In this study, the size effects on tensile properties and compressive strength of engineered cementitious composites (ECC) were investigated via experimental studies. Plane (2-D) and block (3-D) dogbone-shaped specimens were tested under uniaxial tension to study the size effect on tensile properties. Cubes and cylinders of different sizes were tested under uniaxial compression to study the size effect on compressive strength. The effect of water/binder (w/b) ratio on the compressive strength of ECC was also studied. Five w/b ratios (i.e., 0.20–0.42) were considered to cover a wide strength range. Three polyethylene (PE) fiber volume contents 0%, 1% and 2% were added to cubes for three different sizes (i.e., L = 40 mm, 50 mm and 100 mm) under five w/b ratios. Both of the plane and block dogbone-shaped specimens exhibited strain-hardening behavior accompanied with multiple micro-cracks under uniaxial tension. The size effects on the tensile properties of ECC were discussed, and the experimental scaling factors of tensile properties of block specimen to plane specimen were established and compared with the theoretical value. Additionally, the influences of specimen shape and specimen size on the compressive strength of ECC were stressed. The compressive strength of ECC decreased as the increasing specimen size regardless of the w/b ratio. It is also concluded that the compressive strength discrepancy caused by different specimen shape was negligible at 2% fiber volume content when the cube edge length was equal to the cylinder diameter. Furthermore, a size effect law for cubes with a high reliability was proposed based on fracture mechanics, and a correlation between the compressive strength of cube at any size and that of standard cylinder was deduced, providing a helpful strength conversion reference for ECC.

在这项研究中，通过实验研究了尺寸对工程水泥复合材料（ECC）的拉伸性能和抗压强度的影响。在单轴拉伸下测试平面（2-D）和块状（3-D）狗骨形样品，以研究尺寸对拉伸性能的影响。在单轴压缩下测试了不同尺寸的立方体和圆柱体，以研究尺寸对压缩强度的影响。还研究了水/粘合剂（w / b）比对ECC抗压强度的影响。五个w / b的比率（即0.20-0.42）被认为可以覆盖很宽的强度范围。将三种聚乙烯（PE）纤维体积含量分别为0％，1％和2％的三种不同尺寸（即L  = 40 mm，50 mm和100 mm）在5个以下的立方体中添加w / b比。平面和块状的狗骨形样品在单轴张力下均表现出应变硬化行为，并伴有多个微裂纹。讨论了尺寸对ECC拉伸性能的影响，建立了块状试样对平面试样拉伸性能的实验比例因子，并将其与理论值进行了比较。另外，强调了试样形状和试样尺寸对ECC抗压强度的影响。ECC的抗压强度随着样品尺寸的增加而降低，而与w / b无关比。还得出结论，当立方体边缘长度等于圆柱体直径时，在2％的纤维体积含量下，由不同样品形状引起的抗压强度差异可以忽略不计。此外，基于断裂力学，提出了具有高可靠性的立方体的尺寸效应定律，推导了任意尺寸的立方体的抗压强度与标准圆柱体的抗压强度之间的相关性，为ECC的强度转换提供了有益的参考。