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Article

Mechanical, Chloride Resistance, and Microstructural Properties of Basalt Fiber-Reinforced Fly Ash–Silica Fume Composite Concrete

by
Yishan Li
,
Yan Liu
* and
Wei Zhang
*
Hebei Key Laboratory of Structural Safety and Low-Carbon Construction for Rural Buildings, Hebei Agricultural University, Baoding 071001, China
*
Authors to whom correspondence should be addressed.
Minerals 2025, 15(4), 348; https://doi.org/10.3390/min15040348
Submission received: 3 March 2025 / Revised: 21 March 2025 / Accepted: 25 March 2025 / Published: 27 March 2025
(This article belongs to the Special Issue Recycling and Utilization of Metallurgical and Chemical Solid Waste)
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Abstract

:
Basalt fiber has advantages in enhancing the mechanical properties of concrete, but the comprehensive effects of fiber content and length, as well as the relationship between mechanical and impermeability performance, remain unclear and require systematic verification. This study aims to quantify the effects of basalt fiber content and length on mechanical properties (compressive strength, tensile strength, and flexural strength) and concrete permeability performance and reveal the underlying mechanisms. The macroscopic performance results indicate the following: (1) the optimum fiber content of compressive strength and flexural strength of basalt fiber-reinforced concrete is 1.5 kg/m3; (2) the optimum content of tensile strength is 1.0 kg/m3; and (3) the impermeability performance of the fiber-reinforced concrete is most significantly improved when the fiber content reaches 1.0 kg/m3 and the fiber length is 18 mm. During the permeability tests, a nonlinear functional relationship exists between two indicators, electric flux and chloride ion migration coefficient. Microscopic analysis showed that mineral admixtures (fly ash and silica fume) promoted the secondary hydration reaction in the cementitious material, generating a significant amount of C-(A)-S-H gels to increase the density of the concrete matrix. After incorporating basalt fibers, they tightly envelop the concrete matrix, reducing the number of internal voids and achieving a synergistic stress-bearing effect with the concrete, confirming that the addition of fibers optimizes the mechanical and impermeability properties of the concrete. This study provides a quantitative reference for the basalt fiber reinforcement design of engineering concrete structures and helps extend the service life of concrete buildings.

1. Introduction

Concrete, the most widely used construction material, comprises inexpensive raw materials and offers simple construction methods, making it a fundamental element of building structures [1,2]. However, its high brittleness and low tensile strength lead to cracking and failure during service, negatively impacting concrete structures’ durability [3]. With the rapid development of the construction industry in recent years, the demand for concrete with specialized properties has continuously increased. Incorporating fibers into concrete has emerged as a technological approach that is gradually being adopted in engineering construction. Fiber-reinforced concrete is a composite material formed by uniformly introducing randomly oriented short fibers into cement-based concrete. The cementitious materials in concrete inherently possess a certain degree of porosity [4]; The fibers’ bridging effect helps reduce the gaps between aggregates, influencing the internal pore structure of the concrete. This, in turn, enhances the mechanical properties of the concrete by minimizing the propagation of shrinkage cracks [5,6], restricts the width of cracks in cracking concrete, improves the mechanical properties and impermeability of the concrete, and extends the service life of concrete structures [7,8].
Basalt fiber is a new type of inorganic green fiber made from natural basalt after it is melted at high temperatures. Its advantages include chemical stability, excellent insulation properties, strong corrosion resistance, good heat resistance, and high cost-effectiveness [9,10,11,12,13]. Additionally, it maintains a high elastic modulus and tensile strength even under extreme conditions, such as high temperatures, with strength significantly exceeding that of natural and synthetic fibers [14,15]. It is the fourth central high-performance fiber actively developed in China. It is globally recognized that adding chopped basalt fiber into concrete can compensate for its deficiencies [16]. When basalt fibers are incorporated, they bond more effectively with the concrete, inhibiting the development of internal microcracks [17], thus improving the brittleness of concrete. This enhancement boosts the concrete’s mechanical properties, including impact resistance, crack resistance, thermal attack resistance, and corrosion resistance [18,19]. Furthermore, the high silica content in the basalt structure makes basalt fibers highly compatible with the cement matrix [20]. As a result, basalt fiber is gradually becoming a popular material in concrete reinforcement, demonstrating promising development potential [21].
Scholars have conducted comprehensive research on the various properties of basalt fiber-reinforced concrete. Most studies on the durability of basalt fiber-reinforced concrete focus on its resistance to corrosion, freeze–thaw performance, and the effects of acidic and alkaline conditions on its durability [22,23,24,25,26]. Although research on the influence of basalt fiber length and dosage on its impermeability and mechanical properties is also ongoing, it is relatively limited. Table 1 presents the research findings from various scholars over the past decade regarding the effects of basalt fiber length and dosage on the performance of concrete.
Based on the above research findings, the length and dosage of basalt fiber are two critical factors affecting the performance of concrete. In addition, current research mainly focuses on the mechanical properties of concrete, while there is limited research on its permeability. Therefore, conducting experimental studies on the impermeability of basalt fiber-reinforced concrete has practical value and theoretical significance for preventing water infiltration in bridge and road engineering and improving the service life of buildings. This paper takes basalt fiber and fly ash–silica fume composite concrete (the following is referred to as basalt fiber-reinforced concrete) as the research object, selecting two variables: fiber length and dosage, with the same mix proportion and other influencing factors kept constant. On the one hand, the study investigates the impact of fiber length and dosage on the compressive, tensile, and flexural properties of fly ash–silica fume composite concrete. On the other hand, electric flux tests and rapid chloride ion permeability coefficient tests were conducted to investigate the influence of fiber content and length on the impermeability of concrete. The correlation between the metrics obtained from these two different testing methods was explored, providing a reference for applying basalt fiber-reinforced concrete in practical engineering and enhancing its performance in engineering applications.

