A group of international researchers has produced binder jet 3D printed geopolymer structures competitive with structural concrete for various applications.
The primary goal of the research was to 3D print metakaolin, a dehydroxylated form of the clay mineral kaolinite, without the use of cement.
通过创建一个原料由沙子和完全的metakaolin, the team was able to produce prism-shaped geopolymer components with defect-free powder layers in what they claim is a cleaner and more sustainable production process.
Benefits of geopolymers
3D printing has been increasingly used within the construction sector in recent years, however cement manufacturing has long been associated with higher greenhouse gas emissions and energy consumption, which deteriorates the overall sustainability of 3D printed concrete structures. Cement is also subject to high autogenous shrinkage, heat of hydration, and high costs.
By comparison, geopolymers offer a fast-setting, cost-effective and eco-friendly alternative, providing enhanced fire resistance and durability compared to conventional cement composites. As such, research into 3D printing geopolymer structures able to rival conventional materials like structural concrete has garnered more attention in recent years.
Back in 2017, for instance,NTU Singaporecreated ageopolymer cement using waste fly ash particlesproduced as a by-product of the coal combustion process. The use of fly ash significantly reduced the carbon footprint of the traditional cement production process while also delivering superior heat-resistant properties to the material.
More recently in 2020, the斯威本技术大学and French construction firmBouygues Travaux Publics部署的机器学习技术来开发较强的3D印刷地球聚合物水泥and a subsequent roadmap for classifying the stability of other 3D printed compounds used in the construction sector.
3D粘合剂喷射地球聚合物
该领域的最新研究来自一支来自Stone 3D印刷公司的国际研究人员团队Desamaneraand theUniversity of Padovain Italy, Egypt’s国家研究中心,Pennsylvania State University在美国，Ceramic and Mineral Resources Technology Center(CETMIC) in Argentina.
该研究的主要目的是在不使用水泥的情况下打印Metakaolin。为了实现这一目标，研究人员开发了一种肉芽技术，使他们能够生产具有“合理”流动性的原料，该原料由Metakaolin覆盖的沙颗粒组成。
活页夹3D打印过程使研究人员能够利用梅塔科林与碱性溶液反应时发生的地质聚合过程。
通过将碱性溶液喷射到粉末床上，肉芽过程使粉末床中的Metakaolin（30 wt％）的比例更高，并确保印刷无缺陷的粉末层。在印刷过程中，喷射的碱性溶液与颗粒中存在的Metakaolin粉末反应，形成地质聚合物。
该小组选择了一个大规模的市售粘合剂喷气机3D打印机来生产由两个原料组成的结构地球聚合物组件。一种完全由梅塔毛林和沙子制成，另一个由粉末混合物中的少量商业快速设置水泥制成。
During the study, all of the 3D printed samples were found to be water-resistant, with no significant differences in strength after seven days of exposure to water. The 3D printed geopolymer parts fabricated with 30 wt% metakaolin exhibited a compressive strength of 20 MPa, even with a 30% volume of residual porosity.
The researchers observed the 3D printed geopolymers containing only metakaolin possessed the same printing accuracy and resolution as those containing cement. According to the team, this confirmed the high reactivity of the corresponding metakaolin granules to prepare the geopolymer gel for fabricating strong, high-resolution geopolymer parts without the need for cement.
该团队的颗粒技术使得将较高的细胞和反应性metakaolin颗粒的较高含量引入粉末床中，以维持原料的流动性并允许打印无缺陷层。
The team also found that adding rapid-setting cement to the powder bed had no effect on the printing accuracy or strength of the geopolymer parts. With no significant changes in strength observed after submerging the 3D printed geopolymer structures in water for a week, the team believes its formulation could be used in outdoor and water-interacting applications.
Further information on the study can be found in the paper titled:“雷电竞充值使用地球聚合物和粘合剂喷射的无机组件的添加剂制造”发表在《添加剂制造杂志》上。雷电竞充值该研究由H. Elsayed，F。Gobbin，M。Picicco，A。Italiano和P. Colombo共同撰写。
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Featured image showsformation and binder jet 3D printing process for the metakaolin and sand feedstock. Image via Additive Manufacturing.
