The authors say that “Davidovits reported that geopolymers possess high early strength, better durability and has no dangerous alkali-aggregate reaction”. However, other authors have a different opinion. Workability in geopolymers is poor and not easily adjustable due to a sticky and thick mortar that is generated during processing. This means that the traditional construction industry practices cannot be used for geopolymeric cements. Also the alkaline and soluble silicates that are added during the processing cannot be totally consumed during geopolymerization due to the existence of dissolution equilibrium of raw aluminosilicate in alkaline silicate solutions and this causes severe efflorescence of the final geopolymer products and high porosity and permeability due to the movement of alkali together with water to the geopolymer surfaces (Zheng et al., 2007). Zheng D., Van Deventer J.S.J., Duxson P., “The dry mix cement composition, methods and systems involving same”, International Patent WO 2007/109862 A1, 2007.

Lloyd (2009) found that for instance metakaolin based geopolymers show a relevant strength loss that makes them unsuitable for construction purposes. Also Lloyd et al, (2010) showed that geopolymers are prone to alkali leaching that could lead to a rapidly and disastrous reduction in the pH causing steel corrosion. They stated that it is not certain how long a steel reinforced geopolymer structures will be able to resist corrosion. Lloyd, R. Accelerated ageing of geopolymers. In Provis and Van Deventer (Ed.) Geopolymers: Structure, processing, properties and industrial applications. CRC Press. 2009; 139–166. Lloyd, R.; Provis, J.; Van Deventer, S.J.S. (2010) Pore solution composition and alkali diffusion in inorganic polymer cement. Cement and Concrete Research 40, 1386-1392.

The authors say that “Geopolymers are cementitious materials that do not depend on the presence of calcium” However, Van Deventer et al. (2012) have show that calcium is crucial for the strength and durability of geopolymers. van Deventer, JSJ,; Provis, JL; Duxson, P. (2012) Technical and commercial progress in the adoption of geopolymer cement. Minerals Engineering 29, 89–104.