Printability Assessment of 3D Printing Cement–Lime Mortars with Microencapsulated PCM

An experimental study was conducted to evaluate the printability of cement–lime mortars designed for 3D printing applications, incorporating a microencapsulated phase-change material (PCM) and cellulose microfibers (CMFs). The influence of both PCM and CMFs on mortars’ rheology was measured by rheometer tests (DSR) and cone penetration tests (CPT). A ram extrusion test was used to evaluate the extrudability, and an unconfined uniaxial compression test (UUCT) allowed the assessment of buildability. Finally, several lab-scale prototypes were 3D-printed. The results showed that the incorporation of PCM affected mortar’s rheology and workability due to the reduction in paste volume and the increase in superplasticizer (SP) demand. However, the spherical particle shape of microencapsulated PCM was found to ease the extrusion process. After being extruded, mortars with lower volumetric fractions of PCM exhibited increased fresh strength and stiffness, whereas larger amounts reduced both parameters. The use of CMFs considerably reduced the extrusion force and improved the extrusion quality. Lab-scale 3D-printed prototypes were successfully manufactured using mortars with a 20% volumetric fraction of PCM.