Experimental study and numerical simulation of the effect of different fiber types on the basic mechanical properties of shotcrete

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This study selected steel fibers, glass fibers, and polypropylene fibers as research subjects. Through laboratory tests, numerical simulations, and field experiments, it investigated the enhancement laws of flexural and compressive strengths of concrete with different dosages of these three fibers. The study shows that: ( 1 ) After 28 days of curing, the flexural strength of concrete with steel fibers, glass fibers, and polypropylene fibers peaked at dosages of 2.0%, 1.5%, and 2.0%, respectively. Compared to plain concrete, the increases were 118.6%, 42.86%, and 138.6%, respectively. The compressive strength of concrete increased the most with dosages of 0.5%, 1.0%, and 2.0% for steel fibers, glass fibers, and polypropylene fibers, respectively, with increases of 2.13%, 10%, and 18.3%. It can be seen that the impact of these three fiber types on the compressive strength of concrete is significantly less than their impact on flexural strength. For enhancing flexural strength, the order is polypropylene fibers > steel fibers > glass fibers. Conversely, for compressive strength, the order is polypropylene fibers > glass fibers > steel fibers. ( 2 ) Based on ABAQUS numerical simulations, microscopic analysis indicates that fibers, due to their high yield capacity, enhance the connections between concrete elements, reduce stress concentration, and improve the mechanical properties of concrete. ( 3 ) For shotcrete, due to its high flexural strength requirements and the tendency of steel and glass fibers to agglomerate, polypropylene fibers at a dosage of 2.0% were preferred. ( 4 ) Using the optimal dosage, it was successfully applied to the wet shotcrete support of a return air shaft in a mine, where the maximum deformation of the roof and sides of the tunnel remained within allowable limits, meeting the normal usage requirements of the tunnel. The research findings can offer guidance and reference for the selection and further application of shotcrete. Physical sciences/Engineering Physical sciences/Engineering/Civil engineering Fiber Flexural strength Compressive strength Enhancement effect Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 Figure 23 Figure 24 Figure 25 Figure 26 Figure 27 1 Introduction Recently, shotcrete has been extensively promoted in tunnel support thanks to its capability for long-distance conveyance under high pressure and high support efficiency 1,2 . Furthermore, with continuous advancements in the study and development of concrete, it has become an indispensable material in modern construction due to its advantages, such as high-compressive strength, high density, low porosity, low cost and availability of raw materials 3–5 . However, compared to its compressive strength, its flexural strength is relatively low, and its bending toughness is relatively weak, making it susceptible to brittle failure 6,7 . This limitation significantly impacts concrete application as shotcrete material in geotechnical engineering fields such as tunnels, slopes, foundation pits, and mines, especially in situations requiring higher resistance to flexural strength and bending toughness 8 . However, in geotechnical engineering, challenges still exist regarding the choice of fiber type and its proportion in shotcrete, with improper selection likely leading to the spraying effect failing to meet the expected standards. Consequently, many scholars from around the world have carried out a significant amount of research on the performance of fiber-reinforced concrete. Xu et al. 9 examined the impact of size on the fracture energy of steel fiber-reinforced high-strength concrete, finding that adding steel fibers to high-strength concrete can, to some degree, effectively alleviate the impact of size effect on fracture energy. Grzymski et al. 10 developed a composite material of fiber-reinforced concrete (FRC) by adding various fibers to concrete to reduce its brittleness. Dvorkin et al. 11 proposed hybrid fiber reinforced concrete (HFRC) with steel and basalt fibers and investigated the mechanical properties of fiber reinforced fine grained concrete. Hu et al. 12 proposed introducing innovative alkali-resistant glass fibers (AR-GF) series products, namely Anti-Crak® HP (HP) and Anti Crak® HD (HD) mixed with FRS, to address the limitations of traditional fiber-reinforced shotcrete (FRS). The studies of the aforementioned scholars have found that the type, shape, and amount of fibers significantly influence the mechanical properties of concrete 13–16 . Different types of fibers have their applicability under specific engineering conditions; for example, in highly corrosive underground environments, it is crucial to select the appropriate anti-corrosion fibers while designing corrosion-resistant concrete. For sprayed concrete, the mechanisms and reinforcement effects of different types of fiber-reinforced concrete are not yet clear, often resulting in high rebound rates, early cracking, and spalling damage in the concrete. In light of this, the present paper, based on shotcrete, selects common steel fibers, glass fibers, and polypropylene fibers as research subjects. It systematically investigates the reinforcing effects of these three different types of fibers and their dosages on the bending and compressive strengths of concrete, aiming to recommend suitable fiber types and dosages for optimal application outcomes in shotcrete engineering. 2 Materials and methodologies 2.1 Raw Material The primary raw materials for the experiments include cement, stone, river sand, setting accelerator, and three different types of fibers: steel fibers, glass fibers, and polypropylene fibers. Figure 1 shows the three different types of fibers among the raw materials used in this experiment. 42.5 standard Portland cement was utilized as the basic cementing material for concrete; stones, serving as the coarse aggregate with a particle size of 5-8mm and spherical particles; natural river sand was used as fine aggregate for concrete, with a bulk density of 2560kg/m 3 and a fineness modulus of 2.71, to regulate the concrete's fineness; an alkali-free type of concrete setting accelerator was used to speed up the concrete's setting. The physical and mechanical properties of the steel fibers, glass fibers, and polypropylene fibers used in the experiment were shown in Tables 1 , 2 , and 3 , respectively. Combining raw materials based on their performance parameters, a series of experiments were conducted to investigate the effects of various fiber types on the bending and compressive strengths of concrete. Table 1 Performance parameters of steel fiber Length/ (mm) Diameter/ (mm) Density/ (g·cm − 3 ) Aspect ratio tensile strength /MPa 28 0.3 7.81 85 1500 Table 2 Performance parameters of glass fiber Length/ (mm) Diameter/ (µm) Density/(g·cm − 3 ) elongation at rupture/ (%) tensile strength /MPa 30 15 0.3 2.5 2000 Table 3 Performance parameters of polypropylene fiber Length/ (mm) Diameter/ (mm) Density/ (g·cm − 3 ) ignition temperature/ (℃) tensile strength /MPa 30 0.85 1.24 560 685 2.2 Design of the scheme To study the enhancement effect of different types of fibers on the mechanical properties of concrete, related experiments were conducted. Based on the common dosage of fibers in shotcrete projects, during the experiments, the dosages of the three types of fibers were set at five levels: 0, 0.5%, 1.0%, 1.5%, and 2.0%. Referring to previous experimental schemes, the specific experimental parameters are set as follows: the water-cement ratio is 0.6, the accelerator dosage is 1.2kg/m3 (applied externally), the cement dosage is 35% of the concrete mass, the river sand dosage is 45% of the concrete mass, and the stone dosage is 20% of the concrete mass. To reduce the randomness of the experimental results, this study provided three cubic specimens with the same dimensions (100mm×100mm×400mm) for each experimental group. The preparation and vibration of the specimens were conducted according to standards, using a forced mixer. After 5 minutes, the mixture was poured into molds, followed by manual vibration and smoothing. Vibration time was set at 60 seconds, guided by the slump test results. Subsequently, specimens were demolded after curing in a standard room for 3 days and 28 days, yielding the concrete samples. During the testing process, a 200kN electronic universal testing machine was used to conduct flexural and compressive strength tests on the concrete specimens. In terms of the electrometric and control system, the EDC100 model digital controller from DOLI, Germany, was used. As shown in Fig. 2 , during the test, the specimen's span was 300mm, using a three-point bending loading method with a loading rate of 0.2mm/min, and the deformation measurement accuracy was ± 1%. 3 Results and Discussion 3.1 Flexural strength of concrete with different fiber types After organizing, the following three sets of relationship figures (Fig. 3 , Fig. 4 , and Fig. 5 ) were obtained to analyze the impact of different types of fibers on the flexural mechanical properties of concrete. Figure 3 shows the flexural strength of concrete under different conditions of steel fiber dosage. Based on these results, the flexural strength of concrete exhibits a significant strengthening effect under different conditions of steel fiber dosage. With the increase in steel fiber dosage, the rate of increase in the flexural strength of steel fiber concrete exhibits a trend from rapid to slow. Specifically, with a steel fiber dosage of 1.0%, the flexural strength of concrete reached 11.7MPa and 13MPa after 3 and 28 days of curing, respectively, representing enhancement of 134% and 85.7%, respectively, compared to the flexural strength of reference concrete. When the steel fiber dosage is 2.0%, the flexural strengths at 3 days and 28 days increased to 13.9MPa and 15.3MPa, respectively, representing enhancements of 18.8% and 17.69% compared to concrete with 1.0% steel fiber dosage. Furthermore, with consistent steel fiber dosages, concrete cured for 28 days exhibits a flexural strength approximately 2 MPa greater than that of concrete cured for 3 days. Figure 4 shows the flexural strength of concrete under different glass fiber dosage conditions. Based on these results, the flexural strength of glass fiber concrete tends to increase and decrease as the glass fiber admixture increases. Specifically, when the glass fiber dosage ranges from 0–1.5%, the flexural strength of glass fiber-reinforced concrete gradually increases, with the growth rate remaining essentially constant. After 3 days and 28 days of curing, its flexural strength increased by 60% and 42.9%, respectively, compared to the reference concrete. When the glass fiber dosage varies between 1.5% and 2.0%, the flexural strength of glass fiber-reinforced concrete decreases. The flexural strength of concrete with 2.0% glass fiber dosage after 3 days and 28 days decreases by 6.25% and 7% compared to concrete with 1.5% glass fiber dosage. Thus, when the glass fiber dosage exceeds a certain value, the flexural strength of glass fiber-reinforced concrete continuously weakens. Figure 5 demonstrates the flexural strength of concrete across varying polypropylene fiber dosages. These results indicate a significant enhancement in concrete's flexural strength with varied polypropylene fiber dosages. The growth rate of the flexural strength in polypropylene fiber reinforced concrete initially increases slowly, then accelerates with higher polypropylene fiber dosages. Specifically, at polypropylene fiber dosages ranging from 0–1.0%, the flexural strength growth rate is relatively slow. After 3 and 28 days of curing, concrete with 1.0% polypropylene fiber dosage exhibited an 18% and 22.9% increase in flexural strength, respectively, compared to plain concrete. At polypropylene fiber dosages between 1.0% and 2.0%, the increase in flexural strength accelerates. After curing for 3 and 28 days, concrete with a 2.0% polypropylene fiber dosage showed a 147.5% and 94.2% increase in flexural strength, respectively, compared to the 1.0% dosage. 