granular characteristics were practically the same and that the main difference concerned the nature of the clayey minerals they contained: four samples were essentially composed of montmorillonite, chlorite and illite whereas one was only composed of kaolinite. Despite this difference, the flow of fresh clay plasters and their characteristics after hardening (shrinkage, compressive and flexural strength) were very similar and were comparable to the values given by the standard. However, the measurement of the adhesive strength led to two significant problems: the dispersion of the values was very high and the results were markedly different from the values given by the standard. For these reasons, it seems necessary to complete and adapt the procedure for measuring adhesive strength and it could be interesting to develop new tests for the measurement of this important characteristic, either in the laboratory or on building sites.

This is the accepted author's version of an article protected by copyright. The rights are held by Springer-Verlag Wien.The final publication is available at http://link.springer.com. Summary During the crossing of brittle rock formations at the Lötschberg base tunnel, failure phenomena have been observed both at the tunnel face and at the walls. A detailed analysis has been undertaken to explain these behaviours, based on the recent developments of Canadian research on brittle failure mechanisms. At the tunnel walls, a very good agreement is found between calculated and observed damage and between two prediction methods i.e. a semi-empirical failure criterion and elastic calculations with the "brittle Hoek-Brown parameters". Near the face, due to the 3D nature of the stress conditions, some limitations of these approaches have been highlighted, and the growth of wall failure has been analysed. This research allowed a better understanding of the brittle rock mass behaviour at the Lötschberg base tunnel and showed that brittle failure processes dominate the behaviour of deep, highly stressed excavations in massive to moderately jointed rock. It also illustrates where improvements to the adopted approaches are required.

In the European Union, most of the wastes from the building sector are composed of earths. Earth construction may be an interesting outlet for the re-use of these wastes, while meeting the challenge of circular economy: in particular, it involves low-embodied energy processes and earth material can be re-used for building by end-of-life. Nonetheless, the identification of suitable earths for construction remains an issue. To overcome this problem, an option may be to analyse earth building heritage, which is at least one-century old in Europe: indeed, earth employed in these buildings can be regarded as "time-tested", and thus suitable for construction. In this paper, more than 20 different earths collected in rammed earth heritage building in France are presented. The results are confronted both to literature and to several classifications employed in soil sciences. A classification system based on granularity and clay activity will be relevant to address the convenience of earth for building purposes.

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