Effect of Sisal Fibers on the Behavior of 3D-Printed Cementitious Mixtures Exposed to High Temperatures (2025-08)¶

When exposed to high temperatures, 3D-printed cementitious composites (3DP-CC) often exhibit delamination and poor interlayer bonding. This study aims to develop a 3D-printable cementitious composite reinforced with sisal fibers (3DP-SFCC) and to experimentally evaluate the impact of elevated temperatures on the mechanical, physical, and microstructural behavior of both printed and cast specimens. The 3DP-SFCC mixtures were developed with appropriate buildability for extrusion-based printing systems, incorporating sisal fibers of 6 mm and 12 mm in length at volumetric contents of 0.5 % and 1.0 %. The mixes also included limestone filler and metakaolin. Extrudability, rheological properties, and green strength were evaluated, and physical, mechanical, and microstructural properties were assessed before and after exposure to 200, 400, 600, and 800 °C. Incorporating sisal fibers improved green strength but reduced the mechanical performance of unheated 3DP-SFCC in the hardened state. However, at high temperatures, tests demonstrated that sisal fibers prevented interlayer adhesion loss up to 400 °C, while fiber-free mixtures showed a ∼37 % reduction in interlayer adhesion at the same temperature. Sisal fibers mitigated compressive strength losses at all temperatures analyzed, reducing the strength loss from 34 % in REF-C to only 0.3 % in SF05%12 at 600 °C in the Y direction. Damage was mitigated, especially with the use of 12 mm fibers, and the impact of heating on the anisotropy induced by the 3D printing process was reduced, reinforcing that 3DP-SFCC exhibits improved performance in environments prone to elevated temperatures.