Rheological and 3D printing assessment of sisal fiber mortar for architectural applications

3D printing mortars are becoming a focus of interest for architectural appli-cations, due to their ability to produce free shaping designs. However, there are still some printability and performance issues that require further research, as the incorporation of reinforcing and the improvement of sustainabil-ity by reducing its carbon footprint. Natural fibers become an excellent alterna-tive to overcome these problems, enhancing mortar performance. The aim of this study was to evaluate rheology and printability of mortars with sisal fibers (SF) for architectural 3D printing applications. A reference cement mortar with 0-0.6 mm sand and 0.45 water to cement ratio was designed. Then, 13 mm length SF in volumetric fractions (VF) of 0.5, 1 and 1.5%, and 6.5 mm length SF at 1%VF were added. Four tests were carried out to evaluate fresh rheologi-cal and mechanical properties of mortars: flow table test, self-weight cone-penetration test, displacement-controlled cone-penetration test and uniaxial fresh compression test. Mortar printability was evaluated with a manual extrud-er and a 3D robotic printer, reaching an open time window of 90 minutes. It was observed that 3D printing produced an alignment of SF. Larger SF amount gradually increased initial yield stress and structural build up. The VF and length of SF maintained initial compressive yield stress, enhancing tenacity of fresh material. Mortars with low VF of SF showed good printability, although higher SF VF produced some printing issues due to their lower pumpability.