Fonseca Mariana, Matos Ana Mafalda
Associação CECOLAB, Collaborative Laboratory Towards Circular Economy, 3405-155 Oliveira do Hospital, Portugal.
CONSTRUCT-Labest, Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal.
Materials (Basel). 2023 Mar 20;16(6):2458. doi: 10.3390/ma16062458.
Three-dimensional Cementitious materials Printing (3DCP) is a cutting-edge technology for the construction industry. Three-dimensional printed buildings have shown that a well-developed automated technology can foster valuable benefits, such as a freeform architectural design without formworks and reduced human intervention. However, scalability, commercialization and sustainability of the 3DPC technology remain critical issues. The current work presents the ecological fragility, challenges and opportunities inherent in decreasing the 3DCP environmental footprint at a material level (cementitious materials and aggregates). The very demanding performance of printable mixtures, namely in a fresh state, requires high dosages of cement and supplementary cementitious materials (SCM). Besides the heavy carbon footprint of cement production, the standard SCM availability might be an issue, especially in the longer term. One exciting option to decrease the embodied CO of 3DCP is, for example, to incorporate alternative and locally available SCM as partial cement replacements. Those alternative SCM can be wastes or by-products from industries or agriculture, with no added value. Moreover, the partial replacement of natural aggregate can also bring advantages for natural resource preservation. This work has highlighted the enormous potential of 3DCP to contribute to reducing the dependence on Portland cement and to manage the current colossal wastes and by-products with no added value, shifting to a Circular Economy. Though LCA analysis, mixture design revealed a critical parameter in the environmental impact of 3DCP elements or buildings. Even though cement significantly affects the LCA of 3DCP, it is crucial to achieving adequate fresh properties and rheology. From the literature survey, mixtures formulated with alternative SCM (wastes or by-products) are still restricted to rice husk ash, Municipal Solid Waste ashes and recycled powder from construction and demolition wastes. Natural aggregate replacement research has been focused on recycled fine sand, mine tailing, copper tailing, iron tailing, ornamental stone waste, recycled glass, crumb rubber, rubber powder and granules, recycled PET bottles and steel slag. However, flowability loss and mechanical strength decrease are still critical. Research efforts are needed to find low-carbon cement replacements and mix-design optimization, leading to a more sustainable and circular 3DCP while ensuring the final product performance.
三维水泥基材料打印（3DCP）是建筑业的一项前沿技术。三维打印建筑已表明，成熟的自动化技术能够带来诸多宝贵益处，比如实现无模板的自由形式建筑设计并减少人工干预。然而，3DPC技术的可扩展性、商业化和可持续性仍是关键问题。当前工作揭示了在材料层面（水泥基材料和骨料）降低3DCP环境足迹所固有的生态脆弱性、挑战和机遇。可打印混合物在新拌状态下对性能要求极高，这需要高剂量的水泥和辅助胶凝材料（SCM）。除了水泥生产的巨大碳足迹外，标准SCM的可用性可能是个问题，尤其是从长远来看。例如，减少3DCP内含碳量的一个令人兴奋的选择是掺入替代的且当地可得的SCM作为部分水泥替代品。这些替代SCM可以是工业或农业产生的废物或副产品，没有附加值。此外，部分替代天然骨料对自然资源保护也有好处。这项工作突出了3DCP在减少对波特兰水泥的依赖以及管理当前大量无附加值的废物和副产品方面的巨大潜力，从而转向循环经济。通过生命周期评估分析，混合料设计显示是3DCP构件或建筑环境影响的一个关键参数。尽管水泥对3DCP的生命周期评估有重大影响，但对于实现足够的新拌性能和流变学来说它至关重要。从文献调查来看，用替代SCM（废物或副产品）配制的混合物仍局限于稻壳灰、城市固体废弃物灰以及建筑和拆除废物回收粉末。天然骨料替代研究主要集中在再生细砂、尾矿、铜尾矿、铁尾矿、观赏石废料、再生玻璃、碎橡胶、橡胶粉和颗粒、再生PET瓶以及钢渣。然而，流动性损失和机械强度降低仍然是关键问题。需要开展研究工作来寻找低碳水泥替代品并优化混合料设计，在确保最终产品性能的同时实现更可持续和循环的3DCP。
