Fracture and transport analysis of heterogeneous 3D-Printed lamellar cementitious materials

This paper investigates the spatial characteristics of microstructural phases in relation to the fracture toughness in Mode-I/II and transport behavior in two orthogonal directions of lamellar 3D-printed cement paste compared to cast counterparts. Using segmentation techniques, it was found that intact 3D-printed materials represent porous interfaces and microchannels. A modified partial-notch Brazil-Nut test was proposed to characterize the Mode-I/II fracture toughness. A new laser-notching process was proposed to generate a sharp notch and account for the sensitivity of fracture processes to microstructural heterogeneities in 3D-printed materials. Unlike Mode-I, significantly higher Mode-II fracture toughness was found in 3D-printed material in the perpendicular direction compared to the cast, owing to the in/out-of-plane crack deflection along the interfaces. The porous interfacial regions were hypothesized to govern the crack initiation in both Mode-I/II. Water transport was characterized by absorption using Neutron Radiography, where interfacial heterogeneities act as capillary breaks, hence directionally influences water absorption and transport.