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. 2024 Jun 12;9(25):26973–26982. doi: 10.1021/acsomega.3c10076

Compressive Properties of Basalt Fibers and Polypropylene Fiber-Reinforced Lightweight Concrete

Shengda Xu †, Kaiyue Yan †, Tao Jiang †, Ying Wang †, Shanshan Shi †, Wenge Li †,*, Yuantao Zhao †, Kai Sun †, Jinhong Yu §, Xinfeng Wu †,‡,*
PMCID: PMC11209689  PMID: 38947776

Abstract

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With the development of high-rise and large-scale modern structures, traditional concrete has become a design limitation due to its excessive dead weight. High-strength lightweight concrete is being emphasized. Lightweight concrete has low density and the characteristics of a brittle material. This is an important factor affecting the strength and ductility of the lightweight concrete. To improve these shortcomings and proffer solutions, a three-phase composite lightweight concrete was prepared using a combination of tumbling and molding methods. This paper investigates the various influencing factors such as the stacking volume fraction of GFR-EMS, the type of fiber, and the content and length of fiber in the matrix. Studies have shown that the addition of fibers significantly increases the compressive strength of the concrete. The compressive strength of concrete with a 12 mm basalt fiber (BF) (1.5%) admixture is 9.08 MPa, which is 62.43% higher than that of concrete without the fiber admixture. The compressive strength was increased by 27.53 and 21.88% compared to concrete containing 3 mm BF (1.5%) and 0.5% BF (12 mm), respectively. Fibers can fill the pore defects within the matrix. Mutually overlapping fibers easily form a network structure to improve the bond between the cement matrix and the aggregate particles. The compressive strength of lightweight concrete with the addition of BF was 16.71% higher than that with the addition of polypropylene fiber (PPF) with the same length and content of fibers. BF has been shown to be more effective in improving the mechanical properties of concrete. In this work, the compressive mechanism and optimum preparation parameters of a three-phase composite lightweight concrete were analyzed through compression tests. This provides some insights into the development of lightweight concrete.

1. Introduction

Concrete is the most widely used and largest material in civil engineering.1 Excessive self-weight of concrete is no longer suitable for the development of high-rise and large-scale modern structural design. Lightweight concrete2,3 is a low-density cementitious material with an apparent density of less than 1950 kg/m3, which has the advantages of light dead weight, thermal insulation, heat insulation, and sound insulation. Lightweight concrete can reduce its own constant load and improve the seismic response of the structure compared to that of conventional concrete. It has a broad application prospect.4,5

Lightweight concrete is mainly prepared from lightweight aggregates and cementitious materials.6,7 The sources of light aggregates can be classified as natural light aggregates (pumice,8 volcanic ash9), industrial wastes (expanded slag beads,10 fly ash ceramic granules11,12), and man-made light aggregates (ceramic pellets,13 shale pellets14). The filling of lightweight aggregates forms a porous structure within the lightweight concrete, reducing the density of the concrete. The reduction in density also brings about a decrease in compressive strength. The reduction in the density of concrete facilitates the development of taller buildings. However, the reduction of density needs to be balanced with the strength of the concrete. It is of good research value to make concrete have a high strength at a lower density. Fiber is a commonly used reinforcing phase in composites, which can compensate for the loss of strength. It inhibits the generation of microcracks in concrete and improves the overall performance of concrete.15 There are two main forms of fiber reinforcement, namely, matrix fiber reinforcement and filled fiber-reinforced hollow materials. Currently, the common filler fibers are mainly steel fibers,16 carbon fibers,17 glass fibers,18 basalt fibers (BFs),19 and polypropylene fibers (PPFs).20 Hassanpour et al.21 found that steel fibers can increase the compressive strength of lightweight concrete by 14–32%, the compressive strength by 21–77%, and the flexural strength by 6–69%. Ahmad et al.22 studied the effect of glass fibers on the mechanical properties of concrete and found that the incorporation of fibers increased the toughness and modulus of elasticity of concrete after damage. Glass fibers increased the compressive strength of concrete by 10.20% and compressive strength and flexural strength by 60.1 and 63.49%, respectively.

