Akademik Veri Yönetim Sistemi
4th International Symposium on Graduate Research, İzmir, Türkiye, 17 - 19 Aralık 2025, ss.18, (Özet Bildiri)
The usage of supplementary cementitious materials (SCMs) as partial replacements of ordinary Portland cement (OPC) is, to date, the most plausible and conventional way to bring sustainability and environmental friendliness into 3D printable concrete (3DPC) technology, which inherently requires a higher binder volume to achieve the performance requirements of printable mixes. Additionally, the combination of a lower aggregate-to-binder ratio, the absence of coarse aggregate, and the lack of formwork during printing makes 3DPC more susceptible to shrinkage. Furthermore, the incorporation of microfibers as reinforcement is one of the ways to reinforce printed objects while maintaining the architectural freedom of 3DPC. Hence, in this study, the effect of pozzolans as SCMs for CEM I 42.5 R OPC on long-term autogenous shrinkage of fiber-reinforced printable mixtures was investigated. Accordingly, ground granulated blast furnace slag (BFS) and class F fly ash (FA) were used as partial substitutes for OPC at various ratios (0, 20, and 40 %) by weight. Additionally, micro steel fibers with a length of 6 mm were added to the mixes at 0.5% by volume. The long-term autogenous shrinkage strains of the printable mixtures were determined on specimens sealed with aluminum adhesive tape, in accordance with ASTM C-157 standard. The sealed specimens were conserved for 56 days at 20 oC and 95% RH in a climate chamber. Also, the 7- and 28-day compressive strengths were determined on mold-cast samples after standard water curing. Results show that the long-term shrinkage behavior of the studied mixes varied in accordance with the type of pozzolans, their replacement ratio, and the maturity of the mixture. The addition of BFS resulted in higher overall shrinkage strains of all mixtures, especially on the 56th day. The addition of 20% and 40% BFS increased the shrinkage strains at the 56th day by 13% and 11% respectively. Additionally, the addition of BFS at 20% resulted in higher shrinkage than the 40% addition during the first three days. Unlike BFS, results indicate that the incorporation of FA mitigated the shrinkage behavior of the studied mixes. FA-bearing mixes showed the lowest shrinkage strains of all mixtures at the 56th day. The addition of FA at 40% reduced the overall shrinkage strains by 38% and 56.6% in comparison to the reference and the mixture with 40% BFS addition, respectively. While the effect of BFS on the 7 and 28-day compressive strength was negligible, 20 and 40% FA addition decreased the strength by 20% and 51% at 28 days compared to the reference mix.