Influence of the Size of Milled Coal Gangue Particles on the Mechanical Properties of Geopolymers

: Geopolymers are inorganic materials resulting from the synthesis of silicon and aluminum in a polycondensation reaction. In this study, coal mine waste material from the Wieczorek mine in the ´Sl ˛askie Voivodeship was used to produce geopolymers. The material was prepared, crushed and milled beforehand due to its large dimensions. The material was subjected to sieve analysis, which allowed to distinguish three fractions. The next step was thermal activation of the obtained powder grain sizes. After thermal activation, the material was combined with an alkaline solution to prepare geopolymers. Photographs of the microstructure were taken in order to determine the chemical composition of the geopolymer and to study the phase composition. The best compressive and bending strengths were exhibited by geopolymer samples with particle sizes ranging below 200 µ m—19 MPa and 5.7 MPa, respectively.