Geopolymer Stabilisation of Unfired Earth Masonry Units
Contemporary domestic structures typically use masonry units that are approximately 100mm thick. There is interest in using commercial methods of manufacture to produce earthen bricks that have a similar form factor to conventional masonry The large scale adoption of thin walled unfired earth masonry is dependent on its suitability for use in a load bearing application. High moisture content leading to full saturation, for example as a result of flooding, is a concern for unstablised earth construction, especially as wall thickness reduces. The greatest barrier for earth masonry adoption is the durability of the material when affected by high moisture content. Accidental and intentional wetting of a 100mm thick load bearing unfired earth wall could lead to disproportionate collapse. The paper presents initial findings from an investigation into the use of geopolymer mechanism as a method of stabilisation. The use of geopolymer mechanism was chosen as a possible method of improving the water resilience. Soil that is used for commercial extruded fired brick production was chosen. The soil was selected as the precursor (source of the required silica and alumina) and this was mixed with various sodium hydroxide and sodium silicate activators. Specimens were tested both in their dry sate as well as following 24 hours of submersion in water. Compressive strength of cylinders after saturation, was used as an indicator of effective stabilisation. The maximum dry compressive strength achieved was 10.4N/mm2 with the addition of 5% sodium hydroxide and 20% sodium silicate after curing at 105°C. The most significant contributor to the strength gain was the addition of sodium silicate. Although some of the cylinders were able to be tested under fully saturated conditions the strengths achieved were negligible and insufficient for structural application. The potential for geopolymers as a method of stabilising unfired earth bricks is discussed with respect to the compressive strengths achieved.
Prof. Khosrow Ghavami, Normando Perazzo Barbosa and Alexandr Zhemchuzhnikov
D. Maskell et al., "Geopolymer Stabilisation of Unfired Earth Masonry Units", Key Engineering Materials, Vol. 600, pp. 175-185, 2014