2. Materials and Methods

2.1. Raw Materials

Fiber: Chosen basalt fiber produced by a company in Hunan. The three specifications of the fiber are shown in Figure 1. The leading technical indicators are shown in Table 2.
Cement: P.O42.5 ordinary Portland cement is used. It is produced by the Concrete Branch of Hebei Construction Group, Baoding, Hebei Province, China.
Mineral additive: in this experiment, Class II fly ash and silica fume produced by Hebei Construction Group Concrete Branch were used, with the main chemical composition as shown in Table 3.
Aggregate: Table 4 and Table 5 show coarse and fine aggregate screening results. The coarse aggregate is gravel with 5–25 mm continuous gradation, and the fine aggregate is medium sand with a fineness modulus of 2.9.

2.2. Test Scheme and Mix Proportion Design

The experiment investigates the effects of basalt fiber length and content on concrete’s mechanical and impermeability properties. Basalt fiber lengths of 6 mm, 12 mm, and 18 mm, with fiber contents of 0.5 kg/m3, 1.0 kg/m3, and 1.5 kg/m3, were used to prepare basalt fiber-reinforced concrete, which was then subjected to compressive strength tests, tensile strength tests, flexural strength tests, electrical flux tests, and rapid chloride ion permeability tests. Charts were plotted with fiber length and content as variables by analyzing the data obtained from these tests. The concrete without fiber addition served as the reference concrete (RC), allowing a comparison to determine whether basalt fiber-reinforced concrete’s mechanical and permeability properties were improved relative to the baseline concrete without fibers.
In the experiment, the length and content of basalt fiber were used as variables, and the reference group with fiber content of 0 was set as the control. The fiber content was 0.5 kg/m3, and the fiber length was 6 mm, 12 mm, and 18 mm, respectively. B0.5–6, B0.5–12, B0.5–18; on this basis, the fiber content was increased to 1.0 kg/m3, 1.5 kg/m3 of B1.0–6, B1.0–12, B1.0–18, B1.5–6, B1.5–12, B1.5–18. The mix design is shown in Table 6 below.

