Investigation on the flexural toughness evaluation method and surface cracks fractal characteristics of polypropylene fiber reinforced cement-based composites

Abstract

In this study, the compressive and flexural properties of polypropylene fiber reinforced cement-based composites are investigated, and a suitable method for evaluating the flexural toughness is proposed. The compressive strength, flexural strength, deflection, flexural toughness, and equivalent flexural toughness ratio are also measured. The results indicate that the addition of 2 % polypropylene fiber and 60 % fly ash into matrix facilitates an improvement in strength, and such a cement matrix shows better crack resistance and flexural toughness than ordinary concrete. JSCE-SF4 and ASTM C1609 methods are the main methods for calculating the flexural toughness, but their single calculation process limits the application range. Therefore, based on JG/T 472–2015, a simple method which is not limited by deformation and can ignore the influence of load fluctuation, is proposed to evaluate the load carrying capacity and flexural toughness of engineered cementitious composites (ECC) in the strain-hardening stage. Furthermore, it is verified that the surface cracks of specimens under flexural load exhibit fractal characteristics, and the “fractal dimension” can be used to describe the distribution of surface cracks. Besides, a quantitative relationship is established between the fractal dimension of surface cracks and the flexural toughness evaluation parameters obtained by the improved JG/T 472–2015 method, which indicates that the fractal dimension of surface cracks can be used to characterize the flexural properties of ECC.