<![CDATA[This study aimed to optimize the composition of interlocking bricks made from local Andosol soil and fly ash to achieve the highest compressive strength within the investigated composition ranges while limiting cement content. A Taguchi L27 orthogonal array was used to investigate three factors: fly ash (0%, 8%, and 16%), cement (6%, 8%, and 10%), and sand (0%, 2%, and 4%). Andosol soil constituted at least 70% of the mixture. The 27 treatment combinations, each with three replications, produced 81 specimens tested at 28 days. Compressive strength ranged from 0.40 to 2.00 MPa, with an overall mean of 0.78 MPa. Response analysis, signal-to-noise (S/N) ratio analysis, analysis of variance (ANOVA), and factor interaction analysis identified cement as the most influential factor, contributing 29.04%. The final composition differed from the main-effect candidate because factor interactions were also considered. The selected composition comprised 80% Andosol soil, 8% fly ash, 10% cement, and 2% sand. The predicted compressive strength was 1.62 MPa, while the confirmation experiment yielded an average of 1.77 MPa, with a relative error of 8.74%. These results demonstrate the applicability of the Taguchi method for optimizing the compressive strength of Andosol-based interlocking bricks.]]>
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