2.3. Testing

2.3.1. Mechanical Performance Test

The mechanical properties test was carried out according to the <<Standard for testing methods of physical and mechanical properties of concrete>> (GB/T50081-2019) [36]. The fiber-reinforced concrete’s compressive, tensile, and flexural strengths at 7 day and 28 day were measured after the concrete blocks were placed in the curing room at 20 °C and a relative humidity of 95% for 7 day and 28 day. In each group, 60 cube test blocks of dimensions 100 mm × 100 mm × 100 mm were made for the cube compressive test, and 60 cube test blocks of dimensions 150 mm × 150 mm × 150 mm were made for the splitting tensile test. Compressive and tensile tests were performed on a YAW-2000D pressure testing machine. The equipment is produced by Hebei Sanyu Testing Machine Co., Ltd., Cangzhou, Hebei Province, China. Flexural tests of 60 prism specimens with dimensions of 100 mm × 100 mm × 400 mm were carried out. The four-point bending flexural strength test was performed on an E45.205 electronic universal testing machine. The equipment is produced by Jinan Zhong Lu Chang Testing Machine Manufacturing Co., Ltd., Jinan, Shandong Province, China. The loading was controlled using computer software until the specimen broke. The failure loads of the three test blocks in each group were recorded, and the average flexural strength was calculated.

2.3.2. Impermeability Test

The chloride permeability test evaluates the resistance to chloride ion penetration of fiber-reinforced concrete through two different test methods: the electric flux method, which is based on the standard of the <<Concrete chloride ion electric flux meter>> (JG/T261-2009) [37], and the rapid chloride ion permeability coefficient method, which is based on the standard <<Concrete chloride ion diffusion coefficient meter>> (JG/T262-2009) [38]. These two methods have yielded two key parameters of the electric flux and chloride ion diffusion coefficient of fiber-reinforced concrete, and these parameters have been studied and analyzed in depth.
The electric flux and rapid chloride ion permeability methods use the CABR-RCMP concrete electric flux tester, the instrument is produced by Beijing Jianyan Kunlun Technology Co., Ltd.in Beijing, China. as shown in Figure 2a. The tester combines the CABR-RCM6 concrete chloride ion diffusion coefficient tester and the CABR-RCP6 concrete chloride ion electric flux tester. The device’s function was to measure the electric flux and chloride ion diffusion coefficient. The test piece used was a cylindrical test piece with a diameter of 100 mm and a height of 50 mm. It was removed for testing after 28 day of curing in the room. When measuring the electric flux and chloride ion permeability coefficient, the three test blocks are in one group, as shown in Figure 2b,c below, and the average value is taken after measurement.

3. Results and Discussion

3.1. Compression Test

The 7 day and 28 day compressive strength of basalt fiber-reinforced concrete with different lengths and content is shown in Figure 3.
As shown in Figure 3, the compressive performance of the concrete improved with the addition of basalt fibers.
The compressive strength of the fiber-reinforced concrete at 7 and 28 days was higher than that of the reference concrete without fibers. The 28-day compressive strength of the reference concrete (B0) was 62.3 MPa. With the fiber content kept constant, the 28-day compressive strength of the B0.5–6, B0.5–12, and B0.5–18 groups, with a fiber content of 0.5 kg/m3, increased by 10.27%, 11.40%, and 12.36%, respectively, compared to the B0 group. This indicates that as the fiber length increased from 6 mm to 18 mm, the compressive strength of the fiber-reinforced concrete gradually improved. Similarly, the compressive strength increased as the fiber content increased when the fiber length was fixed, with a relatively smooth linear growth throughout the process. The maximum compressive strength was achieved when the fiber length was 18 mm and the fiber content was 1.5 kg/m3, where the 7-day and 28-day compressive strengths of the basalt fiber concrete were 13.60% and 18.94% higher than that of the reference concrete, respectively.
Incorporating basalt fibers with different contents and lengths reduced the internal porosity of the concrete and improved its density, thereby enhancing its ability to withstand external pressure. Since concrete itself already has excellent compressive strength, the improvement in the compressive performance of the fiber-reinforced concrete was relatively modest.

