Bekaert Michiel, Van Tittelboom Kim, De Schutter Geert
Magnel-Vandepitte Laboratory for Structural Engineering and Building Materials, Department of Structural Engineering and Building Materials, Faculty of Engineering and Architecture, Ghent University, Technologiepark Zwijnaarde 60, B-9052 Ghent, Belgium.
Materials (Basel). 2023 Oct 30;16(21):6972. doi: 10.3390/ma16216972.
Complex concrete elements are typically produced with lost formwork made out of timber or plastic. After usage, these timber or plastic panels are disposed of. This makes complex lost formwork a polluting and high-cost-inducing aspect of concrete construction. A possible solution for this problem could be 3D printing of concrete. This high degree of freedom construction process could easily be used to produce complex formwork. As the formwork stays in place, it has a function during and after the hardening of the inner concrete. Before hardening, the formwork keeps the fresh concrete in place. After hardening, the printed formwork takes the function of a concrete cover. The concrete cover protects the steel reinforcement against aggressive environmental substances such as chlorides and carbon dioxide. To properly execute this function, the printed material and the transition between printed material and inner concrete need to perform at least as well as the inner material. This experimental research investigates the usability of a 3D printed concrete mixture as a concrete cover in a combined concrete structure. The effect of the curing condition as well as two different surface finishing techniques of the printed formwork are taken into account. The effect of the different parameters is compared based on existing service life models. Results indicate that proper curing of the printed formwork is of key importance in order to obtain significant resistance against carbonation- and chloride-induced corrosion. Adjusting the nozzle with side trowels improves the resistance of the printed material against chloride intrusion and carbonation but has only a limited effect on the service life extension.
复杂混凝土构件通常采用由木材或塑料制成的一次性模板生产。使用后，这些木材或塑料面板就会被丢弃。这使得复杂的一次性模板成为混凝土施工中一个造成污染且成本高昂的因素。解决这个问题的一个可能办法是混凝土3D打印。这种具有高度自由度的施工工艺可以轻松用于生产复杂模板。由于模板留在原地，它在内部混凝土硬化期间及之后都发挥作用。在硬化之前，模板将新拌混凝土固定在原位。硬化之后，打印模板起到混凝土保护层的作用。混凝土保护层可保护钢筋免受氯化物和二氧化碳等侵蚀性环境物质的影响。为了恰当地发挥这一功能，打印材料以及打印材料与内部混凝土之间的过渡部分至少要与内部材料表现得一样好。这项实验研究调查了一种3D打印混凝土混合物在组合混凝土结构中作为混凝土保护层的适用性。考虑了养护条件以及打印模板的两种不同表面处理技术的影响。基于现有的使用寿命模型比较了不同参数的影响。结果表明，对打印模板进行适当养护对于获得显著的抗碳化和抗氯化物腐蚀能力至关重要。用抹子调整喷嘴可提高打印材料的抗氯化物侵入和抗碳化能力，但对延长使用寿命的影响有限。
