For a single batch material, time intervals and nozzle standoff distances between two subsequent layers are two critical printing parameters that influence the mechanical performance of the printed concrete. This paper presents an experimental and numerical study to investigate the impacts of these printing parameters on the interlayer bond strength of the 3D printed limestone and calcined clay-based cementitious materials. All samples were manufactured by a lab-scale 3D printer equipped with a hybrid back- and down-flow nozzle (rectangular opening). The uniaxial tensile test was employed to quantify the interface adhesion of printed specimens. Moreover, the greyscale value image of microstructure, as well as the air void content and distribution of the printed specimens were acquired by X-ray computed tomography and characterized by image analysis. The experimental results showed that extending the time interval between construction of two layers could decrease the bond strength, whereas only increasing the nozzle standoff distance exhibited limited effects on that. The weak bond strength could be attributed to the high local porosity at the interface of the specimen. Additionally, numerical simulations of the uniaxial tensile test were conducted using a 2D lattice fracture model, which can predict the bond strength of printed specimens for different void content in the interface layer.

对于单批物料，两个后续层之间的时间间隔和喷嘴间距是影响印刷混凝土机械性能的两个关键印刷参数。本文提供了一项实验和数值研究，以研究这些印刷参数对3D打印石灰石和煅烧粘土基胶凝材料的层间粘结强度的影响。所有样品均由配备了反向和向下混合喷嘴（矩形开口）的实验室规模的3D打印机制造。单轴拉伸试验用于量化印刷样品的界面粘附力。此外，微观结构的灰度值图像，通过X射线计算机断层摄影术获得印刷样品的气孔含量和分布，并通过图像分析对其进行表征。实验结果表明，延长两层结构之间的时间间隔可能会降低粘结强度，而仅增加喷嘴支座距离会对此产生有限的影响。弱的结合强度可以归因于样品界面处的高局部孔隙率。另外，使用二维晶格断裂模型进行了单轴拉伸试验的数值模拟，该模型可以预测界面层中不同孔隙含量的印刷样品的粘结强度。而仅增加喷嘴支座距离对它的影响有限。弱的结合强度可以归因于样品界面处的高局部孔隙率。另外，使用二维晶格断裂模型进行了单轴拉伸试验的数值模拟，该模型可以预测界面层中不同孔隙含量的印刷样品的粘结强度。而仅增加喷嘴支座距离对它的影响有限。弱的结合强度可以归因于样品界面处的高局部孔隙率。另外，使用二维晶格断裂模型进行了单轴拉伸试验的数值模拟，该模型可以预测界面层中不同孔隙含量的印刷样品的粘结强度。