Moisture transfer and change in strength during the construction of rammed earth walls

A number of rammed earth projects constructed in recent years in Germany testify to the high level of architectural interest in this material in our country. Rammed earth has been “rediscovered” because of its unique materiality and fascinating and individual surface aesthetics, particularly by young architects. In connection with the realisation of two rammed earth projects realised in Thuringia in 2003/4 some questions arose concerning the processes of moisture transfer and changes in strength properties during construction. The earthen building standards document only very rough estimates of drying times for rammed earth walls. The idea arose to develop a test program for investigating the question of drying time with regard to the change in material strength in rammed earth walls, as well as for general aspects of testing procedures for rammed earth in standards. The paper presents first results of a laboratory program trying to approach to this very complex problem. A series of test specimens were produced and the unconfined compressive strength UCS were determined varying the drying times from 7 to 90 days. The moisture content of the test specimens was also varied: at OMC (PROCTOR test), lower and higher OMC.