Experimental Study on Mechanical Properties and Fractal Dimension of Pore Structure of Basalt–Polypropylene Fiber-Reinforced Concrete

Abstract

This study investigates the effects of basalt–polypropylene fibers on the compressive strength and splitting tensile strength of concrete and calculates the fractal dimension of the pore structure of concrete by using a fractal model based on the optical method. Test results reveal that hybrid fibers can improve the compressive strength and splitting tensile strength of concrete, and the synergistic effect of the hybrid fibers is strongest when the contents of basalt fiber (BF) and polypropylene fiber (PF) are 0.05% each, and that the maximum increments in compressive strength and splitting tensile strength are 5.06% and 9.56%, respectively. The effect of hybrid fibers on splitting tensile strength is greater than on compressive strength. However, hybrid fibers have adverse effects on mechanical properties when the fiber content is too high. The pore structure of basalt–polypropylene fiber-reinforced concrete (BPFRC) exhibits obvious fractal characteristics, and the fractal dimension is calculated to be in the range of 2.297–2.482. The fractal dimension has a strong correlation with the air content and spacing factor: the air content decreases significantly whereas the spacing factor increases with increasing fractal dimension. In addition, the fractal dimension also has a strong positive correlation with compressive strength and splitting tensile strength. Therefore, the fractal dimension of the pore structure can be used to evaluate the microscopic pore structure of concrete and can also reflect the influence of the complexity of the pore structure on the macroscopic mechanical properties of concrete.

Investigation on the microstructural characteristics and quasi-static puncture resistance of both domesticated and wild silkworm cocoons

“…15 The increase in fractal dimension of porous materials is associated with the increase of solid packing density and the more complex distribution of the solid phase, as well as the decrease of the porosity, the average pore size, the decrease of the large pore numbers and the increase of small pores and pore surface area. 12,32,33 In this study, using a linear regression method, fractal dimension was found to be negatively correlated with porosity (R 2 ¼ 0.90) and normal density (R 2 ¼ 0.67) of cocoon samples, and positively correlated with fiber intersectional density (R 2 ¼ 0.86). This was in accordance with previous studies that also discovered a higher correlation between fractal dimension and porosity for the fiber assemblies and fiber-reinforced composites.…”

“…In addition, the evenly distributed internal stress in the cocoons also prevented concentration of premature stress. 12 These could explain why both F max and puncture energy showed an obvious increasing trend with the increasing fractal dimensions. It can be concluded that fractal dimension could well predicate the anti-puncture performance of silkworm cocoons.…”

“…the maximum distance between any adjacent object spheres) and porosity of porous materials. 12,13 In addition, it has a strong relationship with the compressive strength or tensile strength of fiber-reinforced composites. 12,14,15 These studies evidently proved that fractal dimension could well describe the microstructure and the mechanical properties of fiber composites.…”

“…12,13 In addition, it has a strong relationship with the compressive strength or tensile strength of fiber-reinforced composites. 12,14,15 These studies evidently proved that fractal dimension could well describe the microstructure and the mechanical properties of fiber composites. 15 Thus, fractal theory was adopted to study the microstructural characteristics of silkworm cocoons and predict their mechanical properties.…”

Effects of Aggregate Micro Fines (AMF), Aluminum Sulfate and Polypropylene Fiber (PPF) on Properties of Machine-Made Sand Concrete

“…In order to modify the properties of concrete, the polypropylene fiber (PPF) could be added [17][18][19][20][21][22][23][24][25][26][27][28], and the PPF was found to be very effective in improving the crack resistance compared to other methods. The addition of PPF was found to decrease the workability [17] and increase the compressive strength [29][30][31][32], crack resistance [33][34][35], and durability [31,[36][37][38][39][40][41] given that the PPF was within an optimum content.…”