Research on the Effects of the Water-Binder Ratio and Fiber Content on the Tensile and Bending Mechanical Properties of ECCs.

Engineered cementitious composites (ECCs) are a type of high-performance composite material, but in practical applications, ECCs that combine high strength with high toughness have greater development potential. Moreover, there is currently no unified standard or method for assessing the bending toughness of ECCs. This study is based on the Modified Andreasen and Andersen model (MAA) design ratio of the closest packing theory to investigate the effect of changes in the water-binder ratio and fiber content, where the water-binder ratio is taken as 0.19, 0.22, and 0.25, and the fiber content is taken as 1.0%, 1.5%, and 2.0%, respectively, to improve the comprehensive performance of ECCs. Information about tensile strength, bending strength, tensile toughness, and bending toughness is examined. Three different ways to measure bending toughness are compared and improved; the energy factor Ems is used to measure bending toughness, and a response surface methodology is used to design and test the best mix ratio. The results indicate that when the water-binder ratio is 0.22 and the fiber content is 1.9%, the performance is optimal. Compared with the prediction group, the measured group presented an increase in tensile strength of 2.64%, a decrease in bending strength of 3.39%, an increase in tensile toughness of 3.22%, and an increase in the energy factor Ems of 1.21%. This finding indicates that the response surface optimization improved the performance of the ECCs in various aspects.