Geopolymers polymerization reactions

The alkali silicates is one of the raw materials classically used in the formulation of new materials like geopolymers. Geopolymers are amorphous three-dimensional aluminosilicate binder materials which are synthesized at ambient temperature by the alkaline activation of silica solution and aluminosilicates derived from natural minerals, calcined clay or industrial byproducts. Previous study focused on the aluminosilicate sources have shown that the presence of impurities and the reactivity of the metakaolin (aluminosilicate source) can lead to the formation of one or several networks in geopolymers materials [1]. Indeed, the different sources of metakaolins conduct to the presences of various siliceous species in the solution which react with alumina. These multiple combinations lead to the formation of different networks (then various properties of geopolymers). To understand the formation of these various networks, studies relative to the neutralization of siliceous species in solution have been done. Parmentier [2] showed that the ammonium molybdate could react with silica to create silicomolybdic compounds. More recent studies demonstrated that ammonium molybdate could also react with these species in an alkaline environment [3]. These analyses showed that ammonium molybdate could react not only with monomers and dimers, but also with larger molecules. According to this, molybdate can permit to complex siliceous species and to modify polymerization reactions. The aim of the study is to study the influence of the ammonium molybdate addition on the kinetics of the polycondensation reaction as well as on the formation of several networks. 

Transformation of the initially deposited remains of living organisms started in the water columns and in the upper layers of bottom sediments of ancient seas. Random polymerization and condensation reactions of degraded biopolymers are believed to have formed the initial geopolymers, which contain humin, fulvic and humic acids. Until now these compounds (very typical for soil humus as well) are... 

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