Akademik Veri Yönetim Sistemi
4th International Symposium on Graduate Research, İzmir, Türkiye, 17 - 19 Aralık 2025, ss.17, (Özet Bildiri)
The construction industry is experiencing a significant transformation with the adoption of 3D printing technology, which allows the production of complex geometries without the need for traditional formwork. This development has shifted research attention toward the rheological properties of 3D printable concretes, as their flow behavior and buildability are key factors influencing print quality and structural performance. Accurate measurement of rheological parameters, such as yield stress, viscosity, and structural build-up, is therefore essential to ensure proper extrudability and stability of fresh mixtures. In this study, 3D printable Portland cement-based mixtures containing hydroxypropyl methylcellulose (HPMC) and a superplasticizer were prepared with a water-to-cement ratio of 0.30. Rheological properties were investigated using a vane probe system with two mixing protocols, M1 (single protocol for static yield stress and flow curve measurements) and M2 (separate protocols for these measurements), and two mixing protocol application procedures (P1 and P2) to observe time-dependent behavior at 15 and 30 minutes. In P1, the probe remains immersed throughout the resting period, whereas in P2 it is inserted immediately before testing. Static yield stress, dynamic yield stress, and plastic viscosity were determined, and the effects of probe immersion timing and mixing protocol application procedure on measurement results were assessed. The results show that the static yield stress values at 15 and 30 minutes were identical for both mixing protocols, as static measurements are taken before any shear disturbance and are therefore unaffected by the mixing protocol. The only notable difference occurred between the mixing protocol application procedures (P1 and P2), indicating that probe immersion timing is the main factor governing the accuracy of static yield stress measurements. Therefore, the P1 procedure is considered more reliable because the continuous probe–material contact captures the uninterrupted structural build-up, yielding consistently higher and more representative static yield stress values than P2. The dynamic yield stress and plastic viscosity values increased significantly between 15 and 30 minutes. Both parameters were strongly influenced by the mixing protocol and the mixing protocol application procedure, with the P1 procedure and the M2 protocol providing higher and more sensitive measurements at both ages. It was also observed that the vane probe created a cavity that did not fully close over time, highlighting the importance of testing undisturbed samples. This research underscores the significance of selecting appropriate measurement protocols for time-dependent rheological analysis in 3D printable concretes and contributes to establishing standardized procedures for characterizing fresh-state behavior, ultimately supporting the development of printable mixtures with improved buildability and structural performance.