Optimizing multi-component cementitious composites requires a comprehensive understanding of not only the isolated effects of individual components but also their complex, often non-linear, inter-factor interactions. This study aims to perform mathematical modelling and evaluate the combined effect of the cement-to-fly ash ratio, fibre content, and plasticizer dosage on the compressive strength of the composite to identify optimal technological parameters. Experimental data were analyzed using one-way and multi-way analysis of variance (ANOVA). Two-factor quadratic regression equations and 3D response surface plots were generated utilizing the STATISTICA software suite. A strong synergistic effect was detected within the “Cement × Fibre” interaction system (xy = +0.0557). The findings demonstrate that micro-reinforcing fibres effectively enhance compressive strength only when embedded in a high-density matrix (cement-to-fly ash ratio ≥ 1.00). The interaction between the fibre and plasticizer factors exhibited a saddle-shaped response surface, indicating a drop in compressive strength below 31 MPa if the rheological balance of the mixture is disrupted. The absolute experimental maximum was identified, yielding a compressive strength exceeding 52 MPa. The derived regression models enable flexible control over the composite formulation, allowing for variations in additive dosages without sacrificing load-bearing capacity, or the targeted synthesis of materials with enhanced mechanical performance.
