Mechanical properties of adobe walls in a Roman Republican domus at Suasa

Adobe is a construction technique that uses raw earth mixed and moulded to form sun-dried blocks to realize a bearing wall. The recent discovery of adobe walls belonging to a Republican domus sited in Suasa (Ancona, Italy) was the starting point of the present work. The research was developed through an experimental approach, in order to characterize the mechanical behavior of this type of walls: firstly some adobe blocks similar to the original ones were reproduced by using the soil directly came from the archaeological site near the adobe walls and adding straw to reduce hygrometric shrinkage and coarse sand, taken from a local quarry, as a stabilizer, as Romans were used to do. Then, after a seasoning period of 4 months, four adobe walls were produced to be tested by compression and shear. From compression tests, maximum strength, first cracking compression stress, Young modulus and breaking manner were evaluated. As well, compression results show a possible two-storey structure of the earthen Republican domus. In fact, it appears that the stress from the two-storey load analysis is lower than the first cracking compression stress. From the shear tests, a proportional law seems to regulate the relation between the maximum value of the mean tangential tensions and the vertical compression the sample is subjected to. This could be the starting point for a future seismic analysis.