Study on the Fracture Toughness of Polypropylene\u2013Basalt Fiber-Reinforced Concrete

Ninghui Liang,Zuliang Zhong,Shuo Tian,Lianxi Ren,Zhiyun Deng,Xinrong Liu,Ru Yan

doi:10.1186/s40069-021-00472-x

Abstract

To study the hybrid effects of polypropylene fiber and basalt fiber on the fracture toughness of concrete, 13 groups of notched concrete beam specimens with different fiber contents and mass ratios were prepared for the three-point bending test. Based on acoustic emission monitoring data, the initiation cracking load and instability load of each group of specimens were obtained, and the fracture toughness parameters were calculated according to the double-K fracture criterion. The test results show that the basalt fiber-reinforced concrete has a greater increase in initial fracture toughness, and the toughness of coarse polypropylene fiber-reinforced concrete is more unstable. Moreover, after the coarse polypropylene fiber content reaches 6 kg/m3 and the basalt fiber content reaches 3 kg/m3, increasing the content will not significantly improve the fracture toughness of the concrete. The polypropylene–basalt fiber will produce positive and negative effects when mixed, and the mass ratio of 2:1 was optimal. Finally, the fitting analysis revealed that the fracture process of polypropylene–basalt fiber-reinforced concrete (PBFRC) can be objectively described by the bilinear softening constitutive curve improved by Xu and Reinhardt.

Highlights

With the emergence of large-span beams, super highrise buildings and mass concrete structures, the requirements for concrete strength and ductility are increasing
Incorporating fiber makes the mixture of each group of polypropylene–basalt fiber-reinforced concrete (PBFRC) specimens become denser, which shows that the Vebe Consistency (VC) time becomes larger
Compared with the minimum content of coarse polypropylene fiber and basalt fiber which are 6 kg/m3 and 3 kg/m3, when the maximum content of polypropylene fiber and basalt fiber reaches 9 kg/m3 and 6 kg/m3, the VC time increased by 7.14% and 16.67%, respectively

Summary

Introduction

With the emergence of large-span beams, super highrise buildings and mass concrete structures, the requirements for concrete strength and ductility are increasing. Enhancing toughness and deformation performance have become an important problem to solve when the concrete strength increases, ductility decreases, and brittleness increases. It is one of the effective methods that adding fiber into concrete for improving the tensile. Studies have shown that adding different fibers can improve the toughness of concrete in different manners. Steel fiber improves the strength of concrete, and enhances fracture load and toughness in the fracture process (Abdallah et al, 2016; Chi et al, 2014). Steel fiber has defects, such as high cost, self-importance, easy to rust, and poor workability.

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Results

Conclusion