3.2 Compressive strength of concrete with different fiber types After organizing, the following three sets of relationship figures (Fig. 6 , Fig. 7 , and Fig. 8 ) were obtained to analyze the impact of different types of fibers on the compressive mechanical properties of concrete. Figure 6 demonstrates the compressive strength of concrete across various steel fiber dosages. These results reveal that with an increase in steel fiber dosage, the compressive strength of steel fiber-reinforced concrete initially rises, then falls. Specifically, for steel fiber dosages from 0–0.5%, compressive strength increases as the dosage rises. However, as dosages rise from 0.5–2.0%, there's a gradual decline in compressive strength. At 3 and 28 days, concrete with 0.5% steel fiber dosage showed a 2.5% and 2.13% increase in compressive strength, respectively, over reference concrete. However, concrete with 1.0%, 1.5%, and 2.0% steel fiber dosages demonstrated a decline in compressive strength compared to reference concrete at both 3 and 28 days. Additionally, steel fibers' impact on concrete's compressive strength is less significant compared to their effect on flexural strength. Figure 7 demonstrates the compressive strength of concrete across various glass fiber dosages. These findings indicate that the compressive strength of glass fiber-reinforced concrete first increases and then decreases with rising glass fiber dosages. After 3 and 28 days of curing, 1.0% glass fiber-reinforced concrete exhibited increases in compressive strength of 14.1% and 10%, respectively, compared to reference concrete. However, beyond a 1.0% glass fiber dosage, compressive strength gradually declines with further increases. After 3 and 28 days of curing, 2.0% glass fiber-reinforced concrete showed 10.86% and 7.87% increases in compressive strength, respectively, over reference concrete. Thus, a 1.0% glass fiber dosage is identified as the optimal amount for enhancing concrete's compressive strength. Compared to their impact on flexural strength, glass fibers have a more limited effect on concrete's compressive strength. Figure 8 demonstrates the flexural strength of concrete under various polypropylene fiber dosage conditions. The results indicate that for polypropylene fiber-reinforced concrete, compressive strength initially decreases and subsequently increases as polypropylene fiber dosages rise. Specifically, compressive strength decreases with increasing polypropylene fiber dosages up to 1.0%. After 3 and 28 days, concrete with a 1.0% polypropylene fiber dosage showed a decrease in compressive strength of 10.1% and 7.23%, respectively, compared to reference concrete. As polypropylene fiber dosage increases from 1.0–2.0%, there's a corresponding increase in compressive strength. Concrete with a 2.0% polypropylene fiber dosage exhibited a 20.24% and 18.3% increase in compressive strength after 3 and 28 days, respectively, compared to reference concrete. Polypropylene fibers have a weaker effect on enhancing concrete's compressive strength compared to their impact on flexural strength. 3.3 Analysis of the comparative effect of different fiber reinforcement After summarizing and organizing the above six sets of relationship curves, the maximum increases in the mechanical properties of reference concrete by different types of fibers were determined. As shown in Fig. 9 , there are differences in the maximum enhancement effect of different types of fibers on the flexural strength of concrete and the specific enhancement effect of each type of fiber was shown as follows: From Fig. 3 , it can be observed that when the steel fiber dosage reaches 2.0%, the enhancement effect on the concrete's flexural strength is most significant, with the maximum increasing amplification during the 3 days and 28 days curing periods being 178% and 118.6%, respectively. From Fig. 4 , it is observed that when the glass fiber dosage reaches 1.5%, the enhancement in flexural strength of concrete is most significant, with the maximum increasing amplification during the 3 days and 28 days curing periods being 60% and 42.86%, respectively. From Fig. 5 , it can be observed that when the polypropylene fiber dosage reaches 2.0%, the enhancement in flexural strength of concrete is most significant, with the maximum increasing amplification during the 3 days and 28 days curing periods being 192% and 138.6%, respectively. In summary, the enhancement effect of polypropylene fibers is the most significant, followed by steel fibers, while the effect of glass fibers on improving the flexural strength of concrete is weaker. As shown in Fig. 10 , there are differences in the maximum increase of compressive strength of concrete among different types of fibers. The specific enhancement effects of each type of fiber are as follows: From Fig. 6 , it can be observed that when the steel fiber dosage is 0.5%, the enhancement effect on the concrete's compressive strength is most significant, with the maximum increases of 2.5% and 2.13% during the 3-day and 28-day curing periods, respectively. From Fig. 7 , it can be observed that when the glass fiber dosage is 1.0%, the enhancement effect on the concrete's compressive strength is most significant, with maximum increases of 14.1% and 10% during the 3-day and 28-day curing periods, respectively. From Fig. 8 , it can be observed that when the polypropylene fiber dosage is 2.0%, the enhancement effect on the concrete's compressive strength is most significant, with the maximum increases of 20.25% and 18.3% during the 3-day and 28-day curing periods, respectively. In summary, the enhancement effect of polypropylene fibers is the most significant, followed by glass fibers. In contrast, steel fibers have a relatively weaker effect on improving the compressive strength of concrete, exerting a smaller impact. Compared to the enhancement effect of these three types of fibers on the flexural strength of concrete, their effect on improving the compressive strength of concrete is relatively limited. 4. Damage characteristics numerical simulation The study indicates that after 28 days of curing, the compressive strength of concrete reaches its maximum when the amounts of steel fiber, glass fiber, and polypropylene fiber are 0.5%, 1.0%, and 2.0%, respectively. The flexural strength of concrete with steel fiber, glass fiber, and polypropylene fiber reaches its peak at 2.0%, 1.5%, and 2.0% content, respectively. This study uses the ABAQUS finite element analysis method to investigate the damage analysis of fiber-reinforced concrete using the optimal content of the aforementioned fiber types. 4.1 Construction of the fiber-reinforced concrete model This study selects Python for secondary development to generate microscopic models of fiber-reinforced concrete for related experiments. The models studied in this paper are cubes of 100mm×100mm×100mm and rectangular prisms of 100mm×100mm×400mm. Then, fibers were inserted into the concrete matrix models to form the meso-scale fiber-reinforced concrete models. The interaction between fibers and concrete was modeled using ABAQUS's built-in embedded contact relationships, as shown in Figs. 11 and 12. ABAQUS incorporates a concrete plastic damage model, which introduces the concept of damage to better describe the mechanical characteristics of concrete under loading conditions. The parameters of the plastic damage model were uniformly processed according to the constitutive relationships of concrete specified in the GB50010-2010 code. Concrete was selected as C40, and material properties were assigned according to conventional parameters. The parameters of the concrete plastic damage model were selected according to the recommended values, as shown in Table 4 . Table 4 Parameters of the concrete plastic damage model expansive angle (°) eccentricity f b0 / f c0 K viscoelastic parameters 30 0.1 1.16 0.6667 0.0005 4.2 Analysis of simulation results 4.2.1 Validation of the numerical simulation's rationality By comparing the data (Table 5 ), the numerical simulation data of the model show little difference from the experimental data, with errors within an acceptable range. Thus, the ABAQUS numerical simulation presented in this study was deemed reasonable and feasible. Table 5 Comparison of simulation data and experimental data Category experimental data simulation data errors compressive test/MPa flexural test/MPa compressive test/MPa flexural test/MPa compressive test/MPa flexural test/MPa Steel fiber concrete 41.8 13.8 40.3 12.3 1.5 1.5 Glass fiber concrete 47.4 8.1 44.1 9.6 3.3 1.5 Polypropylene fiber concrete 49.1 14.8 42.5 13.7 6.6 1.1 4.2.2 The effect of different types of fibers on the compressive strength of concrete Figure 13 shows the displacement cloud diagram of concrete with different types of fibers. Figure 14 displays the maximum principal stress cloud diagram of concrete with different types of fibers. Figure 15 exhibits the compression damage cloud diagram of concrete with different types of fibers. Figure 16 illustrates the equivalent plastic strain cloud diagram of concrete with different types of fibers. Figure 17 shows the stress cloud diagram of different types of fibers in concrete. Figure 18 depicts the displacement cloud diagram of different types of fibers in concrete. From Fig. 13 significant displacement can be observed on the load-applied side of the concrete, gradually propagating downward. The displacement cloud diagram of plain concrete shows a relatively regular distribution. In contrast, fibers in fiber-reinforced concrete causes changes in the distribution, making it more uniform than plain concrete. Figures 14 , 15 , and 16 indicate that under uniaxial compression, the failure pattern of concrete specimens generally appears as an "X" shape. The surface damage of the concrete specimens suggests that adding fibers significantly reduces the degree of concrete damage. Figures 17 and 18 illustrate the stress-strain contour maps and displacement cloud diagrams of concrete with different types of fibers. Adding fibers enhances the connection between concrete elements, helps distribute stress concentration, and effectively improves the concrete's overall strength. The comparison shows that glass fibres perform best in enhancing concrete's resistance to deformation, reducing stress concentration, and minimizing compression damage. Polypropylene fibers come second, although performing well in all aspects, their overall effect is slightly inferior to glass fibers, while the enhancement effect of steel fibers is relatively weak. Table 5 shows that compared with plain concrete, the enhancement effect on the compressive performance of concrete is not significant. 