From common clays to Geopolymer binders - crystallographic and building material technology-based investigations

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Up to date actual scientific knowledge about the thermal and alkaline activation of common clays is restricted to a phenomenological description, despite common clays being the most heterogeneous, natural raw materials in terms of their phase content, structure and particle morphology. However, due to their chemical and mineralogical composition as well as for the future availability they seem to be particularly suitable for an alkaline activation, and thus, for the development of Geopolymer binders. Currently, the relation between material properties and process parameters for common clays has not been investigated with respect to the resulting properties of mortars and concretes based on Geopolymer binders. One approach to gain a better understanding of these phenomena is the combination of investigations of model clay minerals and real common clays, which will be the main focus of this research project. The focus of this study will be on the investigation of the occurring reactions when using calcined common clays as an alkaline activation source material for the production of Geopolymer binders dependent on phase content and crystal structure of the clay minerals. Most attention will be paid on the interaction between metaclay minerals and thermally not activated clay minerals in order to predict the raw material behaviour of the naturally occurring clay mixtures on a performance basis. In addition, fundamental knowledge about the activation and reactivity of metaclay can be derived from these investigations which could be also considered in cementitious mortars and concretes where calcined clays are used.Furthermore, Geopolymer binders and mortars are initially in the center of interest, due to the complexity of these systems. By the applicants approach strong and fundamental statements about texture, porosity/permeability, surface structure, alkalinity and selected mechanical properties of Geopolymer binders and mortars made of calcined common clays, can be systematically derived for the first time generated by means of natural and engineering science methods. The project objectives shall be achieved by two interacting working packages, which deal with mineralogical and crystallographical characteristic values, process parameters and construction material technological properties of Geopolymer binders and mortars.