Pozzolanic activity of low-quality clays by Frattini test

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Martina Šídlová, Rostislav Šulc, Tomáš Doležal, Karolína Králová, Martina Kohoutková, Klára Pulcová, Petr Formáček

Cement is one of the most used material in the world, including the Czech Republic. Its role in the construction industry is irreplaceable, but its production contributes to 5-8% of global CO2 emissions. One of the possibilities to reduce the amount of emissions is the production of blended cements that contain pozzolans, such as fly ash, slag, microsilica and, recently, the increasingly discussed calcined clays. The work was focused on the characterization and study of the pozzolanic activity of “low-quality” overburden clays from the Bílina lignite mine in the Czech Republic. A very variable composition of clays was found from the point of view of XRD analysis, while the amount of kaolinite in the 9 investigated samples was in the range of 5-20 wt.% and the amorphous phase was in the range of 23-63 wt.%. By calcination the clays at a temperature of 850°C, it was found that all calcined clays reliably exhibit pozzolanic properties using the Frattini test. By lowering the firing temperature to 650°C, the pozzolanic activity of some samples decreased significantly.

Keywords: Pozzolan activity; overburden clays; calcined clays; Frattini test

Proscience vol. 9

Pp 51-56

DOI: 10.14644/EC2023.009