4.2.3 The effect of different types of fibers on the flexural strength of concrete Figure 19 shows the tensile damage cloud diagram of concrete with different types of fibers. Figure 20 shows the displacement cloud diagram of different types of fibers in concrete. Figure 21 shows the displacement cloud diagram of different types of fibers in concrete. Figure 22 shows the variation of tensile damage in concrete elements. Figure 19 shows the tensile damage cloud diagram of concrete with different types of fibers at optimal dosage conditions. The concrete elements at the center of the lower part of the concrete were subjected to tensile stress and initially fail, progressively causing cracks to propagate upward, eventually leading to overall structural fracture. The contour maps show that the tensile damage distribution in fiber-reinforced concrete is smaller than in plain concrete, resulting in relatively smaller cracks and higher flexural strength. Figures 20 and 21 present the stress-strain contour maps of different types of fibers. It can be seen from the figures that the fibers in the middle part have the largest stress-strain, bearing a significant portion of the stress of the concrete elements, effectively enhancing the structure's flexural capacity. To further investigate the flexural capacity of concrete with different types of fibers, a unit in the lower part of the structure that fails first is selected for field variable output, showing the variation in tensile damage of the unit, as illustrated in Fig. 22 . From the figure, it is apparent that the plain concrete unit quickly fails and loses its function under applied load. In contrast, the fiber-reinforced concrete, due to the pull of the fibers which bear part of the stress, delays the failure of the concrete unit. It can be observed that polypropylene fibers exhibit the best load-bearing capacity. From the above analysis, it can be concluded that polypropylene fibers show the best enhancement effect in improving tensile performance and dispersing stress in concrete, followed by steel fibers. Glass fibers have a weaker enhancement effect but are still better than unreinforced plain concrete. As shown in Table 5 , compared to the compressive strength of fiber-reinforced concrete, the flexural performance was significantly improved due to the good yielding capability of the fibers, markedly enhancing the flexural mechanical properties of the concrete, thus the enhancement effect on the flexural capacity of the concrete is evident. 5 Description of reinforcement mechanisms for different types of fibers and recommendations for shotcrete 5.1 Description of the mechanisms of concrete reinforcement with different types of fibers 5.1.1 Description of steel fiber reinforcement mechanism In terms of improving the flexural strength of concrete with steel fibers, the presence of micro-fracture inside the concrete must be considered, as shown in Fig. 23(a). Under the condition of externally applied loads, stress concentration often occurs at the tips of these voids, leading to the expansion of the voids and ultimately causing concrete failure. Steel fibers act as void-bridging materials in concrete. They can mitigate the aforementioned issues, helping to reduce the stress concentration effect at the void tips, as shown in Fig. 23(b). This distributes the stress to the uncracked portions of the concrete, thereby significantly enhancing the concrete's flexural strength. In terms of compressive strength, the addition of steel fibers plays a significant role, but the amount added should be reasonable. When the dosage of steel fibers is low, it can partially suppress the lateral expansion deformation of the concrete matrix, thereby increasing the concrete's compressive strength. However, when the dosage of steel fibers is too high, it becomes difficult to distribute them evenly within the concrete matrix, leading to significant clustering, which creates weak areas in the concrete. These weak areas are essentially equivalent to internal defects in the concrete and may become the starting point for the failure of steel fiber-reinforced concrete. Therefore, it is necessary to control the amount of steel fibers added to avoid an excess that could reduce the concrete's compressive strength. 5.1.2 Description of glass fiber reinforcement mechanism In terms of the flexural strength of glass fiber reinforced concrete, as shown in Figs. 24(a) and (b), introducing glass fibers distributed in three-dimensional space into concrete can effectively share part of the stress on the concrete, reduce the load that the concrete itself needs to bear, thereby effectively inhibiting the expansion of cracks in the concrete, and further enhancing the concrete's flexural strength. However, once the dosage of glass fibers reaches a certain level, the fibers may clump together within the concrete, leading to uneven distribution of the fibers, as shown in Fig. 24(c). This uneven distribution can lead to uneven stress distribution in the glass fiber-reinforced concrete, causing stress concentration in localized areas, which ultimately results in these areas fracturing first. Therefore, when the dosage of glass fibers exceeds a certain threshold, the flexural strength of glass fiber-reinforced concrete may decrease; in terms of enhancing compressive strength, the mechanism is similar to that of increasing flexural strength. 5.1.3 Description of polypropylene fiber reinforcement mechanism In terms of the flexural strength of polypropylene fiber reinforced concrete, as demonstrated in Figs. 25(a) and (b), when the dosage of polypropylene fibers is too low, the intercrossing and entanglement of polypropylene fibers in the concrete can lead to clumping phenomena, resulting in internal defects within the concrete. However, once the dosage of polypropylene fibers exceeds a certain value, an approximate three-dimensional mesh structure can be formed within the concrete matrix, significantly improving the matrix's flexural strength, as shown in Fig. 25(c). In terms of enhancing compressive strength, initially, a small dosage of fibers in the concrete matrix absorbs the cement slurry, thereby reducing the dosage of cementitious material in the concrete and leading to a decrease in the concrete's compressive strength. Moreover, in the initial stages, the quantity of polypropylene fibers needs to be increased to form an effective three-dimensional network structure, limiting the enhancement effect on concrete strength and thus reducing the concrete's compressive strength. Once the dosage of polypropylene fibers reaches a certain level, a complex three-dimensional network structure can be formed, significantly enhancing the compressive strength of the concrete. 5.2 Recommendations for use of shotcrete Steel, glass, and polypropylene fibers are common materials for reinforcing concrete, effectively improving its crack, abrasion, and impact resistance. Based on the experimental analysis and enhancement mechanisms of the three types of fibers previously described, the following suggestions were made for shotcrete. In underground engineering, polypropylene fibers are usually more suitable as the raw fiber material for shotcrete as they have a more significant effect on enhancing concrete's mechanical properties than steel fibers and glass fibers. In practical use, it is necessary to determine the appropriate type and dosage of polypropylene fibers based on the specific requirements of different projects to meet the strength and durability requirements of the project. For routine shotcrete projects, it is recommended that the polypropylene fiber dosage be 2.0%. Additionally, it is crucial to ensure the uniform distribution of polypropylene fibers in concrete to ensure the uniformity of its performance. To achieve this goal, appropriate concrete mixing methods and process control measures can be employed to ensure the fibers are evenly distributed within the concrete, thus maximizing their reinforcing effect. 6 Monitoring of engineering applications Polypropylene concrete was used for the wet shotcrete support of a certain mine's return air-inclined shaft. Concrete formula: The water-cement ratio was selected as 0.6, with cement dosage at 35% of the concrete mass, river sand dosage at 45%, aggregate dosage at 20%, polypropylene dosage at 2.0%, rapid-setting admixture dosage at 1.2kg/m 3 , with the rapid-setting admixture being externally added, water-reducing agent dosage at 0.4%, and spray layer thickness at 50mm. The stress of the concrete spray layer was measured using an EBJ-C type concrete steel wire strain gauge, with a set of concrete strain gauges buried in both the roadway side and the roof at the observation station. The strain gauges were located in the middle of the concrete spray layer, and the results of the spray layer stress observations at the observation station were shown in Fig. 14 . The deformation of the roadway roof and both sides was observed using a roadway convergence deformation instrument, and Fig. 15 shows the curve of the surrounding rock deformation observations in the roadway. As shown in Fig. 26 , the stress measured at the monitoring points in the concrete spray layer is not significant, with the maximum stress in the spray layer at two side areas being slightly higher than that of the roadway roof spray layer. The maximum stress distribution for the roadway roof and side spray layers is 0.34MPa and 0.42MPa, respectively; the stress at the measuring points increases over time but eventually stabilizes. The growth rate of the spray layer stress gradually decreases and approaches zero, indicating that the lining is subject to minimal force and quickly becomes stable. As shown in Fig. 27 , during the observation period from 0 to 26 days, there was a gradual increase in the amount of deformation from the sinking of the roadway roof and convergence of the two sides; after day 26, the sinkage of the roadway roof and the convergence of the sides generally tended towards stability. The roadway roof's maximum displacement reached 56 mm, while the greatest convergence of the sides was 77 mm. Both the roadway roof's maximum deformation and the two sides' maximum convergence fell within allowable limits, ensuring the roadway's suitability for normal use. This demonstrates that the use of wet-sprayed polypropylene fiber concrete to support the return air-inclined shaft can effectively control the stability of the surrounding rock in the roadway. 