The increasing interest on earth construction as a sustainable building solution led to the development of modern earth construction techniques, in particular of masonry made of compressed earth blocks (CEBs). The traditional chemical stabilisation of the soil is a frequently used improvement process. However, such process increases significantly the embodied energy of the CEBs. This paper presents an alternative technique for the stabilisation of CEBs, based on alkali activation of fly ash. The mechanical behaviour of the CEBs and of the respective dry stack masonry is comprehensively investigated through an experimental program, during which this technique proved to be highly effective.