3.2. Tensile Test

The tensile strength of basalt fiber-reinforced concrete with different lengths and content at 7 day and 28 day is shown in Figure 4.
As shown in Figure 4, incorporating basalt fibers increases concrete tensile strength at 7 and 28 days compared to plain concrete. The tensile strength of the B0 group at 7 days and 28 days are 4.37 MPa and 5.77 MPa, respectively. The concrete tensile strength reaches its peak when the fiber length is 18 mm and the dosage is 1.0 kg/m3, with values of 5.85 MPa and 7.93 MPa at 7 and 28 days, respectively, representing an increase of 33.87% and 37.43% compared to the B0 group.
The B0.5–6, B0.5–12, and B0.5–18 groups show tensile strength increases of 13.17%, 28.42%, and 34.66%, respectively, compared to the control group when the fiber dosage is 0.5 kg/m3. Therefore, under a fixed fiber dosage, as the fiber length increases, the tensile strength of the concrete also improves. The B0.5–6, B1.0–6, and B1.5–6 groups show increases of 13.17%, 19.93%, and 13.86%, respectively, compared to the B0 group when the fiber length is 6 mm, with the B1.0–6 exhibiting the highest tensile strength. Based on this analysis, the tensile strength of the concrete increases as the fiber dosage increases when the fiber length remains constant, reaching a specific peak value before decreasing.
Adding basalt fiber can improve the integrity of the internal structure of concrete. When the splitting tensile test is carried out, with the increase of the external tension, the evenly distributed fibers will disperse a part of the external force until the fibers are destroyed and disconnected. However, with the increase of the fiber content, the fibers of the concrete’s failure surface to resist the external tension also increase so that the early tensile strength will increase with the content increase. However, when the content of basalt fiber in concrete is too high, it is challenging to maintain a uniform state of distribution in concrete, and the disorderly distribution is bound to lead to a decrease in the integrity of the internal structure of concrete and a reduction in tensile strength.

3.3. Flexural Test

The flexural strength of basalt fiber-reinforced concrete with different lengths and content is shown in Figure 5.
As shown in Figure 5, the flexural strength at 7 and 28 days has increased compared to the B0 group. The flexural strength of the B0 group concrete at 28 days is 3.76 MPa. The flexural strengths of the B0.5–6, B0.5–12, and B0.5–18 groups are 3.93 MPa, 4.11 MPa, and 4.36 MPa when the fiber content is kept constant at 0.5 kg/m3, respectively, representing increases of 4.52%, 9.31%, and 15.96% over the B0 group. It can be observed from the numerical changes that as the fiber length increases from 6 mm to 18 mm, the flexural strength of the concrete also increases gradually. The flexural strengths of the B0.5–6, B1.0–6, and B1.5–6 groups are 3.93 MPa, 4.26 MPa, and 4.53 MPa, respectively, corresponding to increases of 4.52%, 13.30%, and 20.48% over the B0 group, when the fiber length is kept constant at 6 mm. The flexural strength also increases gradually with the fiber content. Based on these changes, the peak flexural strength is achieved in the B1.5–18 group, where the flexural strength reaches 4.84 MPa, which is 28.72% higher than the reference group.
The basalt fiber lengths selected for the experiment range from 6 to 18 mm. Within this length range, the basalt fibers can firmly bond with the concrete matrix and possess excellent ductility. Therefore, when external loads are applied to the concrete specimens, the basalt fibers can help to share part of the external load, reduce stress concentration in the concrete, and enable the combined load-bearing behavior of the fibers and concrete, thus improving the flexural strength and optimizing the flexural performance of the concrete.

3.4. Chloride Permeability Test

3.4.1. Electric Flux Test

The measured electric flux results are shown in Figure 6.
As shown in Figure 6, the electric flux for the B0 group is 244.78 C. The fiber content is kept constant at 1.0 kg/m3; the groups B1.0–6, B1.0–12, and B1.0–18 show reductions of 47.40%, 52.70%, and 57.83%, respectively, compared to the B0. The electric flux of basalt fiber-reinforced concrete decreases from 128.76 C to 103.22 C as the fiber length increases, reaching the minimum value when the fiber length reaches 18 mm. Compared with the B0, the B0.5–6, B1.0–6, and B1.5–6 groups decreased by 31.96%, 47.40%, and 18.30% when the fiber length remained unchanged at 6 mm. The electric flux decreases first and then increases as the fiber content continuously increases, with the electric flux reaching the lowest point when the fiber content reaches 1.0 kg/m3. Therefore, it can be concluded that when the fiber content is 1.0 kg/m3 and the fiber length is 18 mm, the concrete exhibits the best impermeability performance.