Basalt fiber23−26 is a new type of green inorganic fiber with good chemical stability, high compressive strength, corrosion resistance, and high modulus of elasticity. Basalt fibers have natural silicate compatibility. It has good bonding properties with the cement matrix and can improve the compressive strength and ductility of concrete. It inhibits plastic shrinkage of the concrete matrix.27 It is a good alternative to the steel fiber. Polypropylene fiber28,29 is a synthetic fiber with high ductility and strong deformation properties. It can reduce the plastic shrinkage of concrete and improve the ductility and durability of concrete. It has low cost and high corrosion resistance compared to those of steel fibers. Jiang et al.30 found that basalt fibers can increase the compressive strength of lightweight concrete by 39.8%. Bayraktar et al.31 investigated the effect of basalt fibers on the mechanical properties of foam concrete and found that basalt fibers have a positive effect on the compressive strength of foam concrete. The compressive strength was increased by 115.32 and 151.61% when basalt fibers were mixed at 1 and 2%, respectively, as compared to the control group. Chen et al.32 found that basalt fiber-reinforced polymers can improve the long-term flexural properties of ultrahigh-performance concrete (UHPC) and effectively mitigate the risk of degradation of UHPC mechanical properties due to corrosion in harsh environments. Mehrab et al.20 found that the mixing of polypropylene fibers was able to reduce the dependence of the strength of lightweight concrete on size effect parameters and increase the total fracture energy of lightweight concrete. Chen et al.33 investigated the effect of the macrobasalt fiber (MBF) content on the mechanical properties of ultrahigh-performance concrete (UHPC). It was found that the increase in the BMF content increased the toughness and compressive strength of UHPC.

In this study, a three-phase composite lightweight concrete was prepared by a combination of ball rolling methods and molding methods. This paper compares the compressive strength and density of lightweight concretes prepared under different conditions in terms of stack volume fraction of GFR-EMS, type of fibers, length, and content of added fibers in the HGMS–cement matrix. The compressive mechanism and optimum preparation parameters of lightweight concrete are analyzed by compression tests. This provides some insights into the development of lightweight concrete.

2. Experimental Part

2.1. Materials

Epoxy resin (Araldite LY 1564) and Amine curing agent (Aradur 3486) were purchased from Huntsman Chemical Co., Ltd., China. The mass ratio of epoxy resin and curing agent was 3:1. Silicate cement, strength grade 42.5, was purchased from Shanghai Qian Decoration Building Material Co., Ltd., China. The expanded polystyrene foam ball (EPS), with a diameter of 10–11 mm, was from Hangzhou Hangchao Packaging Material Co., Ltd., China. Basalt fibers and polypropylene fibers in lengths of 3, 6, 9, and 12 mm were purchased from Haining Anjie Composite Material Co., Ltd., China. Hollow glass beads, specification K1 grade, were from 3 M Company, USA.

2.2. Preparation Process of GFR-EMS

Figure 1 shows the schematic diagram of the preparation of GFR-EMS. The preparation process of GFR-EMS consists of mixing, pressing, and heating. First, the glass fiber powder was uniformly wrapped on the surface of EPS using epoxy resin and curing agent. Then, the glass fiber powder-wrapped EPS was put into the oven for step heating and cured at 50 °C for 2 h and 80 °C for 1 h to obtain GFR-EMS. The glass fiber powder forms a hard shell on the surface of EPS and EPS becomes stronger.

Figure 1.

Figure 1

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Schematic of the GFR-EMS preparation.

