Utilization of phlogopite as alkali activated material

Abstract

This bachelor’s thesis explores the potential of using phlogopite residue and side streams for alkali activation, aiming to contribute to the circular economy and provide a sustainable alternative to traditional cement. The study investigates the effects of sonication on the alkali activation process and the resulting material strength.

Alkali activation of phlogopite and blast furnace slag (BFS) was performed using two different concentrations of NaOH (2 M and 6 M), with particular attention to the performance of samples without addition of sodium silicate. The results demonstrated that the sample with 23 wt.% of phlogopite achieved the highest strength across all curing times, comparing 2 M samples. Notably, it showed a sixfold increase in strength on the 3rd day. This significant strength development was achieved when sodium silicate was added to the alkali activated mixture before casting.

Further analysis of samples using 6 M NaOH without adding sodium silicate revealed that the sample without phlogopite, BFS100, had the lowest strength but showed steady improvement over time. Comparisons between blank and sonicated samples indicated that while initial strengths were similar, differences became more pronounced over longer curing periods, with non-blank sample of 23 wt.% phlogopite consistently outperforming others. The similar compressive strength of this sample and 23 wt.% phlogopite (2 M) samples highlight the potential for simpler and more cost-effective formulation where no sodium silicate is added.

The study underscores the importance of optimizing alkali concentration and curing time to enhance the strength of alkali-activated materials that contain phlogopite. The findings suggest that sonication can effectively improve the activation process, leading to higher strength outcomes. Overall, this research supports the viability of using aluminosilicate mining wastes as a sustainable and high-performance alternative to traditional cement, contributing to the advancement of circular economy practices.