7 Conclusions ( 1 ) Flexural strength in steel fiber-reinforced concrete gradually increases with addition, peaking at a 2.0% dosage, with glass fiber-reinforced concrete, flexural strength initially increases, then decreases, optimal at a 1.5% fiber dosage. Flexural strength in polypropylene fiber-reinforced concrete improves gradually with polypropylene fiber additions, achieving the maximum increase at a 2.0% dosage. The compressive strength of steel fiber reinforced concrete increases and then decreases, peaking at a dosage of 0.5%. Compressive strength in glass fiber-reinforced concrete rises initially, then falls, with the optimal increase at a 1.0% fiber dosage. Compressive strength in polypropylene fiber-reinforced concrete first decreases, then increases, achieving the maximum increase at a 2.0% fiber dosage. ( 2 ) The maximum enhancement of concrete's flexural strength by the three types of fibers is ranked as polypropylene fibers > steel fibers > glass fibers, and for compressive strength, the ranking is polypropylene fibers > glass fibers > steel fibers. It is important to note that, compared to their effect on flexural strength, the three types of fibers have a more limited effect on enhancing concrete's compressive strength. ( 3 ) The comparison of compressive and flexural test results with numerical simulation results verifies the correctness and validity of the numerical simulation. The fibers enhance the connection between concrete elements, helping to distribute part of the stress concentration and effectively improving the overall strength of the concrete. Especially during the flexural process, the strong yielding capacity greatly reduces the tensile damage to the concrete. ( 4 ) Based on the experimental analysis and reinforcement mechanisms described for the three types of fibers, the following recommendations are made for shotcrete. In underground engineering, polypropylene fibers are more suitable for shotcrete, as they can significantly improve the mechanical properties of concrete. In practical use, it is necessary to determine the appropriate type and dosage of polypropylene fibers based on the requirements of different projects to ensure their uniform distribution in the concrete. ( 5 ) Based on a wet shotcrete support project for a mine return air inclined shaft, during monitoring, stress and deformation gradually stabilized. The maximum stress distribution for the roadway roof and sides spray layer was 0.34MPa and 0.42MPa, respectively. The maximum displacement of the roadway roof was 56mm, and the maximum convergence of both sides was 77mm. Both the maximum deformation of the roadway roof and sides were within the allowable range, meeting the normal use of the roadway. This indicates that using wet spray polypropylene fiber concrete for supporting the return air inclined shaft effectively controls the stability of the surrounding rock of the roadway. Declarations Conflict of interest: The authors declare that they have no conflict of interest. Author Contribution Cheng-Yong Liu and Han-Qiu Wang participated in the writing and testing of the first draft of the paper. Xue-Feng Liu was involved in writing the first draft of the paper, revising the paper and proposing the methodology. Ming-Xue Niu and Ji-Fei Wu participate in numerical simulation calculations Acknowledgement The datasets used and/or analysed during the current study available from the corresponding author on reasonable request. Data Availability The datasets used and/or analysed during the current study available from the corresponding author on reasonable request. References Ahmed, L., & Ansell, A. Vibration vulnerability of shotcrete on tunnel walls during construction blasting. Tunnelling and Underground Space Technology 42, 105–111(2014). Chen, L., Sun, Z., Liu, G., Ma, G., & Liu, X. Spraying characteristics of mining wet shotcrete. Construction and Building Materials 316, 125888 (2022). Zhang, J. P., Liu, L. M., Zhu, Z. D., Zhang, F. T., & Cao, J. Z. Flexural fracture toughness and first-crack strength tests of steel fiber-silica fume concrete and its engineering applications. Strength of Materials 50, 166–175 (2018). Chen, L., Ma, G., Liu, G., & Liu, Z. Effect of pumping and spraying processes on the rheological properties and air content of wet-mix shotcrete with various admixtures. Construction and Building Materials 225, 311–323 (2019). Li, P., Zhou, Z., Chen, L., Liu, G., & Xiao, W. Research on dust suppression technology of shotcrete based on new spray equipment and process optimization. Advances in Civil Engineering (2019). Khan, M. U., Tahir, M. U., Emad, M. Z., Raza, M. A., & Saki, S. A. Investigating strength anisotropy of plain and steel fiber reinforced shotcrete. Mining, Metallurgy & Exploration 40(1), 291–303 (2023). He F, Biolzi L, Carvelli V. Effect of fiber hybridization on mechanical properties of concrete[J]. Materials and Structures 55(7): 195 (2022). Xu P, Ma J, Ding Y, et al. Influences of steel fiber content on size effect of the fracture energy of high-strength concrete[J]. KSCE Journal of Civil Engineering 25(3): 948–959 (2021). Xu H, Shao Z, Wang Z, et al. Experimental study on mechanical properties of fiber reinforced concrete: Effect of cellulose fiber, polyvinyl alcohol fiber, and polyolefin fiber [J]. Construction and Building Materials 261: 120610 (2020). Grzymski, F., Musiał, M., & Trapko, T. Mechanical properties of fibre reinforced concrete with recycled fibres. Construction and Building Materials 198, 323–331 (2019). Dvorkin, L., Bordiuzhenko, O., Tekle, B. H., & Ribakov, Y. A method for the design of concrete with combined steel and basalt fiber. Applied Sciences 11(19), 8850 (2021). Hu, Z., Wang, Q., Lv, H., Li, K., Zhang, J., & Ma, Y. Improved mechanical and macro-microscopic characteristics of shotcrete by incorporating hybrid alkali-resistant glass fibers. Construction and Building Materials 403, 133131 (2023). Bittner C M, Oettel V. Fiber Reinforced Concrete with Natural Plant Fibers—Investigations on the Application of Bamboo Fibers in Ultra-High Performance Concrete[J]. Sustainability 14(19): 12011 (2022). Islam M S, Ahmed S J U. Influence of jute fiber on concrete properties[J]. Construction and Building Materials 189: 768–776 (2018). Tuan B L A, Tesfamariam M G, Hwang C L, et al. Effect of fiber type and content on properties of high-strength fiber reinforced self-consolidating concrete[J]. Computers and Concrete, An International Journal 14(3): 299–313 (2014). Zhang D, Tan G Y, Tan K H. Combined effect of flax fibers and steel fibers on spalling resistance of ultra-high performance concrete at high temperature[J]. Cement and Concrete Composites 121: 104067 (2021). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 04 Nov, 2024 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 11 Sep, 2024 Reviews received at journal 07 Sep, 2024 Reviews received at journal 22 Aug, 2024 Reviewers agreed at journal 12 Aug, 2024 Reviewers agreed at journal 11 Aug, 2024 Reviewers agreed at journal 11 Aug, 2024 Reviewers invited by journal 29 May, 2024 Editor assigned by journal 29 May, 2024 Editor invited by journal 28 May, 2024 Submission checks completed at journal 25 May, 2024 First submitted to journal 22 May, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4464000","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":310211780,"identity":"d96f5564-c3f1-4de3-92e8-25b9eaf9b2be","order_by":0,"name":"Cheng-Yong Liu","email":"","orcid":"","institution":"China Coal Energy Research Institute Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Cheng-Yong","middleName":"","lastName":"Liu","suffix":""},{"id":310211781,"identity":"c8d2c592-3b86-43ab-ac57-b1786f702e87","order_by":1,"name":"Han-Qiu WANG","email":"","orcid":"","institution":"China Coal Energy Research Institute Co., 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Furthermore, with continuous advancements in the study and development of concrete, it has become an indispensable material in modern construction due to its advantages, such as high-compressive strength, high density, low porosity, low cost and availability of raw materials\u003csup\u003e3\u0026ndash;5\u003c/sup\u003e. However, compared to its compressive strength, its flexural strength is relatively low, and its bending toughness is relatively weak, making it susceptible to brittle failure\u003csup\u003e6,7\u003c/sup\u003e. This limitation significantly impacts concrete application as shotcrete material in geotechnical engineering fields such as tunnels, slopes, foundation pits, and mines, especially in situations requiring higher resistance to flexural strength and bending toughness\u003csup\u003e8\u003c/sup\u003e. However, in geotechnical engineering, challenges still exist regarding the choice of fiber type and its proportion in shotcrete, with improper selection likely leading to the spraying effect failing to meet the expected standards.\u003c/p\u003e \u003cp\u003eConsequently, many scholars from around the world have carried out a significant amount of research on the performance of fiber-reinforced concrete. Xu et al.\u003csup\u003e9\u003c/sup\u003e examined the impact of size on the fracture energy of steel fiber-reinforced high-strength concrete, finding that adding steel fibers to high-strength concrete can, to some degree, effectively alleviate the impact of size effect on fracture energy. Grzymski et al.\u003csup\u003e10\u003c/sup\u003e developed a composite material of fiber-reinforced concrete (FRC) by adding various fibers to concrete to reduce its brittleness. Dvorkin et al.\u003csup\u003e11\u003c/sup\u003e proposed hybrid fiber reinforced concrete (HFRC) with steel and basalt fibers and investigated the mechanical properties of fiber reinforced fine grained concrete. Hu et al.\u003csup\u003e12\u003c/sup\u003e proposed introducing innovative alkali-resistant glass fibers (AR-GF) series products, namely Anti-Crak\u0026reg; HP (HP) and Anti Crak\u0026reg; HD (HD) mixed with FRS, to address the limitations of traditional fiber-reinforced shotcrete (FRS).\u003c/p\u003e \u003cp\u003eThe studies of the aforementioned scholars have found that the type, shape, and amount of fibers significantly influence the mechanical properties of concrete\u003csup\u003e13\u0026ndash;16\u003c/sup\u003e. Different types of fibers have their applicability under specific engineering conditions; for example, in highly corrosive underground environments, it is crucial to select the appropriate anti-corrosion fibers while designing corrosion-resistant concrete. For sprayed concrete, the mechanisms and reinforcement effects of different types of fiber-reinforced concrete are not yet clear, often resulting in high rebound rates, early cracking, and spalling damage in the concrete. In light of this, the present paper, based on shotcrete, selects common steel fibers, glass fibers, and polypropylene fibers as research subjects. It systematically investigates the reinforcing effects of these three different types of fibers and their dosages on the bending and compressive strengths of concrete, aiming to recommend suitable fiber types and dosages for optimal application outcomes in shotcrete engineering.\u003c/p\u003e"},{"header":"2 Materials and methodologies","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Raw Material\u003c/h2\u003e\n \u003cp\u003eThe primary raw materials for the experiments include cement, stone, river sand, setting accelerator, and three different types of fibers: steel fibers, glass fibers, and polypropylene fibers. Figure\u0026nbsp;1 shows the three different types of fibers among the raw materials used in this experiment. 42.5 standard Portland cement was utilized as the basic cementing material for concrete; stones, serving as the coarse aggregate with a particle size of 5-8mm and spherical particles; natural river sand was used as fine aggregate for concrete, with a bulk density of 2560kg/m\u003csup\u003e3\u003c/sup\u003e and a fineness modulus of 2.71, to regulate the concrete\u0026apos;s fineness; an alkali-free type of concrete setting accelerator was used to speed up the concrete\u0026apos;s setting. The physical and mechanical properties of the steel fibers, glass fibers, and polypropylene fibers used in the experiment were shown in Tables \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e, and \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e, respectively. Combining raw materials based on their performance parameters, a series of experiments were conducted to investigate the effects of various fiber types on the bending and compressive strengths of concrete.