2.3. Preparation of Three-Phase Composite Lightweight Concrete

Figure 2 shows a schematic diagram of the preparation of a three-phase composite lightweight concrete. The preparation of lightweight concrete is divided into the following steps. First, the specified amount of silicate cement, fiber, and K1 grade HGMS was mixed dry and homogenized. Water was added in a ratio of 2:1 with silicate cement and mixed well to obtain the matrix. A quantitative amount of GFR-EMS was added to the matrix and mixed well to obtain the initial sample. Second, the well-mixed initial sample was filled into a mold with dimensions of 70.7 mm × 70.7 mm × 70.7 mm. The top of the mold was covered with polyester film to reduce air entry. Heavy weights were placed above the molds to flatten the specimen surface and to avoid uplift of the lightweight material. Finally, the specimens were demolded after 28 days of curing.

Figure 2.

Figure 2

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Schematic of the preparation of a three-phase composite lightweight concrete.

This experiment mainly compares the effects of different influencing factors on the properties of lightweight concrete. The influencing factors can be categorized as the stacking volume fraction of GFR-EMS, the types of fibers, the fiber content, and the length in the matrix. It is worth noting that the mass fraction is the ratio of the mass of fibers added to the lightweight concrete specimen to the mass of cement in the specimen. The specific element used for the experiments is shown in Table 1.

Table 1. Lightweight Concrete Specimens with Different Parameters.

sample HGMS (wt %) in filler cement (wt %) GFR-EMS (s vol %) GFR-EMS’s layers GFR-EMS diameter (mm) BF’s length (mm) BF (wt %) PPF length (mm) PPF (wt %)
1 K1–40 60   2 10–11        
2 K1–40 60 20 2 10–11        
3 K1–40 60 40 2 10–11        
4 K1–40 60 60 2 10–11        
5 K1–40 60 80 2 10–11        
6 K1–40 60 90 2 10–11        
7 K1–40 60 90 2 10–11 12 0.5    
8 K1–40 60 90 2 10–11 12 1.0    
9 K1–40 60 90 2 10–11 12 1.5    
10 K1–40 60 90 2 10–11 3 1.5    
11 K1–40 60 90 2 10–11 6 1.5    
12 K1–40 60 90 2 10–11 9 1.5    
13 K1–40 60 90 2 10–11     12 0.5
14 K1–40 60 90 2 10–11     12 1.0
15 K1–40 60 90 2 10–11     12 1.5
16 K1–40 60 90 2 10–11     3 1.5
17 K1–40 60 90 2 10–11     6 1.5
18 K1–40 60 90 2 10–11     9 1.5
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2.4. Characterization

2.4.1. Compressive Strength Testing

A universal testing machine (CMT5350, Shenzhen Sanshi Zongheng Technology Co., Ltd.) was used to test the lightweight concrete test blocks. The test standard was adopted from the Chinese GB/T50081-2019 standard. An electronic universal testing machine was used to control and measure the experimental force, deformation, displacement, and other factors. The loading rate is 1.5 KN/s. The maximum test force is up to 300 KN, and the maximum experimental range is up to 1100 mm. The compressive strength is calculated using eq 1

2.4.1. 1

where fc is the compressive strength, Fc,max is the maximum compressive load, and A is the pressure-bearing area.

2.4.2. Density Texting

A digital analytical balance (Guangzhou BGD Laboratory Instrument Supply Co.) was used to measure the mass of the sample. Digital vernier calipers were used to measure the length, width, and height of the samples. The average density of the sample was calculated using eq 2

2.4.2. 2

2.4.3. Fiber Morphological Characteristics

The basalt fibers were milled into a monofilament state before observation. The morphology of basalt fibers was observed by scanning electron microscopy (SEM) (JEM-4701, JEOL, Japan). Before SEM observation, the fibers were cleaned with an ultrasonic cleaner (SK2200H, Shanghai Kudos Ultrasonic Instruments Co., Ltd., China) to remove surface dust. A gold layer was sputtered onto the surface of the samples by means of a gold-spraying device (Sputter Coater) (ISC150) to make the samples more conducive for observation.

