Development of a design method for the fracture performance of steel fiber-reinforced concrete by considering steel fiber characteristics and aggregate gradation

In this study, a design method has been developed, which considers the characteristics of steel fiber and aggregate gradation, for the fracture performance of steel fiber-reinforced concrete. This design method requires only one specimen type and test specification, and input of the characteristic parameters of the steel fiber, the characteristic particle size of the concrete aggregate, the peak load of specimen under static loading, and the sizes and types of specimens. According to the calculation process of this design method, the fracture toughness, and the tensile strength, of SFRC can be determined simultaneously. This design method can be used to determine the fracture performance of SFRC without size effect. By introducing the characteristic parameters of steel fiber and the characteristic particle size of concrete aggregate have been introduced into the specific calculation formula of fictitious crack growth of SFRC, a design method has been developed, which considers the coupling effect of steel fiber characteristics and aggregate gradation, for a simultaneous determination of the fracture toughness and the tensile strength of a SFRC. By applying the design method developed in this study to 15 different proportions of SFRC three-point bending specimens with different volumes of steel fiber, aggregate gradations, and water -cement ratios, the fracture toughness and the tensile strength of the SFRC have been determined simulta-neously. The determined values are in good agreement with the experimental tensile strength and fracture toughness calculated by the size effect model. Using the fracture toughness and the tensile strength obtained by the normal distribution method, a complete failure curve for SFRC with 95% reliability has been constructed, and the size meeting the requirements of linear elastic fracture mechanics has been obtained. Simultaneously, the prediction curves of fracture toughness and tensile strength determined by the design method developed in this study are basically consistent with those determined by the normal distribution method. This further verifies the correctness and rationality of the fracture performance design method for SFRC developed in this study. The simplified analytical expressions between the peak load and the fracture toughness, and between the peak load and the tensile strength of SFRC have been developed. Based on the simplified analytical expressions, the peak load of the minimum specimen size satisfying linear elastic fracture has been predicted.

Automated summary

A design method has been developed to determine the fracture toughness and tensile strength of steel fiber-reinforced concrete (SFRC) by considering the characteristics of steel fiber and aggregate gradation. The design method was validated through experiments and can be used to construct a complete failure curve for SFRC with high reliability.