A significant amount of work has focused on the development of concrete mixtures for digital manufacturing (3D printing), and their rheological and mechanical properties. However, for extrusion-based layered manufacturing, it is also important to select the appropriate printing parameters that have the potential to impact the performance of 3D printed elements. Among the many such parameters, this paper places emphasis on layer height, which has a direct bearing on rheology requirements, print quality, overall printing time, and interlayer bonding. Specifically, this paper examines the effects of layer height (5, 10, and 15 mm layer heights corresponding to 25, 50, and 75% of the nozzle diameter, which is 20 mm) on the flexural strength and fracture properties of 3D printed beams. Flexural and fracture properties indicate that smaller layer heights are beneficial for unreinforced and fiber-reinforced 3D printed mortars, even though this results in greater number of interfaces and longer printing times. A small amount of steel fiber reinforcement is shown to be useful in eliminating the negative effects of weak interfaces on the measured bulk properties, with average flexural strengths higher by 30–40% and fracture toughness and crack tip opening displacement higher by almost 30% as compared to plain mixtures. Strain energy release rates, digital image correlation, and optical images/micrographs are used to explain crack propagation in layered 3D printed mortars under unnotched four-point, and notched three-point bending.

大量工作集中在开发用于数字制造（3D 打印）的混凝土混合物及其流变和机械性能。然而，对于基于挤出的分层制造，选择合适的打印参数也很重要，这些参数有可能影响 3D 打印元素的性能。在众多此类参数中，本文重点关注层高，它直接关系到流变要求、印刷质量、整体印刷时间和层间粘合。具体而言，本文研究了层高（5、10 和 15 毫米层高对应喷嘴直径的 25、50 和 75%，即 20 毫米）对 3D 打印梁的弯曲强度和断裂性能的影响. 弯曲和断裂特性表明，较小的层高有利于未增强和纤维增强的 3D 打印砂浆，尽管这会导致更多的界面和更长的打印时间。少量钢纤维增强材料可用于消除弱界面对测量的整体性能的负面影响，平均弯曲强度提高 30-40%，断裂韧性和裂纹尖端张开位移提高近 30%，如与普通混合物相比。应变能释放率、数字图像相关性和光学图像/显微照片用于解释层状 3D 打印砂浆在无缺口四点弯曲和带缺口三点弯曲下的裂纹扩展。尽管这会导致更多的接口和更长的打印时间。少量钢纤维增强材料可用于消除弱界面对测量的整体性能的负面影响，平均弯曲强度提高 30-40%，断裂韧性和裂纹尖端张开位移提高近 30%，如与普通混合物相比。应变能释放率、数字图像相关性和光学图像/显微照片用于解释层状 3D 打印砂浆在无缺口四点弯曲和带缺口三点弯曲下的裂纹扩展。尽管这会导致更多的接口和更长的打印时间。少量钢纤维增强材料可用于消除弱界面对测量的整体性能的负面影响，平均抗弯强度高出 30-40%，断裂韧性和裂纹尖端张开位移高出近 30%，如与普通混合物相比。应变能释放率、数字图像相关性和光学图像/显微照片用于解释层状 3D 打印砂浆在无缺口四点弯曲和带缺口三点弯曲下的裂纹扩展。与普通混合物相比，平均弯曲强度高出 30-40%，断裂韧性和裂纹尖端张开位移高出近 30%。应变能释放率、数字图像相关性和光学图像/显微照片用于解释层状 3D 打印砂浆在无缺口四点弯曲和带缺口三点弯曲下的裂纹扩展。与普通混合物相比，平均弯曲强度高出 30-40%，断裂韧性和裂纹尖端张开位移高出近 30%。应变能释放率、数字图像相关性和光学图像/显微照片用于解释层状 3D 打印砂浆在无缺口四点弯曲和带缺口三点弯曲下的裂纹扩展。