Abstract: Lignite fly ash from the Kosovo B thermal power plant is a major industrial by-product that can be used as a supplementary cementitious material (SCM). Through a comprehensive two-year monitoring program in 2024 and 2025, this paper presents a study of lignite fly ash from the Kosovo B thermal power plant. The study showcases and monitors its chemical traits, mechanical performance and industrial viability. This study, through the use of X-ray fluorescence (XRF) analysis, found that fly ash contains an average of 32.28% $$\mathrm{SiO_2}$$, 9.01% $$\mathrm{Al_2O_3}$$, 6.76% $$\mathrm{Fe_2O_3}$$, and 32.93% $$\mathrm{CaO}$$, with a loss on ignition (LOI) of 2.88%. These characteristics are comparable to Class C fly ash according to the classifications of ASTM C618 and EN 450-1. Regarding average compressive strengths, they reached 14.66 MPa at 7 days and 35.14 MPa at 28 days. Statistical analysis revealed variations over the two years; notably, moisture content negatively impacted early strength $$(r = -0.547)$$, while $$\mathrm{MgO}$$ exhibited a moderate negative correlation with 28-day strength $$(r = -0.411)$$. These results are consistent with high-calcium fly ashes reported in international studies. The benefits of greater use of this material include a reduction in clinker demand, conservation of raw materials, and support for the reuse of industrial by-products in cement production.

Keywords: Fly ash, Supplementary cementitious material, Compressive strength, XRF analysis, clinker replacement, Sustainability

Pages: 1184-1190