Both in developed and developing countries, modern building materials tend to be preferred to traditional earthen construction. Reasons include low durability, inadequate performance under seismic loading and, in developing countries, a wish to replace what is perceived as 'poor' with what is perceived as 'rich'. In an age when building permissions and construction standards are a must, particularly in seismic areas, even when an owner is willing to build in earth, construction approval needs to be granted: we rely on values and standards to build, but the necessary data on material properties and structural performance of earthen building techniques is scarce if compared to the abundance of data for other materials (clay brick masonry, concrete, steel) available to the engineer. At the same time, traditional builders' skills, knowledge and confidence in earthen building techniques are decreasing if not disappearing. A wallette testing campaign was thus carried out with the aim of filling this knowledge gap. Prior to the wallette campaign, material properties, including composition and physical-mechanical parameters, were determined. Compression and diagonal compression (shear) tests were then performed, and a basic analysis of the mechanical behaviour of structural elements built in cob is provided in relation to earth block (adobe) masonry and rammed earth elements. Cob, shown to have low compressive resistance, has a relatively ductile post-peak behaviour if compared to earth block masonry specimens which, as expected, show a marked brittle behaviour. In terms of shear strength, cob performs relatively well in view of its low compressive strength. The study is part of our work within the framework of the ongoing project NIKER funded by the European Commission dealing with improving the structural performance of Cultural Heritage assets in order to limit earthquake hazards.
In August 2013, the German National Institute for Standardization DIN published three national standards for industrially-produced earth building materials without the use of chemical stabilizers:
DIN 18945 Earth blocks definitions, building materials, requirements, test procedures DIN 18946 Earth masonry mortars definitions, building materials, requirements, test procedures DIN 18947 Earth plaster mortars definitions, building materials, requirements, test procedures The development of these standards was initiated by the Dachverband Lehm e.V. (DVL), the German umbrella organisation for building with earth. These standards are in accordance with the requirements of the EU Regulation No. 305/2011 which came into force in Germany on 1 July 2013. These basic requirements introduce provisions relating not only to the safety of buildings and other construction works but also to health, durability, energy economy, protection of the environment and other important aspects in the public interest. The basic requirements are defined by essential characteristics expressed by levels or classes, or in a description. The relevant essential characteristics define the performance of the construction product.
The DIN 18945, 46 and 47 outline unified test procedures describing the relevant essential characteristics of the earth building products as well as systems for assessing and verifying the constancy of their performance. The relevant systems of verification are determined by a national Technical Assessment Body (TAB), which in Germany is the Deutsches Institut für Bautechnik DIBt.