Evaluation of different fly ash samples on the production of alkali-activated materials

Avaliação de diferentes amostras de cinza volante na produção de materiais álcali-ativados

abstract:

In this work, different samples of fly ash (FA-A and FA-B) classified as type F as used to produce the AAM samples. The FA-A presented a higher Fe₂O₃ content than FA-B, 6.1 to 3.8 wt.%, and a slightly higher SiO₂/Al₂O₃ ratio of 3.52 in comparison to 3.34 of FA-B. The average particle size (D50) of fly ash A was 19.7 µm and of fly ash B 30.8 µm, while the specific mass of the ashes A and B were 2.38 and 2.21 g/cm³, respectively. The results revealed that the mechanical strength of the AAM produced with fly ash A was higher than fly ash B, close to 80 and 44 MPa, respectively. The variation of the strength has been attributed to the different SiO₂/Al₂O₃ ratios and different particle sizes. The mechanical strength decreased with increasing curing time, which is attributed to excess alkali in the system. Only very small differences in porosity and density have been found.

Keywords:
alkali-activated materials; fly ash; alkali activation; mechanical strength