3.4.2. Rapid Chloride Ion Permeability Coefficient Test

The chloride ion diffusion coefficient is an essential parameter for evaluating the impermeability of concrete. A lower diffusion coefficient indicates stronger resistance to chloride ions, meaning better impermeability of the concrete. As shown in Figure 7, the chloride ion diffusion coefficient of basalt fiber-reinforced concrete is lower than that of the reference concrete, indicating that the addition of fibers enhances the impermeability of the concrete.
The chloride ion migration coefficient of the reference concrete is 11.2 × 10−12 m2/s. The groups B1.0–6, B1.0–12, and B1.0–18 show reductions of 67.86%, 76.78%, and 83.04% compared to the B0 group when the fiber content is fixed, for example, at 1.0 kg/m3. The diffusion coefficient of basalt fiber concrete decreases as the fiber length increases, with the lowest electric flux observed when the fiber length is 18 mm. The groups B0.5–6, B1.0–6, and B1.5–6 show reductions of 47.32%, 67.86%, and 27.68% compared to the B0 group when the fiber length is fixed at 6 mm. The diffusion coefficient of basalt fiber concrete reaches its lowest point when the fiber content reaches 1.0 kg/m3. Therefore, the data variations measured by the RCM test are consistent with the electric flux test, showing that the optimal impermeability is achieved when the fiber content is 1.0 kg/m3 and the fiber length is 18 mm.
Microcracks inevitably exist between the sand, aggregate, and binder in concrete. These cracks, which are commonly found in concrete specimens, significantly increase the water permeability and reduce the impermeability. By adding fibers to the concrete, cracks can be effectively controlled. This is because small cracks that form early will eventually encounter the uniformly distributed basalt fibers in the concrete. The fibers generate a restraining force at both ends of the cracks, significantly preventing the crack from widening, reducing porosity, and thereby enhancing the impermeability of the concrete. However, it may result in an imbalance between the fibers and the cement paste when the fiber content is too high, causing the fibers to be distributed unevenly or to form clumps, which would hinder the reduction of internal voids and negatively affect the impermeability of the concrete. Therefore, when using basalt fibers to enhance the impermeability of concrete, it is essential to control the fiber content to avoid a reduction in impermeability caused by excessive fiber incorporation.

3.4.3. Function Fitting

To investigate the relationship between two different indicators used to measure the impermeability of concrete in the permeability test, nine experimental groups were designed based on two variables: basalt fiber content and fiber length, as specified in the mix design. Each group’s measured electrical flux and chloride ion migration coefficient were plotted as scatter plots, and a function fitting was performed on the data. The fitted curve is shown in Figure 8.
The electric flux and chloride ion migration coefficient exhibit the same trend of variation under identical fiber length and content, and there is a nonlinear relationship curve between the two. Ignoring errors caused by various influencing factors in the data, the fitting equation is the following:
E = 72.67 D 0.474
In this equation, E represents the electric flux, and D represents the chloride ion migration coefficient. This equation indicates that when all other variables are held constant, a nonlinear transformation can be made between the electric flux and the chloride ion migration coefficient. Using this fitted equation, it is possible to directly obtain one parameter that measures the impermeability of concrete when the other parameter is known. To some extent, this also helps verify the experimental data’s accuracy, reduce errors, and improve the precision of the test, thereby providing a reference for future experimental research on the impermeability performance of basalt fiber-reinforced concrete.

