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Underwater three-dimensional (3D) concrete printing has a great potential to be applied in submarine construction, but there tends to be significant dispersion and strength reduction of the printed concrete due to washout by surrounding water. This research tried to overcome such problems by enhancing the washout resistance and strength of the printable concrete. A series of seawater coral sand mortar mixes containing silica fume (SF), nano silica (NS), glass fibers (GF) and/or hydroxypropyl methyl cellulose (HPMC) were produced, printed under seawater, and tested for their underwater printability and mechanical properties. The test results showed that both SF and NS can enhance the washout resistance, extrudability and buildability, and improve the flexural, compressive, and bond strengths. GF has also positive but relatively smaller effects. On the other hand, HPMC can improve the underwater printability and bond strength, but may have adverse effects on the flexural and compressive strengths. GF and HPMC, when added together, could cause difficulties in underwater printing, and thus are incompatible. Nevertheless, the combined addition of SF, NS, and HPMC greatly enhances the underwater printability and mechanical properties. Based on these results, some anti-washout 3D printable mortars for submarine construction were developed.
Li et al. (Mon,) studied this question.
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