Multi-level Characterization of a 3D Printing Cementitious Composite

This study characterizes a commercially available cement‑based composite formulated for extrusion‑based 3D printing. Although the exact formulation and supplier are confidential, the material consists of CEM I 52.5, fine quartz sand, limestone filler, rheological additives, and polypropylene fibers, with a water‑to‑solids mass ratio of 0.16. For comparison purposes, specimens were also produced by conventional casting using the same material and mixing conditions, allowing the influence of the manufacturing process to be evaluated. 3D‑printed specimens were produced with different geometries and printing parameters, including layer height and deposition strategy. Compressive strength was evaluated on cast specimens and on cylindrical cores extracted from printed elements. Hygrothermal behaviour was assessed by measuring thermal conductivity and capillary water absorption. The compressive strength of cast specimens increased from 45.9 MPa at 2 days to 61.5 MPa at 28 days, while compressive strength values between 55 and 80 MPa were obtained for cores taken from printed specimens. Printed specimens exhibited lower thermal conductivity (2.07 W/(m·K)) and lower capillary water absorption coefficients (0.00065 kg/(m2·s1/2)) than cast specimens (2.26 W/(m·K) and 0.00110 kg/(m2·s1/2), respectively). Microstructural analysis revealed the presence of elongated pores at interlayer regions in the printed material. These results indicate that, while compressive strength remains comparable, the manufacturing process affects the hygrothermal behaviour through changes in microstructure. Graphical Abstract