This study deals with (a) the development of a prototype 3D printer for concrete structures having a bed size of 1 × 1 × 1 m for a laboratory testing and (b) laboratory testing of cementitious materials with different design mixes to find their suitability and efficacy for the developed 3D printer. In this printer, a program with the concept of computer numerical controlled milling was adopted to control the nozzle motion using an easy graphic user interface program. The experiment was carried out to test mechanical control and proper material properties of the printer. Thus, the optimum values of water-cement ratio of cementitious materials for the 3D concrete printer were determined by experimental trials. Also, the adequate viscosity of the material for layering and dispensing is determined by a slump-flow test. The suitable size of sands for the dispensing system was found through the trials. However, shrinkage cracks occurred during the hardening process for the paste and mortar that polyvinyl alcohol fibers are added to prevent the cracking and build an improved quality 3D printed structure. After suitable and efficient mix ratio is found, compressive strength is measured for the mechanical property. The experiments demonstrated possibility of printing concrete structure using the 3D printer.

中文翻译：

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混凝土结构 3D 打印机的开发：水泥材料的实验室测试

本研究涉及 (a) 开发用于实验室测试的床尺寸为 1 × 1 × 1 m 的混凝土结构原型 3D 打印机，以及 (b) 对具有不同设计组合的胶结材料进行实验室测试，以发现其适用性和开发的 3D 打印机的功效。在这台打印机中，采用了具有计算机数控铣削概念的程序，使用简单的图形用户界面程序来控制喷嘴运动。进行该实验是为了测试打印机的机械控制和适当的材料特性。因此，用于 3D 混凝土打印机的胶凝材料的水灰比的最佳值是通过实验确定的。此外，用于分层和分配的材料的足够粘度由坍落流测试确定。通过试验找到了适合分配系统的沙子尺寸。然而，添加聚乙烯醇纤维以防止开裂并构建质量更高的 3D 打印结构的糊料和砂浆在硬化过程中会出现收缩裂缝。在找到合适和有效的混合比后，测量力学性能的抗压强度。实验证明了使用 3D 打印机打印混凝土结构的可能性。