Geopolymer Stabilisation of Unfired Earth Masonry Units


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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.



Edited by:

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

Online since:

March 2014




* - Corresponding Author

[1] Davidovits, J. (2008). Geopolymer chemistry and applications. Geopolymer Institute. ISBN: 9782951482012.

[2] Duxson, P., Fernández-Jiménez, A., Provis, J., Lukey, G., Palomo, A., & van Deventer, J. S. J. (2007). Geopolymer technology: the current state of the art. Journal of Materials Science, 42(9), 2917–2933.


[3] Habert, G., d'Espinose de Lacaillerie, J., and Roussel, N. (2011). An environmental evaluation of geopolymer based concrete production: reviewing current research trends. Journal of Cleaner Production, 19(11): 1229 – 1238.


[4] Heath, A., Goodhew, S., Paine, K., Lawrence, M., & Ramage, M. (2012b). The potential for using geopolymer concrete in the UK. In Press. Construction Materials.

[5] Heath, A., Lawrence, M., Walker, P., & Fourie, C. (2009). The compressive strength of modern earth masonry. In 11th International Conference on Non-conventional Materials and Technologies, NOCMAT 2009. University of Bath.

[6] Heath, A., Maskell, D., Walker, P., Lawrence, M., & Fourie, C. (2012). Modern earth masonry : Structural properties and structural design. The Structural Engineer, 90(4), 38–44.

[7] Heath, A., Walker, P., Fourie, C., & Lawrence, M. (2009). Compressive strength of extruded unfired clay masonry units. Proceedings of the Institute of Civil Engineers: Construction Materials, 162(3), 105–112.


[8] Khale, D. & Chaudhary, R. (2007). Mechanism of geopolymerization and factors influencing its development: a review. Journal of materials science, 42(3), 729–746.


[9] MacKenzie, K. J. D., Brew, D. R. M., Fletcher, R. A., & Vagana, R. (2007).

[10] Maskell, D., Heath, A., & Walker, P. (2013). Comparing the environmental impact of stabilisers for unfired earth construction. In NOCMAT 2013: 14th International Conference on Non Conventional Materials and Technologies.


[11] Maskell, D., Walker, P., & Heath, A. (2012). The compressive strength of lignosulphonate stabilised extruded earth masonry units. In Terra 2012: 11th International Conference on the Study and Conservation of Earthen Architecture Heritage.

[12] Morel, J. C., Pkla, A., & Walker, P. (2007). Compressive strength testing of compressed earth blocks. Construction and Building Materials, 21(2), 303–309.


[13] Morton, T. (2008). Earth Masonry: Design and Construction Guidelines. IHS BRE press. ISBN: 9781860819780.

[14] Morton, T. (2006). Feat of clay. Materials world, 14(1), 2–3.

[15] Rahier, H., Esaifan, M., Aldabsheh, I., Slatyi, F., Khoury, H., & Wastiels, J. (2011). Production of geopolymers from untreated kaolinite. In , Daytona Beach, FL, United states, 2011 (pp.83-89).


[16] Reddy, B. & Gupta, A. (2006). Strength and elastic properties of stabilized mud block masonry using cement-soil mortars. JOURNAL OF MATERIALS IN CIVIL ENGINEERING, 18(3), 472-476.


[17] Walker, P. (2004). Strength and erosion characteristics of earth blocks and earth block masonry. Journal Of Materials In Civil Engineering, 16(5), 497-506.


[18] Xu, H. & Van Deventer, J. (2000). The geopolymerisation of alumino-silicate minerals. International Journal of Mineral Processing, 59(3), 247–266.


[19] Xu, H. & Van Deventer, J. S. J. (2002). Geopolymerisation of multiple minerals. Minerals engineering, 15(12), 1131–1139.


[20] BS EN 196-3: 2005 (2005).