International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

This study investigates the chemical, mineralogical, and functional characteristics of fermented grape pomace ash generated after brandy production and subsequent combustion. Semi-quantitative WDXRF analysis revealed a Ca–K–P-dominated composition with high alkalinity, significant phosphorus content, and notable copper concentration. The water-soluble fraction of the ash was determined to be 17.1 wt.%, indicating a moderate content of mobile inorganic salts that may influence leaching behaviour and environmental compatibility. XRD and vibrational spectroscopy confirmed the presence of lime, calcite, silicates, sulphates, and calcium phosphate phases, including hydroxyapatite, together with a significant amorphous fraction and residual carbon. UV–Vis analysis indicated partial reduction of copper species to metallic nanoparticles, suggesting heterogeneous redox conditions during thermal treatment. The combined composition confers potential functionality in soil amendment, mineral carbonation for CO₂ sequestration, and incorporation into cementitious or alkali-activated systems, although soluble salts and copper mobility represent critical constraints, requiring application-specific environmental and performance assessment.

The lightweight cellular building materials has driven significant interest recently due to increasing requirements of energy efficiency of the buildings. This study investigates the potential of fayalite slag, a by-product of copper production, as a precursor for lightweight geopolymer foams. Geopolymer foams were synthesized using a combination of fayalite slag and metakaolin, employing gas forming agents to achieve a porous cellular macrostructure. The influence of alkali concentration was examined on the cellular structure, physical properties and microstructure (FT-IR) of the resulting materials. The findings contribute to the development of sustainable, highperformance geopolymer materials suitable for insulation and fire-resistant applications.

Geopolymers based on natural zeolite clinoptilolite and addition of up to 50% metakaolin were synthesized using binary sodium/potassium alkali activator. The influence of metakaolin addition was evaluated on apparent density, water absorption, relative mass loss after watering and microstructure (XRD) of the prepared geopolymers. The addition of metakaolin greatly influenced the physical and mechanical properties of the obtained geopolymers. Minimal/optimal metakaolin addition was estimated to 30% in the respect of sufficient strength (11 MPa) and the high price of metakaolin. The resulted geopolymer based on natural zeolite and metakaolin (30%) contained residual unreacted clinoptilolite which could be beneficial for properties of future geopolymer products. Potential applications of obtained geopolymer-clinoptilolite agglomerates are: waste or radioactive water decontamination, passive cooling systems, plasters in residential buildings, etc.

Geopolymer based on iron-silicate fines (fayalite slag) were synthesized in alkaline and acidic media using activation solution
comprised of respectively alkali silicate and phosphoric acid solutions. The raw material consists of fayalite, magnetite and pyroxene which could be a conglomerate in some particles. The alkali activation occurs very slow at room temperature, while acid activation take place very rapid. The acid activated geopolymer binder phase include cracks probably formed by thermal gradient because of the rapid exothermal reaction. The morphology of the alkali activated geopolymers were presented by porous structure.