In recent years, there has been a growing interest in digital construction techniques such as 3D printing with concrete by layered extrusion. While this method offers various benefits, it also imposes high requirements regarding the rheological characteristics of printable materials. With the abandonment of traditional formwork, it becomes crucial for printable mortars and concretes to swiftly adapt their consistency to each stage of the process. Accordingly, material behavior can shift by several orders of magnitude within a short period of time, posing significant challenges for both mix design and test methodology to assess the rheological behavior of fresh concrete. Attention must especially be paid to the static parameters, and their evolution over time, as they are used to define the buildability of 3D printable materials. This research addresses the structural build-up of cementitious materials in their fresh state. One goal is to develop and refine a methodology that allows the characterization of a wide range of materials, as well as their modeling. The research focusses on high-potential test methods, with particular emphasis on rotational rheometry and penetration tests. The methodology developed is further utilized to explore the mechanisms behind the influence of aggregate properties and fiber addition on the rheological behavior and process-related parameters of fresh concrete in the context of 3D printing. The findings are utilized to propose models capable of predicting the material behavior during printing processes and preventing failure. Finally, this research facilitates a rheology-based approach to mix design.