Multi-response Optimization of Quaternary Blended Mortar Using Taguchi–Grey Relational Analysis

This study aimed to reduce cement usage and promote effective utilization of industrial by-products by developing a quaternary mortar mix design using Taguchi–grey relational analysis (GRA). Municipal solid waste incineration fly ash (MSWIFA), ground granulated blast furnace slag (GGBFS), and fly ash (FA) were used as supplementary cementitious materials, and their optimal replacement ratios were proposed in the mix design. The optimal levels were analyzed in terms of the flowability, compressive strength, and cost analysis. The number of experiments and mix combinations was reduced by approximately 33% using the L9 orthogonal array. The S/N ratios obtained from the measurements, along with ANOVA, enabled the evaluation of the contribution of each parameter to individual responses. Based on the Taguchi–GRA method, the optimal mix design was determined to be 2.5% MSWIFA, 20% GGBFS, and 20% FA, which yielded the most favorable balance of flowability, compressive strength, and cost analysis. This result was verified through confirmatory experiments. The experimental validation supports the effectiveness and validity of the Taguchi–GRA-based mix design approach for optimizing quaternary mortar compositions.