Performance optimization of polymer-modified 3D-printed colored composites

• Experiments were designed using a Taguchi L 9 matrix with four factors and three levels. • The Taguchi method was applied to optimize the performance of 3D printed composite containing polypropylene fiber (PPF), styrene-butadiene rubber (SBR), and red-colored iron oxide pigment (IOP) • The composites were manufactured through mold casting and 3D printing methods • Mechanical and durability properties were systematically evaluated. • 3D-printed composites exhibited lower performance than the mold-cast counterparts. Three-dimensional (3D) printing of cementitious materials allows for tailored and aesthetic designs; however, adding polymers, fibers, and pigments can compromise printability, mechanical performance, durability, and aesthetics. This study investigates the development of 3D printed polymer-modified colored concrete for construction applications. Four variables were examined, including water-to-binder ratio (w/b), polypropylene fiber (PPF), styrene-butadiene rubber (SBR), and red-colored iron oxide pigment (IOP), to determine the optimized fresh and hardened properties. The metakaolin-based mixtures were designed using the Taguchi method with four factors at three levels, forming an L 9 orthogonal array. Performance criteria included flowability, compressive and flexural strength, interlayer bond strength, ultrasonic pulse velocity, colorimetry, water absorption, and carbonation resistance. Test results revealed that the compressive strength reduced with SBR and PPF additions, albeit this was mitigated by decreasing the w/b. SBR notably enhanced flexural and bond strengths but negatively affected durability owing to increased porosity that contributed to water and CO₂ ingress. Statistical analysis confirmed that the w/b ratio was the dominant factor influencing most performance criteria, while IOP had a comparatively minor effect on mechanical and durability-related properties. The optimal mixture consisted of a 0.35 w/b ratio, 0.5% PPF, 4% SBR, and 1% IOP. The study demonstrates an effective approach for designing 3D printable colored concrete with balanced mechanical performance, durability, and aesthetics.