On The Mechanical Behavior of Metakaolin Based Geopolymers Under Elevated Temperatures

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Abstract
Geopolymers may be described as solid and stable synthesized aluminosilicate materials, whose properties are generally believed to provide a superior durability behavior. The work in hand presents the results of an experimental investigation on the thermomechanical behavior of geopolymer matrices composed by metakaolin (MK), silica fume (SF) and blast furnace slag (BFS). The alkaline activator solution consisted of sodium silicate and sodium hydroxide. The use of different aggregates was also investigated, by replacing natural sand with chamotte. Samples were submitted to different temperatures at predetermined intervals to a maximum of 1000ºC. Compression tests were performed, before and after the exposure to elevated temperatures. X-ray diffraction, thermal analysis (TGA and DTA) and scanning electron microscopy (SEM) were used to investigate the microstructural characteristics of the studied materials. The results showed that the presence of BFS in the geopolymer mixture significantly increases its mechanical response. However, the incorporation of SF presents inferior behavior in regular conditions and when exposed to elevated temperatures. The replacement of sand with chamotte results in higher compatibility above 500ºC, when a better tolerance to extreme environmental temperature conditions was observed.

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