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003ePerformance parameters of steel fiber\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eLength/ (mm)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDiameter/ (mm)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDensity/ (g\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAspect ratio\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003etensile strength /MPa\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1500\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003ePerformance parameters of glass fiber\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eLength/ (mm)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDiameter/ (\u0026micro;m)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDensity/(g\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eelongation at rupture/ (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003etensile strength /MPa\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003ePerformance parameters of polypropylene fiber\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eLength/ (mm)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDiameter/ (mm)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDensity/ (g\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eignition temperature/ (℃)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003etensile strength /MPa\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e560\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e685\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Design of the scheme\u003c/h2\u003e\n \u003cp\u003eTo study the enhancement effect of different types of fibers on the mechanical properties of concrete, related experiments were conducted. Based on the common dosage of fibers in shotcrete projects, during the experiments, the dosages of the three types of fibers were set at five levels: 0, 0.5%, 1.0%, 1.5%, and 2.0%. Referring to previous experimental schemes, the specific experimental parameters are set as follows: the water-cement ratio is 0.6, the accelerator dosage is 1.2kg/m3 (applied externally), the cement dosage is 35% of the concrete mass, the river sand dosage is 45% of the concrete mass, and the stone dosage is 20% of the concrete mass. To reduce the randomness of the experimental results, this study provided three cubic specimens with the same dimensions (100mm\u0026times;100mm\u0026times;400mm) for each experimental group. The preparation and vibration of the specimens were conducted according to standards, using a forced mixer. After 5 minutes, the mixture was poured into molds, followed by manual vibration and smoothing. Vibration time was set at 60 seconds, guided by the slump test results. Subsequently, specimens were demolded after curing in a standard room for 3 days and 28 days, yielding the concrete samples.\u003c/p\u003e\n \u003cp\u003eDuring the testing process, a 200kN electronic universal testing machine was used to conduct flexural and compressive strength tests on the concrete specimens. In terms of the electrometric and control system, the EDC100 model digital controller from DOLI, Germany, was used. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e, during the test, the specimen\u0026apos;s span was 300mm, using a three-point bending loading method with a loading rate of 0.2mm/min, and the deformation measurement accuracy was \u0026plusmn;\u0026thinsp;1%.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3 Results and Discussion","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Flexural strength of concrete with different fiber types\u003c/h2\u003e \u003cp\u003eAfter organizing, the following three sets of relationship figures (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e, and Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e) were obtained to analyze the impact of different types of fibers on the flexural mechanical properties of concrete.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the flexural strength of concrete under different conditions of steel fiber dosage. Based on these results, the flexural strength of concrete exhibits a significant strengthening effect under different conditions of steel fiber dosage. With the increase in steel fiber dosage, the rate of increase in the flexural strength of steel fiber concrete exhibits a trend from rapid to slow. Specifically, with a steel fiber dosage of 1.0%, the flexural strength of concrete reached 11.7MPa and 13MPa after 3 and 28 days of curing, respectively, representing enhancement of 134% and 85.7%, respectively, compared to the flexural strength of reference concrete. When the steel fiber dosage is 2.0%, the flexural strengths at 3 days and 28 days increased to 13.9MPa and 15.3MPa, respectively, representing enhancements of 18.8% and 17.69% compared to concrete with 1.0% steel fiber dosage. Furthermore, with consistent steel fiber dosages, concrete cured for 28 days exhibits a flexural strength approximately 2 MPa greater than that of concrete cured for 3 days.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the flexural strength of concrete under different glass fiber dosage conditions. Based on these results, the flexural strength of glass fiber concrete tends to increase and decrease as the glass fiber admixture increases. Specifically, when the glass fiber dosage ranges from 0\u0026ndash;1.5%, the flexural strength of glass fiber-reinforced concrete gradually increases, with the growth rate remaining essentially constant. After 3 days and 28 days of curing, its flexural strength increased by 60% and 42.9%, respectively, compared to the reference concrete. When the glass fiber dosage varies between 1.5% and 2.0%, the flexural strength of glass fiber-reinforced concrete decreases. The flexural strength of concrete with 2.0% glass fiber dosage after 3 days and 28 days decreases by 6.25% and 7% compared to concrete with 1.5% glass fiber dosage. Thus, when the glass fiber dosage exceeds a certain value, the flexural strength of glass fiber-reinforced concrete continuously weakens.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e demonstrates the flexural strength of concrete across varying polypropylene fiber dosages. These results indicate a significant enhancement in concrete's flexural strength with varied polypropylene fiber dosages. The growth rate of the flexural strength in polypropylene fiber reinforced concrete initially increases slowly, then accelerates with higher polypropylene fiber dosages. Specifically, at polypropylene fiber dosages ranging from 0\u0026ndash;1.0%, the flexural strength growth rate is relatively slow. After 3 and 28 days of curing, concrete with 1.0% polypropylene fiber dosage exhibited an 18% and 22.9% increase in flexural strength, respectively, compared to plain concrete. At polypropylene fiber dosages between 1.0% and 2.0%, the increase in flexural strength accelerates. After curing for 3 and 28 days, concrete with a 2.0% polypropylene fiber dosage showed a 147.5% and 94.2% increase in flexural strength, respectively, compared to the 1.0% dosage.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Compressive strength of concrete with different fiber types\u003c/h2\u003e \u003cp\u003eAfter organizing, the following three sets of relationship figures (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e, and Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e) were obtained to analyze the impact of different types of fibers on the compressive mechanical properties of concrete.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e demonstrates the compressive strength of concrete across various steel fiber dosages. These results reveal that with an increase in steel fiber dosage, the compressive strength of steel fiber-reinforced concrete initially rises, then falls. Specifically, for steel fiber dosages from 0\u0026ndash;0.5%, compressive strength increases as the dosage rises. However, as dosages rise from 0.5\u0026ndash;2.0%, there's a gradual decline in compressive strength. At 3 and 28 days, concrete with 0.5% steel fiber dosage showed a 2.5% and 2.13% increase in compressive strength, respectively, over reference concrete. However, concrete with 1.0%, 1.5%, and 2.0% steel fiber dosages demonstrated a decline in compressive strength compared to reference concrete at both 3 and 28 days. Additionally, steel fibers' impact on concrete's compressive strength is less significant compared to their effect on flexural strength.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e demonstrates the compressive strength of concrete across various glass fiber dosages. These findings indicate that the compressive strength of glass fiber-reinforced concrete first increases and then decreases with rising glass fiber dosages. After 3 and 28 days of curing, 1.0% glass fiber-reinforced concrete exhibited increases in compressive strength of 14.1% and 10%, respectively, compared to reference concrete. However, beyond a 1.0% glass fiber dosage, compressive strength gradually declines with further increases. After 3 and 28 days of curing, 2.0% glass fiber-reinforced concrete showed 10.86% and 7.87% increases in compressive strength, respectively, over reference concrete. Thus, a 1.0% glass fiber dosage is identified as the optimal amount for enhancing concrete's compressive strength. Compared to their impact on flexural strength, glass fibers have a more limited effect on concrete's compressive strength.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e demonstrates the flexural strength of concrete under various polypropylene fiber dosage conditions. The results indicate that for polypropylene fiber-reinforced concrete, compressive strength initially decreases and subsequently increases as polypropylene fiber dosages rise. Specifically, compressive strength decreases with increasing polypropylene fiber dosages up to 1.0%. After 3 and 28 days, concrete with a 1.0% polypropylene fiber dosage showed a decrease in compressive strength of 10.1% and 7.23%, respectively, compared to reference concrete. As polypropylene fiber dosage increases from 1.0\u0026ndash;2.0%, there's a corresponding increase in compressive strength. Concrete with a 2.0% polypropylene fiber dosage exhibited a 20.24% and 18.3% increase in compressive strength after 3 and 28 days, respectively, compared to reference concrete. Polypropylene fibers have a weaker effect on enhancing concrete's compressive strength compared to their impact on flexural strength.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Analysis of the comparative effect of different fiber reinforcement\u003c/h2\u003e \u003cp\u003eAfter summarizing and organizing the above six sets of relationship curves, the maximum increases in the mechanical properties of reference concrete by different types of fibers were determined.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e9\u003c/span\u003e, there are differences in the maximum enhancement effect of different types of fibers on the flexural strength of concrete and the specific enhancement effect of each type of fiber was shown as follows: From Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e, it can be observed that when the steel fiber dosage reaches 2.0%, the enhancement effect on the concrete's flexural strength is most significant, with the maximum increasing amplification during the 3 days and 28 days curing periods being 178% and 118.6%, respectively. From Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e, it is observed that when the glass fiber dosage reaches 1.5%, the enhancement in flexural strength of concrete is most significant, with the maximum increasing amplification during the 3 days and 28 days curing periods being 60% and 42.86%, respectively. From Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e, it can be observed that when the polypropylene fiber dosage reaches 2.0%, the enhancement in flexural strength of concrete is most significant, with the maximum increasing amplification during the 3 days and 28 days curing periods being 192% and 138.6%, respectively. In summary, the enhancement effect of polypropylene fibers is the most significant, followed by steel fibers, while the effect of glass fibers on improving the flexural strength of concrete is weaker.