3.5. SEM Images Microstructure Analysis

SEM images can display the internal distribution of the microstructure of concrete and the fibers, allowing for a deeper analysis of the impact of basalt fiber incorporation on the concrete. Scanning electron microscopy (SEM) experiments were conducted on samples of the reference concrete and concrete specimens incorporating basalt fibers, regulus 8100 scanning electron microscope produced by Hitachi Scientific Instruments (Beijing) Co., Ltd. in Beijing, China is used. And the resulting SEM images are shown in Figure 9.
Figure 9a shows the reference concrete without basalt fiber. At this stage, the hydration degree is limited, with only a small amount of gel-like material and large voids and cracks within the structure. The presence of structural cracks and matrix micro-cracks increases the permeability of the concrete, allowing harmful substances from the external environment to enter the concrete matrix through the pathways formed by cracks, with water or air serving as the medium. The looser the internal structure of the concrete, the more easily external substances can penetrate the matrix. Moreover, many concrete structures are currently built in environments with high humidity, freeze–thaw cycles, and high corrosion, which, over time, exacerbate the damage to concrete buildings, reducing their service life and posing a threat to societal safety.
After the incorporation of basalt fiber, Figure 9b shows the ends of the basalt fibers passing through and filling the internal voids, tightly wrapping around the cement matrix, thereby reducing the number of pores. Additionally, a large amount of C-S-H gel and C-A-S-H gel adheres to the surface of the fibers and inside the concrete matrix. As hydration products of cement-based materials, these gels are generated through free water adsorbed on the fiber surface via hydration reactions. The fly ash spheres have become uneven, indicating that they have participated in the hydration reaction. The fly ash and silica fume waste promote the progress of secondary hydration reactions in the cementitious material, resulting in the formation of more C-A-S-H and C-S-H gel products, which enhance the density of the concrete matrix and improve the macro-performance of the concrete [39,40]. Furthermore, as the density increases, the pores and cracks in the cement matrix decrease, reducing the channels through which external substances can penetrate the matrix. The improved impermeability consequently enhances the concrete’s resistance to external corrosive substances, thereby extending the service life of concrete structures.
With a slight increase in fiber content, as shown in Figure 9c,d, the internal structure of the concrete becomes denser, and the overall integrity improves. However, the number of pores inside the concrete matrix increases when the fibers aggregate into clusters, thus weakening the integrity of the concrete. Additionally, it can be observed that the diameter of the fiber tip is smaller than the diameter of the part connecting the fiber to the concrete matrix. This is caused by the external tensile stress applied to the fiber in the concrete specimen. During the failure of the specimen, the fiber is stretched, which offsets part of the stress and eventually leads to fiber breakage. This demonstrates the synergistic effect between the fibers and the concrete matrix and confirms that the incorporation of fibers influences the mechanical properties of the concrete. As a result, basalt fiber concrete exhibits superior mechanical properties and impermeability compared to the reference concrete.

4. Conclusions

This study analyzes the effects of basalt fiber on the mechanical and impermeability properties of concrete by incorporating basalt fibers of different lengths and dosages. The specific conclusions of the study are as follows:
(1)
Incorporating basalt fibers improves the compressive strength of concrete. The maximum enhancement in compressive strength occurs when the fiber length is 18 mm and the dosage is 1.5 kg/m3. In this case, the 28-day compressive strength of concrete increased by 18.94% compared to the control group without fibers.
(2)
Basalt fibers with a length of 18 mm show better improvement in concrete tensile strength than fibers with 6 mm and 12 mm lengths. The tensile strength of concrete shows the most significant increase, rising by 37.43% compared to the control group when the fiber length is 18 mm and the dosage is 1.0 kg/m3.
(3)
Concrete flexural strength improves with the fiber length and dosage increase. The strength increase is as high as 28.72% compared to concrete without fibers when the fiber length is 18 mm and the fiber dosage is 1.5 kg/m3.
(4)
Concrete impermeability is enhanced after basalt fibers are incorporated. The electric flux and chloride ion diffusion coefficient are minimized when the fiber length is 18 mm and the dosage is 1.0 kg/m3. Smaller values of these parameters indicate stronger resistance of concrete to the penetration of water and ions, which results in better impermeability of fiber-reinforced concrete.
(5)
A nonlinear relationship exists between the electric flux measured by the electric flux method and the chloride ion diffusion coefficient calculated by the rapid chloride ion diffusion coefficient method. The fitted equation is: E = 72.67 D 0.474 .
(6)
Scanning electron microscopy (SEM) results show that after the incorporation of basalt fibers, the number of internal pores and cracks in the cement matrix decreases. Fly ash and silica fume waste promote the secondary hydration reaction process in the cementitious material, increasing gel products, improving the density of the concrete matrix, reducing the channels through which external substances can enter, and enhancing impermeability. The fibers in the concrete fracture surface are evenly distributed, resisting external tensile forces and effectively dissipating some of the energy, thereby improving the mechanical properties of the concrete.

