3D printed alkali activated materials for reduced anisotropy and concrete repair applications
Construction and Building Materials, cilt.540, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 540
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.conbuildmat.2026.147582
- Dergi Adı: Construction and Building Materials
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, INSPEC
- Anahtar Kelimeler: Alkali-activated material, And Interface bond, Anisotropy, Concrete repair, Printing path, Three-dimensional (3D) printing
- Ankara Üniversitesi Adresli: Evet
Özet
The application of 3D concrete printing (3DCP) for structural repair is an emerging technology. While slant surface repairs are common, the bond performance of the 3D- printed repair material-slant substrate interface has not been well understood. This study investigates the fresh-state properties, mechanical anisotropy, and slant surface repair performance of a 3D-printed alkali-activated material (3DPAAM). This mixture was made of fly ash (FA) and ground granulated blast-furnace slag (GGBFS) activated with NaOH solution. It was printed with three deposition paths (0°, 45°, and alternating 45°+135° printing directions). The fresh-state properties evaluated included setting time, flowability, extrudability, open time, and buildability. The compressive, flexural, and bond strengths of printed samples under various loading directions were tested, and the influences of printing paths on mechanical anisotropy were assessed. The 3DPAAM mixture was also used to repair substrates with slant angles ranging from 0° to 60°. The performance of the printed repair material-substrate bonds was evaluated using slant shear and splitting tensile strength, ultrasonic pulse velocity (UPV), and scanning electron microscopy (SEM). The results indicate that fresh-state properties of the 3DPAAM (extrudability of 93.5 ± 0.2%, open time of 50 min, and buildability of 97 ± 0.3%) were suitable for 3DCP. Compressive strength of the 3DPAAM reached 24–36 MPa at 28 days and 29–39 MPa at 56 days, while flexural strength ranged from 6.1 to 9.7 MPa at 28 days, depending on the printing and loading directions. Compared with the 0° printing path, 45° and 45° + 135° paths reduced mechanical anisotropy. Increasing substrate inclination resulted in a gradual reduction in the repair material-substrate bond quality, with splitting tensile bond strength decreasing from 1.61 to 1.43 MPa, accompanied by increased UPV delay and interfacial degradation observed by SEM. These results demonstrate that optimized printing strategies can reduce anisotropic behavior and 3DPAAM has a high potential for repairing slant concrete surfaces, supporting the development of reliable and automated 3D concrete repair technologies for complex infrastructure.