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e10\u003c/span\u003e, there are differences in the maximum increase of compressive strength of concrete among different types of fibers. The specific enhancement effects of each type of fiber are as follows: From Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e, it can be observed that when the steel fiber dosage is 0.5%, the enhancement effect on the concrete's compressive strength is most significant, with the maximum increases of 2.5% and 2.13% during the 3-day and 28-day curing periods, respectively. From Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e, it can be observed that when the glass fiber dosage is 1.0%, the enhancement effect on the concrete's compressive strength is most significant, with maximum increases of 14.1% and 10% during the 3-day and 28-day curing periods, respectively. From Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e, it can be observed that when the polypropylene fiber dosage is 2.0%, the enhancement effect on the concrete's compressive strength is most significant, with the maximum increases of 20.25% and 18.3% during the 3-day and 28-day curing periods, respectively. In summary, the enhancement effect of polypropylene fibers is the most significant, followed by glass fibers. In contrast, steel fibers have a relatively weaker effect on improving the compressive strength of concrete, exerting a smaller impact. Compared to the enhancement effect of these three types of fibers on the flexural strength of concrete, their effect on improving the compressive strength of concrete is relatively limited.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Damage characteristics numerical simulation","content":"\u003cp\u003eThe study indicates that after 28 days of curing, the compressive strength of concrete reaches its maximum when the amounts of steel fiber, glass fiber, and polypropylene fiber are 0.5%, 1.0%, and 2.0%, respectively. The flexural strength of concrete with steel fiber, glass fiber, and polypropylene fiber reaches its peak at 2.0%, 1.5%, and 2.0% content, respectively. This study uses the ABAQUS finite element analysis method to investigate the damage analysis of fiber-reinforced concrete using the optimal content of the aforementioned fiber types.\u003c/p\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e4.1 Construction of the fiber-reinforced concrete model\u003c/h2\u003e\n \u003cp\u003eThis study selects Python for secondary development to generate microscopic models of fiber-reinforced concrete for related experiments. The models studied in this paper are cubes of 100mm\u0026times;100mm\u0026times;100mm and rectangular prisms of 100mm\u0026times;100mm\u0026times;400mm. Then, fibers were inserted into the concrete matrix models to form the meso-scale fiber-reinforced concrete models. The interaction between fibers and concrete was modeled using ABAQUS\u0026apos;s built-in embedded contact relationships, as shown in Figs. \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e and 12.\u003c/p\u003e\n \u003cp\u003eABAQUS incorporates a concrete plastic damage model, which introduces the concept of damage to better describe the mechanical characteristics of concrete under loading conditions. The parameters of the plastic damage model were uniformly processed according to the constitutive relationships of concrete specified in the GB50010-2010 code.\u003c/p\u003e\n \u003cp\u003eConcrete was selected as C40, and material properties were assigned according to conventional parameters. The parameters of the concrete plastic damage model were selected according to the recommended values, as shown in Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eParameters of the concrete plastic damage model\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eexpansive angle (\u0026deg;)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eeccentricity\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003ef\u003c/em\u003e\u003csub\u003e\u003cem\u003eb0\u003c/em\u003e\u003c/sub\u003e/\u003cem\u003ef\u003c/em\u003e\u003csub\u003e\u003cem\u003ec0\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eK\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eviscoelastic parameters\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.6667\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0005\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e4.2 Analysis of simulation results\u003c/h2\u003e\n \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n \u003ch2\u003e4.2.1 Validation of the numerical simulation\u0026apos;s rationality\u003c/h2\u003e\n \u003cp\u003eBy comparing the data (Table \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e), the numerical simulation data of the model show little difference from the experimental data, with errors within an acceptable range. Thus, the ABAQUS numerical simulation presented in this study was deemed reasonable and feasible.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab5\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eComparison of simulation data and experimental data\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eCategory\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eexperimental data\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003esimulation data\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eerrors\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ecompressive test/MPa\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eflexural test/MPa\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ecompressive test/MPa\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eflexural test/MPa\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ecompressive test/MPa\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eflexural test/MPa\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSteel fiber concrete\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e41.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e40.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGlass fiber concrete\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e47.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e44.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolypropylene fiber concrete\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e49.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e42.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n \u003ch2\u003e4.2.2 The effect of different types of fibers on the compressive strength of concrete\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003e shows the displacement cloud diagram of concrete with different types of fibers. Figure \u003cspan class=\"InternalRef\"\u003e14\u003c/span\u003e displays the maximum principal stress cloud diagram of concrete with different types of fibers. Figure \u003cspan class=\"InternalRef\"\u003e15\u003c/span\u003e exhibits the compression damage cloud diagram of concrete with different types of fibers. Figure \u003cspan class=\"InternalRef\"\u003e16\u003c/span\u003e illustrates the equivalent plastic strain cloud diagram of concrete with different types of fibers. Figure \u003cspan class=\"InternalRef\"\u003e17\u003c/span\u003e shows the stress cloud diagram of different types of fibers in concrete. Figure 18 depicts the displacement cloud diagram of different types of fibers in concrete. From Fig. \u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003e significant displacement can be observed on the load-applied side of the concrete, gradually propagating downward. The displacement cloud diagram of plain concrete shows a relatively regular distribution. In contrast, fibers in fiber-reinforced concrete causes changes in the distribution, making it more uniform than plain concrete. Figures \u003cspan class=\"InternalRef\"\u003e14\u003c/span\u003e, \u003cspan class=\"InternalRef\"\u003e15\u003c/span\u003e, and \u003cspan class=\"InternalRef\"\u003e16\u003c/span\u003e indicate that under uniaxial compression, the failure pattern of concrete specimens generally appears as an \u0026quot;X\u0026quot; shape. The surface damage of the concrete specimens suggests that adding fibers significantly reduces the degree of concrete damage. Figures \u003cspan class=\"InternalRef\"\u003e17\u003c/span\u003e and 18 illustrate the stress-strain contour maps and displacement cloud diagrams of concrete with different types of fibers. Adding fibers enhances the connection between concrete elements, helps distribute stress concentration, and effectively improves the concrete\u0026apos;s overall strength. The comparison shows that glass fibres perform best in enhancing concrete\u0026apos;s resistance to deformation, reducing stress concentration, and minimizing compression damage. Polypropylene fibers come second, although performing well in all aspects, their overall effect is slightly inferior to glass fibers, while the enhancement effect of steel fibers is relatively weak. Table \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e shows that compared with plain concrete, the enhancement effect on the compressive performance of concrete is not significant.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\n \u003ch2\u003e4.2.3 The effect of different types of fibers on the flexural strength of concrete\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e19\u003c/span\u003e shows the tensile damage cloud diagram of concrete with different types of fibers. Figure \u003cspan class=\"InternalRef\"\u003e20\u003c/span\u003e shows the displacement cloud diagram of different types of fibers in concrete. Figure 21 shows the displacement cloud diagram of different types of fibers in concrete. Figure \u003cspan class=\"InternalRef\"\u003e22\u003c/span\u003e shows the variation of tensile damage in concrete elements. Figure \u003cspan class=\"InternalRef\"\u003e19\u003c/span\u003e shows the tensile damage cloud diagram of concrete with different types of fibers at optimal dosage conditions. The concrete elements at the center of the lower part of the concrete were subjected to tensile stress and initially fail, progressively causing cracks to propagate upward, eventually leading to overall structural fracture. The contour maps show that the tensile damage distribution in fiber-reinforced concrete is smaller than in plain concrete, resulting in relatively smaller cracks and higher flexural strength. Figures \u003cspan class=\"InternalRef\"\u003e20\u003c/span\u003e and 21 present the stress-strain contour maps of different types of fibers. It can be seen from the figures that the fibers in the middle part have the largest stress-strain, bearing a significant portion of the stress of the concrete elements, effectively enhancing the structure\u0026apos;s flexural capacity. To further investigate the flexural capacity of concrete with different types of fibers, a unit in the lower part of the structure that fails first is selected for field variable output, showing the variation in tensile damage of the unit, as illustrated in Fig. \u003cspan class=\"InternalRef\"\u003e22\u003c/span\u003e. From the figure, it is apparent that the plain concrete unit quickly fails and loses its function under applied load. In contrast, the fiber-reinforced concrete, due to the pull of the fibers which bear part of the stress, delays the failure of the concrete unit. It can be observed that polypropylene fibers exhibit the best load-bearing capacity. From the above analysis, it can be concluded that polypropylene fibers show the best enhancement effect in improving tensile performance and dispersing stress in concrete, followed by steel fibers. Glass fibers have a weaker enhancement effect but are still better than unreinforced plain concrete. As shown in Table \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e, compared to the compressive strength of fiber-reinforced concrete, the flexural performance was significantly improved due to the good yielding capability of the fibers, markedly enhancing the flexural mechanical properties of the concrete, thus the enhancement effect on the flexural capacity of the concrete is evident.