Permeability and electrical resistivity of 3D-printed mortars using local materials (zeolite, calcined clay, and mussel shell powder), Aotearoa – New Zealand

3D concrete printing (3DCP) is an innovative technique that promises to enhance the global construction industry. However, due to the absence of large aggregates in printable mixes, most of the mixes for 3DCP in the literature contain a significant component ( ∼ 480 kg/m 3 ) of Portland cement, which contributes to large embodied carbon emissions. In response to the limited supply of traditional supplementary cementitious materials (SCMs) (e.g., fly ash and ground granulated blast-furnace slag) in Aotearoa - New Zealand, it is necessary to explore alternative local materials. The durability properties, which are crucial for the long-term performance and sustainability of structures, remain underexplored in 3DCP. This study analyses the permeability and electrical resistivity of novel 3D concrete printing mixes developed using locally-sourced zeolite and calcined clay, and recycled mussel shell powder materials as SCMs. Printed and cast specimens were subjected to oxygen permeability, electrical resistivity, and porosity tests at 7, 28, and 90 days. Results showed that zeolite can be used in printable mixes for 3DCP, especially in binary blends with up to 40 % cement substitution. Z40 printed samples were the only specimens with an electrical resistivity greater than 1340 Ω ∙ m from 28 days onwards, which indicates negligible chloride ion penetration. On the other hand, the use of local clay negatively influenced the porosity levels and electrical resistivity of samples, compared to the benchmark and the zeolite-based binders. The use of mussel shell powder, as a source of calcium carbonate, is not feasible in the proportion used in this study, and further research is required. • Durability properties of cast and printed mortar specimens are assessed. • Effects of alternative Supplementary Cementitious Materials (SCMs) on durability. • Challenges regarding levels of cement substitution by using the alternative SCMs. • Recommendations for future research are presented.