Author Contributions

Conceptualization, Y.L. (Yishan Li) and Y.L. (Yan Liu); methodology, Y.L. (Yishan Li); validation, Y.L. (Yishan Li); formal analysis, Y.L. (Yishan Li); investigation, Y.L. (Yan Liu); resources, Y.L. (Yan Liu); data curation, Y.L. (Yishan Li); writing—original draft preparation, Y.L. (Yishan Li); writing—review and editing, Y.L. (Yishan Li), Y.L. (Yan Liu) and W.Z.; visualization, Y.L. (Yishan Li); supervision, Y.L. (Yan Liu) and W.Z.; project administration, Y.L. (Yan Liu); funding acquisition, W.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Natural Science Foundation of Hebei Province in China (E2024204008), the High-level Introduced Talent Research Project of Hebei Agricultural University of Chinese Universities (YJ2024007), and the Research project of Education Department of Hebei Province in China (KY2024002).

Data Availability Statement

Data is contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Minerals 15 00348 g001
Figure 1. Basalt fiber: (a) 6 mm, (b) 12 mm, (c) 18 mm.
Figure 1. Basalt fiber: (a) 6 mm, (b) 12 mm, (c) 18 mm.
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Figure 2. Basalt fiber concrete impermeability test: (a) Test instrument, (b) Electric flux test, (c) RCM test.
Figure 2. Basalt fiber concrete impermeability test: (a) Test instrument, (b) Electric flux test, (c) RCM test.
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Figure 3. Compressive strength of basalt fiber-reinforced concrete: (a) 7 d, (b) 28 d.
Figure 3. Compressive strength of basalt fiber-reinforced concrete: (a) 7 d, (b) 28 d.
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Figure 4. Tensile strength of basalt fiber-reinforced concrete: (a) 7 d, (b) 28 d.
Figure 4. Tensile strength of basalt fiber-reinforced concrete: (a) 7 d, (b) 28 d.
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Figure 5. Flexural tensile strength of basalt fiber-reinforced concrete: (a) 7 d, (b) 28 d.
Figure 5. Flexural tensile strength of basalt fiber-reinforced concrete: (a) 7 d, (b) 28 d.
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Figure 6. Electrical flux of basalt fiber-reinforced concrete.
Figure 6. Electrical flux of basalt fiber-reinforced concrete.
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Figure 7. Chloride ion migration coefficient of basalt fiber-reinforced concrete.
Figure 7. Chloride ion migration coefficient of basalt fiber-reinforced concrete.
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Figure 8. Fitting curve of electric flux and chloride ion migration coefficient.
Figure 8. Fitting curve of electric flux and chloride ion migration coefficient.
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Figure 9. The microstructure of fiber-reinforced concrete in 28 d. (a) Reference concrete. (b) 1.0 kg/m3 basalt fiber-reinforced concrete. (c) 0.5 kg/m3 basalt fiber-reinforced concrete. (d) 1.5 kg/m3 basalt fiber-reinforced concrete.
Figure 9. The microstructure of fiber-reinforced concrete in 28 d. (a) Reference concrete. (b) 1.0 kg/m3 basalt fiber-reinforced concrete. (c) 0.5 kg/m3 basalt fiber-reinforced concrete. (d) 1.5 kg/m3 basalt fiber-reinforced concrete.
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Table 1. Research status of the optimum proportion of basalt fiber.
