Inorganic stabilisation methods for extruded earth masonry units

Abstract

Addressing the challenges of embodied environmental impact of materials has led to growing interest in the use of earth as a construction material. Adopting large-scale commercial methods of extruded brick production has potential to overcome many of the existing barriers of adoption. Without the firing the bricks will have a significantly lower embodied environmental impact and similar dimensions (just over 100mm thick in the UK) to conventional masonry. However, the wider adoption of 100mm thick unfired earth masonry is dependent on its suitability for use in structurally load-bearing applications. Currently the greatest barrier to earth masonry adoption is the durability of the material when subjected to high moisture contents. Accidental or intentional wetting of a 100mm thick load bearing unfired earth wall could lead to disproportionate collapse unless the moisture resistance is improved.To overcome the concern of elevated moisture contents, a common approach is to chemically stabilise the soil using either cement or lime. While there has been research into the use of cement and lime for other forms of earth construction, their use for extruded earth bricks has not been investigated in depth. The source materials and inherent physical properties of extruded earth bricks are different to other forms of earthen construction. Therefore the suitability of cement and lime to stabilise soil for the purpose of extruded earth bricks requires investigation.This research demonstrates the improvement in 28day compressive strength, with a range of cement or lime contents and three initial curing temperatures. Small scale bricks were tested in both the ambient environmental conditions and following 24h of full submersion in water. Key factors, such as density and moisture content, are shown to be important for compressive strength development. The effect of stabilisation has been shown to be more important as a determinant for strength than density and moisture content alone.