Structure, Design and Applications of Geopolymeric Materials

The term “geopolymer” was firstly applied to describe a family of alkaline aluminosilicate binders formed by the alkali activation of aluminosilicate minerals. The formation of geopolymeric materials is the result of a complicated heterogeneous chemical reaction occurring between Al-Si solid materials and strongly alkaline silicate solutions. The geopolymerization reaction is exothermic and takes place under atmospheric pressure at temperatures below 100C. Despite of the intense research on the geopolymerization of different aluminosilicate materials and the development of a wide range of geopolymeric materials, the exact mechanism that takes place during geopolymerization is not fully understood. The most proposed mechanism for geopolymerization includes the following four stages, which proceed in parallel and thus, it is impossible to be distinguished: (i) Dissolution of Si and Al from the solid aluminosilicate materials in the strongly alkaline aqueous solution. (ii) Formation of Si and / or Si-Al oligomers in the aqueous phase. (iii) Polycondensation of the oligomers to form a three-dimensional aluminosilicate framework. (iv) Bonding of the solid particles into the geopolymeric framework and hardening of the whole system into a final solid polymeric structure. This paper will describe in detail the structure of the geopeolymeric materials, the parameters that has to be taken into consideration for their designing and their potential applications.