Appropriate structural unfired earth masonry units

Abstract

Modern earth masonry utilises conventional methods of extruded fired brick manufacturing for the manufacture of unfired earth bricks. However, the bricks produced currently are not generally recommended for structural applications due to their loss of strength under elevated moisture content. In response to this loss in strength, bricks can be chemically stabilised, typically by the addition of cement or lime. However, the use of such binders typically negates the reduced environmental impact of using unfired brick, which is often the initial driver. The research presented in this paper considers the improvement in compressive strength that can be achieved through the addition of a range of pozzolanic binders as well as their associated embodied energy and carbon dioxide. This allows for a holistic comparison of material selection based on meeting the minimum structural requirements of the masonry units, while improving the embodied impact of equivalent units currently used. The study shows that an unfired brick with the addition of lime and metakaolin achieves a compressive strength of more than 6 MPa when dry and more than 1 MPa following complete saturation, while reducing the global warming potential by more than 30%. This paper demonstrates that stabilised unfired bricks can be practically viable, structurally suitable and environmentally beneficial.