Research on mechanical characteristics, fractal dimension and internal structure of fiber reinforced concrete under uniaxial compression

Abstract

In this paper, a series of laboratory investigations were carried out to explore the effect of fiber dosage and types on the mechanical properties and failure modes of fiber-reinforced concrete. The concrete specimens with different fiber dosages (0 wt%, 0.4 wt%, 0.8 wt%, or 1.2 wt%) and fiber types (polypropylene, glass and polyacrylonitrile fibers) were prepared and subjected to uniaxial compressive testing. Besides, the industrial computed tomography (CT) scanning was conducted on samples before and after compression to analyze the temporal and spatial evolution of internal micro-cracks. The experimental results show that the uniaxial compressive strength of fiber-reinforced concrete first increased and then decreased as fiber dosage increased. The peak stress of glass fiber-reinforced concrete was higher than those of polypropylene and polyacrylonitrile fiber-reinforced concretes. The peak stress of concrete with 0.8 wt% glass fibers was 39% higher than that of ordinary concrete. The strain of fiber-reinforced concrete linearly increased with fiber dosage increased. Furthermore, the fractal characteristics were investigated in the concrete cracks. The internal and external cracks revealed that the failure mode of fiber-reinforced concrete transitions from shear failure to tensile failure with fiber dosage increased. The extent of bridging effects of the three fiber types on cracks in the concrete could be ranked in descending order as follows: glass fiber > polypropylene fiber > polyacrylonitrile fiber according to the CT scanning results.