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"5 Description of reinforcement mechanisms for different types of fibers and recommendations for shotcrete","content":"\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\n \u003ch2\u003e5.1 Description of the mechanisms of concrete reinforcement with different types of fibers\u003c/h2\u003e\n \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e\n \u003ch2\u003e5.1.1 Description of steel fiber reinforcement mechanism\u003c/h2\u003e\n \u003cp\u003eIn terms of improving the flexural strength of concrete with steel fibers, the presence of micro-fracture inside the concrete must be considered, as shown in Fig. 23(a). Under the condition of externally applied loads, stress concentration often occurs at the tips of these voids, leading to the expansion of the voids and ultimately causing concrete failure. Steel fibers act as void-bridging materials in concrete. They can mitigate the aforementioned issues, helping to reduce the stress concentration effect at the void tips, as shown in Fig. 23(b). This distributes the stress to the uncracked portions of the concrete, thereby significantly enhancing the concrete\u0026apos;s flexural strength. In terms of compressive strength, the addition of steel fibers plays a significant role, but the amount added should be reasonable. When the dosage of steel fibers is low, it can partially suppress the lateral expansion deformation of the concrete matrix, thereby increasing the concrete\u0026apos;s compressive strength. However, when the dosage of steel fibers is too high, it becomes difficult to distribute them evenly within the concrete matrix, leading to significant clustering, which creates weak areas in the concrete. These weak areas are essentially equivalent to internal defects in the concrete and may become the starting point for the failure of steel fiber-reinforced concrete. Therefore, it is necessary to control the amount of steel fibers added to avoid an excess that could reduce the concrete\u0026apos;s compressive strength.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e\n \u003ch2\u003e5.1.2 Description of glass fiber reinforcement mechanism\u003c/h2\u003e\n \u003cp\u003eIn terms of the flexural strength of glass fiber reinforced concrete, as shown in Figs. 24(a) and (b), introducing glass fibers distributed in three-dimensional space into concrete can effectively share part of the stress on the concrete, reduce the load that the concrete itself needs to bear, thereby effectively inhibiting the expansion of cracks in the concrete, and further enhancing the concrete\u0026apos;s flexural strength. However, once the dosage of glass fibers reaches a certain level, the fibers may clump together within the concrete, leading to uneven distribution of the fibers, as shown in Fig. 24(c). This uneven distribution can lead to uneven stress distribution in the glass fiber-reinforced concrete, causing stress concentration in localized areas, which ultimately results in these areas fracturing first. Therefore, when the dosage of glass fibers exceeds a certain threshold, the flexural strength of glass fiber-reinforced concrete may decrease; in terms of enhancing compressive strength, the mechanism is similar to that of increasing flexural strength.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec19\" class=\"Section3\"\u003e\n \u003ch2\u003e5.1.3 Description of polypropylene fiber reinforcement mechanism\u003c/h2\u003e\n \u003cp\u003eIn terms of the flexural strength of polypropylene fiber reinforced concrete, as demonstrated in Figs. 25(a) and (b), when the dosage of polypropylene fibers is too low, the intercrossing and entanglement of polypropylene fibers in the concrete can lead to clumping phenomena, resulting in internal defects within the concrete. However, once the dosage of polypropylene fibers exceeds a certain value, an approximate three-dimensional mesh structure can be formed within the concrete matrix, significantly improving the matrix\u0026apos;s flexural strength, as shown in Fig. 25(c). In terms of enhancing compressive strength, initially, a small dosage of fibers in the concrete matrix absorbs the cement slurry, thereby reducing the dosage of cementitious material in the concrete and leading to a decrease in the concrete\u0026apos;s compressive strength. Moreover, in the initial stages, the quantity of polypropylene fibers needs to be increased to form an effective three-dimensional network structure, limiting the enhancement effect on concrete strength and thus reducing the concrete\u0026apos;s compressive strength. Once the dosage of polypropylene fibers reaches a certain level, a complex three-dimensional network structure can be formed, significantly enhancing the compressive strength of the concrete.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec20\" class=\"Section2\"\u003e\n \u003ch2\u003e5.2 Recommendations for use of shotcrete\u003c/h2\u003e\n \u003cp\u003eSteel, glass, and polypropylene fibers are common materials for reinforcing concrete, effectively improving its crack, abrasion, and impact resistance. Based on the experimental analysis and enhancement mechanisms of the three types of fibers previously described, the following suggestions were made for shotcrete. In underground engineering, polypropylene fibers are usually more suitable as the raw fiber material for shotcrete as they have a more significant effect on enhancing concrete\u0026apos;s mechanical properties than steel fibers and glass fibers. In practical use, it is necessary to determine the appropriate type and dosage of polypropylene fibers based on the specific requirements of different projects to meet the strength and durability requirements of the project. For routine shotcrete projects, it is recommended that the polypropylene fiber dosage be 2.0%. Additionally, it is crucial to ensure the uniform distribution of polypropylene fibers in concrete to ensure the uniformity of its performance. To achieve this goal, appropriate concrete mixing methods and process control measures can be employed to ensure the fibers are evenly distributed within the concrete, thus maximizing their reinforcing effect.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"6 Monitoring of engineering applications","content":"\u003cp\u003ePolypropylene concrete was used for the wet shotcrete support of a certain mine's return air-inclined shaft. Concrete formula: The water-cement ratio was selected as 0.6, with cement dosage at 35% of the concrete mass, river sand dosage at 45%, aggregate dosage at 20%, polypropylene dosage at 2.0%, rapid-setting admixture dosage at 1.2kg/m\u003csup\u003e3\u003c/sup\u003e, with the rapid-setting admixture being externally added, water-reducing agent dosage at 0.4%, and spray layer thickness at 50mm.\u003c/p\u003e \u003cp\u003eThe stress of the concrete spray layer was measured using an EBJ-C type concrete steel wire strain gauge, with a set of concrete strain gauges buried in both the roadway side and the roof at the observation station. The strain gauges were located in the middle of the concrete spray layer, and the results of the spray layer stress observations at the observation station were shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e14\u003c/span\u003e. The deformation of the roadway roof and both sides was observed using a roadway convergence deformation instrument, and Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e15\u003c/span\u003e shows the curve of the surrounding rock deformation observations in the roadway.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig19\" class=\"InternalRef\"\u003e26\u003c/span\u003e, the stress measured at the monitoring points in the concrete spray layer is not significant, with the maximum stress in the spray layer at two side areas being slightly higher than that of the roadway roof spray layer. The maximum stress distribution for the roadway roof and side spray layers is 0.34MPa and 0.42MPa, respectively; the stress at the measuring points increases over time but eventually stabilizes. The growth rate of the spray layer stress gradually decreases and approaches zero, indicating that the lining is subject to minimal force and quickly becomes stable.\u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig20\" class=\"InternalRef\"\u003e27\u003c/span\u003e, during the observation period from 0 to 26 days, there was a gradual increase in the amount of deformation from the sinking of the roadway roof and convergence of the two sides; after day 26, the sinkage of the roadway roof and the convergence of the sides generally tended towards stability. The roadway roof's maximum displacement reached 56 mm, while the greatest convergence of the sides was 77 mm. Both the roadway roof's maximum deformation and the two sides' maximum convergence fell within allowable limits, ensuring the roadway's suitability for normal use. This demonstrates that the use of wet-sprayed polypropylene fiber concrete to support the return air-inclined shaft can effectively control the stability of the surrounding rock in the roadway.\u003c/p\u003e"},{"header":"7 Conclusions","content":"\u003cp\u003e(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) Flexural strength in steel fiber-reinforced concrete gradually increases with addition, peaking at a 2.0% dosage, with glass fiber-reinforced concrete, flexural strength initially increases, then decreases, optimal at a 1.5% fiber dosage. Flexural strength in polypropylene fiber-reinforced concrete improves gradually with polypropylene fiber additions, achieving the maximum increase at a 2.0% dosage. The compressive strength of steel fiber reinforced concrete increases and then decreases, peaking at a dosage of 0.5%. Compressive strength in glass fiber-reinforced concrete rises initially, then falls, with the optimal increase at a 1.0% fiber dosage. Compressive strength in polypropylene fiber-reinforced concrete first decreases, then increases, achieving the maximum increase at a 2.0% fiber dosage.\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) The maximum enhancement of concrete's flexural strength by the three types of fibers is ranked as polypropylene fibers\u0026thinsp;\u0026gt;\u0026thinsp;steel fibers\u0026thinsp;\u0026gt;\u0026thinsp;glass fibers, and for compressive strength, the ranking is polypropylene fibers\u0026thinsp;\u0026gt;\u0026thinsp;glass fibers\u0026thinsp;\u0026gt;\u0026thinsp;steel fibers. It is important to note that, compared to their effect on flexural strength, the three types of fibers have a more limited effect on enhancing concrete's compressive strength.