Optimization study and material properties of angular artificial aggregates

Natural aggregate exploitation and landfills of industrial and agricultural by-products in the environment are leading to serious environmental hazards. The practice of assigning economic value to by-products by utilizing them in the production of artificial aggregates has expedited significant research efforts. This study aimed to utilize Taguchi-integrated grey relational analysis to optimize the multivariable parameters of geopolymerization, thereby achieving the desired properties of artificial aggregates. Fly ash, paper sludge ash, and palm oil fuel ash were treated with alkaline solutions such as sodium hydroxide and sodium silicate according to the considered Taguchi design matrix. The product was crushed in a jaw crusher to produce angular artificial aggregates, a reliable method for industrial mass production. The physical properties, such as water absorption, aggregate impact value, and compressive strength tests, were analyzed and considered crucial optimization response indices. In addition, the XRF, XRD, and SEM of the precursors and artificial aggregates were investigated. Experimental results showed that the specific gravity and apparent density of produced aggregates were between 1.5 and 1.9 and 1400 to 1504 kg/m³, respectively. The microstructure inferred the presence of porous and rough surface texture. The study found the lowest water absorption of 18.7%, the lowest aggregate impact value of 26.2%, and the highest compressive strength of 36.6 MPa, which were achieved for a mix made of sodium hydroxide solution of molarity 12, alkaline solution ratio of 1.5, and raw materials proportions of 60:30:10. The findings in this study are helpful for their applications in concrete production.