CHEMOACTIVATION OF EKIBASTUZ FLY ASH IN CEMENT

Abstract

The scientific article comprehensively examines the issue of the effective use of fly ash–a major tonnage of technogenic waste from the Ekibastuz GRES-in construction materials, specifically in cement compositions and hyper-pressed products. The main scientific novelty and primary objective of the study is to increase the low hydraulic activity of high-silica (acidic) fly ash through chemoactivation with a sodium hydroxide (NaOH) solution, and its effect on the physicomechanical properties of hyper-pressed brick is scientifically substantiated. During the experimental studies, 2%, 4%, and 6% concentrated sodium hydroxide (NaOH) solutions were used to activate the fly ash. The research results showed that as the concentration of the alkaline reagent increased, the dissolution of the amorphous phase on the surface of the ash particles accelerated, leading to more intensive hydration processes of the cement matrix. In particular, The use of chemically activated ash at a 4% NaOH concentration significantly increased the density of the cement composite and improved the early and design (28-day) strength values by 15-20% compared to the control samples. In addition, the article presents the results of X-ray phase and electron microscopic analyses of the microstructure of hyper-pressed brick. These analyses demonstrate that chemical activation of ash leads to the formation of additional calcium hydro-silicates, reduces the material's porosity, and strengthens its structure. The practical significance of the work is directed at increasing the level of waste utilization in the construction industry, saving on cement consumption, and improving the technology for obtaining environmentally safe, high-strength hyper-pressurized products. The obtained results make it possible to improve the ecological situation in the Ekibastuz region and reduce the cost of construction materials.