Table 1. Research status of the optimum proportion of basalt fiber.
ScholarTestFiber LengthFiber ContentTime
Jiang, C. [27]tensile mechanical properties12 mm0.30%2014
Pehlivanh, Z.O. [28]compressive, flexural8 mm0.30%2015
Katkhuda, H. [29]compressive, splitting tensile, flexural18 mm0.30%2017
El-Gelani, A.M. [30]residual flexural stress/0.20%2018
Wang, X.Z. [31]mechanical property12 mm0.10%–0.50%2019
Zhou, H. [14]mechanical property12 mm0.40%2020
Yang, L. [32]compressive/0.26%2021
Yu, H. [33]anti-abrasion property/0.20%2022
Xu, Z.N. [34]compressive, splitting tensile12 mm0.10%2024
Wang, G. [35]mechanical property/0.50%2025
Table 2. Technical index of basalt fiber.
Table 2. Technical index of basalt fiber.
Testing ItemsDetection Result
main chemical componentsSiO2 Al2O3 CaCO3 MgO Fe2O3
fiber diameter (μm)17.00
proportion (g/cm3)2.80~3.30
tensile strength (N/tex)0.41
elastic modulus (GPa)100.00
Table 3. The main chemical composition of cementitious materials (mass fraction/%).
Table 3. The main chemical composition of cementitious materials (mass fraction/%).
MaterialsSiO2CaOAl2O3Fe2O3MgOSO3K2OTiO2
Cement18.3259.744.043.328.903.820.920.30
Fly ash50.6813.2823.206.454.361.320.240.47
Silica fume98.100.520.460.320.280.31--
Table 4. Coarse aggregate screening results.
Table 4. Coarse aggregate screening results.
Sieve Size/mm2519169.54.752.36
Pass rate/%99.9079.6057.3032.400.000.00
Table 5. Fine aggregate screening results.
Table 5. Fine aggregate screening results.
Sieve Size/mm4.752.361.180.600.300.150.075
Pass rate/%99.8090.6073.2065.4043.6024.202.60
Table 6. Basalt fiber-reinforced concrete reference mix proportion.
Table 6. Basalt fiber-reinforced concrete reference mix proportion.
Sample NO.Water
(kg/m3)		Cement
(kg/m3)		Coarse Aggregate (kg/m3)Fine Aggregate (kg/m3)Fly Ash
(kg/m3)		Silica Fume
(kg/m3)		Water Reducing Agent(kg/m3)Fiber Length (mm)Fiber Content (kg/m3)
B018532011956151554013.75/0
B0.5–618532011956151554013.7560.5
B0.5–1218532011956151554013.7512
B0.5–1818532011956151554013.7518
B1.0–618532011956151554013.7561.0
B1.0–1218532011956151554013.7512
B1.0–1818532011956151554013.7518
B1.5–618532011956151554013.7561.5
B1.5–1218532011956151554013.7512
B1.5–1818532011956151554013.7518
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Li, Y.; Liu, Y.; Zhang, W. Mechanical, Chloride Resistance, and Microstructural Properties of Basalt Fiber-Reinforced Fly Ash–Silica Fume Composite Concrete. Minerals 2025, 15, 348. https://doi.org/10.3390/min15040348

AMA Style

Li Y, Liu Y, Zhang W. Mechanical, Chloride Resistance, and Microstructural Properties of Basalt Fiber-Reinforced Fly Ash–Silica Fume Composite Concrete. Minerals. 2025; 15(4):348. https://doi.org/10.3390/min15040348

Chicago/Turabian Style

Li, Yishan, Yan Liu, and Wei Zhang. 2025. "Mechanical, Chloride Resistance, and Microstructural Properties of Basalt Fiber-Reinforced Fly Ash–Silica Fume Composite Concrete" Minerals 15, no. 4: 348. https://doi.org/10.3390/min15040348

APA Style

Li, Y., Liu, Y., & Zhang, W. (2025). Mechanical, Chloride Resistance, and Microstructural Properties of Basalt Fiber-Reinforced Fly Ash–Silica Fume Composite Concrete. Minerals, 15(4), 348. https://doi.org/10.3390/min15040348

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