State of the Art: Europe
Rowland Keable and Martin Rauch, two leading rammed earth practitioners in England and Austria respectively, both claimed in independent interviews and site visits during June 2005 that the addition of portland cement was unnecessary in a properly detailed rammed earth structure if the natural clay content was high enough in the soil used for compaction. This claim is especially impressive in the case of Rauch, whose projects in high alpine regions of Austria and Switzerland must withstand annual precipitation exceeding that of New England, and more extreme wintertime temperatures. Rauch has experimented with augmenting natural clay content of the soil with other sources of clay to achieve the desired ratio. Keable has also experimented with a number of different materials, including walls of rammed chalk at the Pines Calyx project in Dover, England where the chalk occurs naturally at the project site.