\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) The comparison of compressive and flexural test results with numerical simulation results verifies the correctness and validity of the numerical simulation. The fibers enhance the connection between concrete elements, helping to distribute part of the stress concentration and effectively improving the overall strength of the concrete. Especially during the flexural process, the strong yielding capacity greatly reduces the tensile damage to the concrete.\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e) Based on the experimental analysis and reinforcement mechanisms described for the three types of fibers, the following recommendations are made for shotcrete. In underground engineering, polypropylene fibers are more suitable for shotcrete, as they can significantly improve the mechanical properties of concrete. In practical use, it is necessary to determine the appropriate type and dosage of polypropylene fibers based on the requirements of different projects to ensure their uniform distribution in the concrete.\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e) Based on a wet shotcrete support project for a mine return air inclined shaft, during monitoring, stress and deformation gradually stabilized. The maximum stress distribution for the roadway roof and sides spray layer was 0.34MPa and 0.42MPa, respectively. The maximum displacement of the roadway roof was 56mm, and the maximum convergence of both sides was 77mm. Both the maximum deformation of the roadway roof and sides were within the allowable range, meeting the normal use of the roadway. This indicates that using wet spray polypropylene fiber concrete for supporting the return air inclined shaft effectively controls the stability of the surrounding rock of the roadway.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003e\u003cstrong\u003eConflict of interest:\u003c/strong\u003e\u003c/h2\u003e\n\u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eCheng-Yong Liu and Han-Qiu Wang participated in the writing and testing of the first draft of the paper. Xue-Feng Liu was involved in writing the first draft of the paper, revising the paper and proposing the methodology. Ming-Xue Niu and Ji-Fei Wu participate in numerical simulation calculations\u003c/p\u003e\n\u003ch2\u003eAcknowledgement\u003c/h2\u003e\n\u003cp\u003eThe datasets used and/or analysed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003ch2\u003eData Availability\u003c/h2\u003e\n\u003cp\u003eThe datasets used and/or analysed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAhmed, L., \u0026amp; Ansell, A. Vibration vulnerability of shotcrete on tunnel walls during construction blasting. Tunnelling and Underground Space Technology 42, 105\u0026ndash;111(2014).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen, L., Sun, Z., Liu, G., Ma, G., \u0026amp; Liu, X. Spraying characteristics of mining wet shotcrete. Construction and Building Materials 316, 125888 (2022).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang, J. P., Liu, L. M., Zhu, Z. D., Zhang, F. T., \u0026amp; Cao, J. Z. Flexural fracture toughness and first-crack strength tests of steel fiber-silica fume concrete and its engineering applications. Strength of Materials 50, 166\u0026ndash;175 (2018).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen, L., Ma, G., Liu, G., \u0026amp; Liu, Z. Effect of pumping and spraying processes on the rheological properties and air content of wet-mix shotcrete with various admixtures. Construction and Building Materials 225, 311\u0026ndash;323 (2019).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi, P., Zhou, Z., Chen, L., Liu, G., \u0026amp; Xiao, W. Research on dust suppression technology of shotcrete based on new spray equipment and process optimization. Advances in Civil Engineering (2019).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKhan, M. U., Tahir, M. U., Emad, M. Z., Raza, M. A., \u0026amp; Saki, S. A. Investigating strength anisotropy of plain and steel fiber reinforced shotcrete. Mining, Metallurgy \u0026amp; Exploration 40(1), 291\u0026ndash;303 (2023).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHe F, Biolzi L, Carvelli V. Effect of fiber hybridization on mechanical properties of concrete[J]. Materials and Structures 55(7): 195 (2022).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXu P, Ma J, Ding Y, et al. Influences of steel fiber content on size effect of the fracture energy of high-strength concrete[J]. KSCE Journal of Civil Engineering 25(3): 948\u0026ndash;959 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXu H, Shao Z, Wang Z, et al. Experimental study on mechanical properties of fiber reinforced concrete: Effect of cellulose fiber, polyvinyl alcohol fiber, and polyolefin fiber [J]. Construction and Building Materials 261: 120610 (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGrzymski, F., Musiał, M., \u0026amp; Trapko, T. Mechanical properties of fibre reinforced concrete with recycled fibres. Construction and Building Materials 198, 323\u0026ndash;331 (2019).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDvorkin, L., Bordiuzhenko, O., Tekle, B. H., \u0026amp; Ribakov, Y. A method for the design of concrete with combined steel and basalt fiber. Applied Sciences 11(19), 8850 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHu, Z., Wang, Q., Lv, H., Li, K., Zhang, J., \u0026amp; Ma, Y. Improved mechanical and macro-microscopic characteristics of shotcrete by incorporating hybrid alkali-resistant glass fibers. Construction and Building Materials 403, 133131 (2023).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBittner C M, Oettel V. Fiber Reinforced Concrete with Natural Plant Fibers\u0026mdash;Investigations on the Application of Bamboo Fibers in Ultra-High Performance Concrete[J]. Sustainability 14(19): 12011 (2022).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIslam M S, Ahmed S J U. Influence of jute fiber on concrete properties[J]. Construction and Building Materials 189: 768\u0026ndash;776 (2018).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTuan B L A, Tesfamariam M G, Hwang C L, et al. Effect of fiber type and content on properties of high-strength fiber reinforced self-consolidating concrete[J]. Computers and Concrete, An International Journal 14(3): 299\u0026ndash;313 (2014).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang D, Tan G Y, Tan K H. Combined effect of flax fibers and steel fibers on spalling resistance of ultra-high performance concrete at high temperature[J]. Cement and Concrete Composites 121: 104067 (2021).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Fiber, Flexural strength, Compressive strength, Enhancement effect","lastPublishedDoi":"10.21203/rs.3.rs-4464000/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4464000/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe enhancement effects and mechanisms of different types of fibers on the basic mechanical properties of concrete were analyzed, aiming to guide the selection of suitable fiber types and dosages for grouting projects. This study selected steel fibers, glass fibers, and polypropylene fibers as research subjects. Through laboratory tests, numerical simulations, and field experiments, it investigated the enhancement laws of flexural and compressive strengths of concrete with different dosages of these three fibers. The study shows that: (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) After 28 days of curing, the flexural strength of concrete with steel fibers, glass fibers, and polypropylene fibers peaked at dosages of 2.0%, 1.5%, and 2.0%, respectively. Compared to plain concrete, the increases were 118.6%, 42.86%, and 138.6%, respectively. The compressive strength of concrete increased the most with dosages of 0.5%, 1.0%, and 2.0% for steel fibers, glass fibers, and polypropylene fibers, respectively, with increases of 2.13%, 10%, and 18.3%. It can be seen that the impact of these three fiber types on the compressive strength of concrete is significantly less than their impact on flexural strength. For enhancing flexural strength, the order is polypropylene fibers\u0026thinsp;\u0026gt;\u0026thinsp;steel fibers\u0026thinsp;\u0026gt;\u0026thinsp;glass fibers. Conversely, for compressive strength, the order is polypropylene fibers\u0026thinsp;\u0026gt;\u0026thinsp;glass fibers\u0026thinsp;\u0026gt;\u0026thinsp;steel fibers. (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) Based on ABAQUS numerical simulations, microscopic analysis indicates that fibers, due to their high yield capacity, enhance the connections between concrete elements, reduce stress concentration, and improve the mechanical properties of concrete. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) For shotcrete, due to its high flexural strength requirements and the tendency of steel and glass fibers to agglomerate, polypropylene fibers at a dosage of 2.0% were preferred. (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e) Using the optimal dosage, it was successfully applied to the wet shotcrete support of a return air shaft in a mine, where the maximum deformation of the roof and sides of the tunnel remained within allowable limits, meeting the normal usage requirements of the tunnel. The research findings can offer guidance and reference for the selection and further application of shotcrete.\u003c/p\u003e","manuscriptTitle":"Experimental study and numerical simulation of the effect of different fiber types on the basic mechanical properties of shotcrete","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-06 10:43:13","doi":"10.21203/rs.3.rs-4464000/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-09-11T05:40:16+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-09-07T19:04:53+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-08-22T13:11:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"258886679336129158068923286217605017635","date":"2024-08-12T19:20:35+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"301270058039020128105076856042705382846","date":"2024-08-11T07:36:40+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"145401247534467589622808345523841447714","date":"2024-08-11T07:29:32+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-05-30T01:04:42+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-05-30T00:53:47+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2024-05-28T13:40:19+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-05-25T04:46:31+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2024-05-23T03:51:46+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7a56c093-28ab-4c06-93ca-3e54e3e78b2b","owner":[],"postedDate":"June 6th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":32779934,"name":"Physical sciences/Engineering"},{"id":32779935,"name":"Physical sciences/Engineering/Civil engineering"}],"tags":[],"updatedAt":"2024-11-11T16:05:46+00:00","versionOfRecord":{"articleIdentity":"rs-4464000","link":"https://doi.org/10.1038/s41598-024-75927-8","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2024-11-04 15:57:46","publishedOnDateReadable":"November 4th, 2024"},"versionCreatedAt":"2024-06-06 10:43:13","video":"","vorDoi":"10.1038/s41598-024-75927-8","vorDoiUrl":"https://doi.org/10.1038/s41598-024-75927-8","workflowStages":[]},"version":"v1","identity":"rs-4464000","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4464000","identity":"rs-4464000","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}