Optimization of alkali-activated ladle slag-fly ash composites using a Taguchi-TOPSIS hybrid algorithm

The effect of multiple mix design factors on the properties of ladle slag-fly ash alkali-activated composites was investigated. Taguchi-TOPSIS hybrid algorithm was adopted to optimize mix design parameters, including ladle slag replacement by fly ash (LSR), sodium hydroxide molarity (SHM), the ratio of sodium silicate to sodium hydroxide (NS/NH), the ratio of alkaline activator solution to binder (AAS/B), and crushed stone replacement by desert dune sand (CSR). The results revealed that the mix proportions of the optimum strength response comprised LSR, AAS/B, SHM, NS/NH, and CSR of 10%, 0.5, 8 M, 2, and 75%, respectively, with a compressive strength of 21 MPa. Conversely, the mixture proportions for superior fresh properties had a flow of 240 mm and entailed LSR, AAS/B, SHM, NS/NH, and CSR of 40%, 0.5, 8 M, 2.5, and 75%, respectively. Additionally, the hybrid method prediction model proved to be robust, with the ability to predict strength and workability at 93 and 100% accuracy. The optimum mixes comprised an intermix of calcium aluminosilicate hydrate and sodium aluminosilicate hydrate gels, with traces of calcium silicate hydrate gel, as identified by microstructure analysis and using ternary diagram system of Ca/Si-Na/Si-Al/Si ratios.