Elsevier

Structures

Volume 31, June 2021, Pages 330-340
Structures

Experimental study on mechanical properties and damage mechanism of basalt fiber reinforced concrete under uniaxial compression

https://doi.org/10.1016/j.istruc.2021.01.071Get rights and content

Abstract

In this study, the effects of basalt fiber content on the uniaxial compressive mechanical properties and damage of concrete were investigated. Acoustic emission (AE) technology was adopted to collect the AE characteristic parameters (ringing count and energy) in the entire loading process, and the change trend of the characteristic parameters from initial compression to final complete failure was analyzed during the uniaxial compression test of basalt fiber-reinforced concrete (BFRC). 3D-digital image correlation was used to record the surface strain field and track the surface crack development in real time. Research results show that a proper amount of basalt fiber (6 kg/m3) can improve the compressive strength of concrete and reduce the density and intensity of AE characteristic parameters. The change in AE characteristic parameters is closely related to the stress–strain curve of BFRC and includes three stages, namely, initial compaction, stable crack propagation, and unstable crack propagation stages. With the increase in basalt fiber content, AE events are dispersed in concrete, effectively weakening the local damage. The strain contours show that adding a proper amount of basalt fiber can delay the early cracking and reduce the transverse strain of concrete. At the same time, the long cracks on the surface of BFRC gradually transform into many microcracks with the increase in basalt fiber content.

Introduction

Concrete is widely used in engineering construction because of its low cost, high compressive strength, good plasticity, and durability. However, the performance of traditional concrete cannot meet the needs of engineering construction with the development of economy and society and the emergence of engineering structures, such as super high-rise buildings, long-span suspension bridges, underground structures, and deep roadways. Therefore, the comprehensive performance of concrete should be improved to adapt to the development of today’s society while addressing the technical construction problems.

Since the middle of the 20th century, the addition of fiber materials to concrete was proposed to improve its mechanical properties of concrete. Researchers have conducted several studies on various fiber reinforced concrete. In 1973, ACI Committee 544 [1] first summarized the development of fiber reinforced mechanics of ordinary concrete with metal, glass, plastic, and natural fibers and systematically outlined the mixing ratio, placement, and practical and potential application technologies of fibers. Islam et al. [2] studied the effects of different amounts of jute fiber on the compressive and splitting tensile properties of concrete. The results indicated that small jute fiber content can promote the hardening properties of concrete. Papakonstantinou et al. [3] explored the mechanical properties of fiber reinforced concrete made from steel fiber extracted from waste tires. The experimental results showed that the decrease in compressive strength is obviously greater than that in splitting tensile strength with the increase in fiber content. Hilles et al. [4] found that the addition of alkali-resistant glass fiber improves the splitting tensile and flexural strengths of concrete and systematically expounded the failure morphology of alkali-resistant glass fiber reinforced concrete. Jirawattanasomkul et al. [5] conducted compression tests on concrete columns made of three types of natural fibers, namely, jute, hemp, and cotton. The results manifested that natural fiber is effective and suitable for improving the strength of concrete. Alsayed et al. [6] performed a series of tests on the flexural strength of glass fiber reinforced concrete. The results showed that glass fiber can improve the flexural capacity of concrete-reinforced beams. In the beginning of the 21st century, a type of green inorganic environmental protection fiber (basalt fiber) was applied to engineering practice. Basalt fiber has high tensile strength and elastic modulus [7], [8], [9] which can effectively improve the strength [10], [11] ductility, fire resistance and durability [12], [13], [14] of concrete. Zhang et al. [15] investigated the influence of basalt fiber on the impact failure mechanism of concrete through the falling ball impact test of concrete beam. Basalt fiber forms a 3D space system in concrete with the increase in basalt fiber content, thereby expanding the propagation range of impact stress wave and improving the initial cracking and impact resistance of concrete.

