Enhancing Interlayer Bond Strength of 3D-Printed Concrete Through Microstructural Densification by Means of Incorporating Sugarcane Bagasse Ash (2026-02)¶

3D-Printed Concrete (3DPC) is fabricated layer by layer, generating interlayer regions that typically exhibit elevated porosity and discontinuities. These interlayer interfaces act as mechanical weak links that govern failure initiation and load transfer across printed filaments, making interlayer bond strength a primary performance limiter. This study investigates a sustainable route to strengthen interlayer adhesion while reducing interface porosity by partially replacing cement with sugarcane bagasse ash (SBA). A comprehensive experimental program combined tensile and pull-off testing with microstructural characterization by scanning electron microscopy (SEM), X-ray diffraction (XRD), and micro-computed tomography (µ-CT). Five series of mixtures were produced with SBA contents increasing from 0 % to 20 % in 5 % increments. The mix with 15 % SBA delivered the best overall performance, with tensile strength and bond strength increases of 10.0 % and 31.4 %, respectively, after 90 days of curing. SEM revealed a refined interface microstructure; XRD indicated increased calcite formation in SBA-modified specimens. µ-CT results showed a 69 % reduction in porosity for the 15 % SBA mix compared with the control at 90 days, together with a more compact pore network. These findings demonstrate that SBA is an effective partial cement replacement for densifying interface regions and improving interlayer adhesion, thereby advancing sustainable practices in 3D concrete printing.