Optimum water content tests for earthen construction materials

There is considerable interest in earthen construction materials, owing to their inherent sustainability, and also in the conservation of heritage structures. For new-build in situ construction a key aspect of quality control is the achievement of full compaction to maximum dry density. At present the guidance available in this area to those using these materials varies from British Standard tests to heuristic-based methods developed by practitioners. In this paper, the various tests are compared for different soil mixes and also to judge the influence of the test operator. The study demonstrates shortcomings in the heuristic methods and indicates that, for modern standards of quality control to be achieved, alternative tests should be used.