At present, the macroscopic mechanical properties, such as compressive [16] splitting tensile [17], [18] and flexural strengths [19], [20] of various fiber reinforced concrete have been intensively studied. However, the research on the damage mechanism of fiber reinforced concrete is still a hot topic. Li et al. [21] used acoustic emission (AE) technology to conduct three bending tests on polyvinyl alcohol fiber reinforced concrete. The damage mechanism of polyvinyl alcohol fiber reinforced concrete was determined on the basis of the correlation diagram of characteristic parameters obtained using the AE instrument. Aggelis et al. [22] used AE characteristic parameters, such as signal amplitude and average frequency, to characterize the fracture process of steel fiber reinforced concrete in four-point bending failure and found that the AE method can be used to characterize the damage mechanism of concrete and serve as an early warning of material failure. The above research mainly characterizes the damage of concrete through AE characteristic parameters, but failed to visually observe the surface damage changes. The investigation of the damage mechanism was relatively simple. In response to the above-mentioned problems, this study clearly shows the surface crack propagation behavior of BFRC through the strain contours of 3D-DIC technology. At the same time, combined with acoustic emission technology to monitor internal damage, a relatively complete damage mechanism of basalt fiber reinforced concrete has been established.

In shaft and roadway engineering, there are high requirements for the use of all kinds of materials. Especially in the excavation of deep shaft and roadway, the support of shaft and roadway walls is an important construction step in excavation, where high-quality sprayed concrete plays a decisive role in shaft and roadway support. Therefore, improving the comprehensive performance and adaptability of sprayed concrete in complex conditions should be explored. In this study, the compressive property, compressive damage mechanism, and crack propagation behavior of sprayed concrete mixed with basalt fiber are thoroughly and comprehensively investigated. The influence of basalt fiber content on the compressive strength, strain, and other mechanical properties of concrete can be obtained from the stress–strain curves. Through the changing trend of AE characteristic parameters with the basalt fiber content, the strengthening mechanism of fiber material and the damage mechanism of concrete are explained. 3D-digital image correlation (3D-DIC) is used to analyze the transverse strain on the surface of BFRC and systematically describe the crack propagation behavior at different loading levels in the compression damage process. Results can serve as a reference for the support of deep shaft and roadway engineering.

Section snippets

Raw materials

The main raw materials of the specimens are cement, coarse aggregate, sand, water, and basalt fiber. The detailed parameters of raw materials are shown in Table 1.

Specimen preparation

Table 2 shows the mixture proportions of five BFRC groups. The gravels are soaked in water for half an hour and then collected for use. They are divided into five pouring groups in accordance with different fiber contents. The pouring process is shown in Fig. 3. The mixed fiber concrete is poured into a mold with a si ze of

BFRC strength and failure characteristics

As shown in Fig. 8, the stress–strain curves of five types of BFRC under uniaxial compression show the same change trend. The uniaxial compression curves are divided into four stages. The four stages of the stress–strain curve of SC0 are divided in detail as shown Fig. 9. The first stage is the pore compaction stage, where the curve is characterized by a continuous increase in strain, a small increase in stress, and evident nonlinear deformation. The second stage is the elastic compression

Analysis of AE characteristic parameters

The AE probe attached to the surface of the specimen is used to detect AE signal caused by the microcracks [23]. The AE probe converts the mechanical waves generated by the AE source into continuous electrical signals, which are inputted into the AE processor through the preamplifier and stored in the memory for subsequent analysis and display after signal processing. AE mainly analyzes and deals with the damage characteristics of a specimen through the characteristic parameters [24] such as

Development of cracks

The transverse strain contours of five BFRC groups at different loading levels are shown in Fig. 12, including the first appearance of cracks and crack propagation at loading level of 80%, 90%, and 100% P0.The initial cracks of the five specimen groups occur at 57.3%, 60.8%, 72.5%, 65.7%, and 61.7% P0, respectively. The proper amount of basalt fiber can delay the early cracking of concrete. However, the cracking time of BFRC will be advanced with the excessive addition of basalt fiber content.

Conclusion

In this study, the effects of different basalt fiber contents on the compressive performance, damage mechanism, and crack propagation behavior of BFRCs are investigated. The conclusions are summarized as follows:

  • 1.

    The proper amount of basalt fiber (6 kg/m3) improves the compressive strength and peak strain of concrete. However, excessive basalt fibers reduce the compressive strength of concrete, and the peak strain remains unchanged at 0.0145.

  • 2.

    The change in AE characteristic parameters (ringing

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (No. 51974316).

References (26)

Cited by (0)

View full text