3. Results and Discussion

3.1. BF Macroscopic Morphology and Composition

Figure 3 shows the morphology of BF. It can be seen that the BF is brown in color and has a smooth surface. Figure 3b–f shows SEM photographs and energy spectra of the BF. BF monofilaments have a SiO2 particulate matter attached to the surface, which effectively improves the surface roughness of the fibers. The increased surface roughness increases the effective contact area and the bond between the fibers and the concrete matrix. The main components of BF are SiO2, Al2O3, MgO, and other metal oxides, which are chemically stable. It is not easy to react with other substances and have high-temperature resistance, corrosion resistance, and other properties.34

Figure 3.

Figure 3

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BF morphology: (a) BF photo, (b) BF SEM photo, and (c–e) BF energy spectra.

3.2. GFR-EMS Macroscopic Morphology and Density

Figure 4a shows the macroscopic morphology of the GFR-EMS. GFR-EMS is a regular sphere with a uniform particle size. The surface of the sphere is fine and free of defects and protrusions. This contributes to the mechanical strength of the EPS and the adhesion of the bond to the HGMS–cement matrix. It reduces gaps within lightweight concrete.

Figure 4.

Figure 4

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Characterization of the GFR-EMS: (a) macroscopic morphology of GFR-EMS and (b) density of GFR-EMS.

50 GFR-EMS were randomly selected for diameter and mass counts in order to minimize the experimental error. Figure 4b shows the density characterization of GFR-EMS. The average density of GFR-EMS is 0.536 g/m3. GFR-EMS replaces some of the aggregates in concrete. The density of lightweight concrete is reduced, and the dead weight is lowered.

3.3. Study on Compressive Strength and Density of Three-Phase Composite Lightweight Concrete under Different Influencing Factors

3.3.1. Stacked Volume Fraction of GFR-EMS

Lightweight aggregates affect the performance of lightweight concrete. The addition of lightweight aggregates makes the unit weight and strength of concrete lower. Figure 5 shows the compressive strength and density of a three-phase composite lightweight concrete with different stacking volume fractions of GFR-EMS. The compressive strength of the lightweight concrete at each filler volume fraction was 17.60 (0%), 11.12 (20%), 10.92 (40%), 6.42 (60%), 5.87 (80%), and 5.59 MPa (90%). The respective densities were 1.590 g/cm3 (0%), 1.516 g/cm3 (20%), 1.408 g/cm3 (40%), 1.263 g/cm3 (60%), 1.136 g/cm3 (80%), and 1.105 g/cm3 (90%). The results showed that the compressive strength of concrete decreased from 17.60 to 5.59 MPa. The decrease in compressive strength was related to the porous structure of concrete and the strength of GFR-EMS. Aggregates usually play the role of skeleton in concrete, and the inherent strength of GFR-EMS is low, which leads to the reduction of its compressive strength when replacing the cement matrix. The introduction of GFR-EMS made it easier to form a porous structure during the preparation of concrete. The compressive strength of concrete decreased by 36.82, 37.95, 63.52, 66.65, and 68.24% when the content of GFR-EMS was 20, 40, 60, 80, and 90%, respectively. An increase in the amount of GFR-EMS filling means that there is a higher probability that the GFR-EMS will come into contact with each other in the matrix. GFR-EMS in contact with each other will crush the protective cement matrix. The contact points of GFR-EMS are prone to breakage when subjected to external loads, causing damage inside the concrete matrix. The introduction of GFR-EMS also decreases the density of concrete from 1.590 to 1.105 g/cm3. As shown in Figure 5b, the increase of the GFR-EMS content implies the increase of pore defects and porous structure inside concrete. The porous structure and pore defects inside the concrete can effectively reduce the density.

Figure 5.

Figure 5

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Characterization of a three-phase composite lightweight concrete with different stacked volume fractions of GFR-EPS: (a) compressive strength and (b) density.

3.3.2. Filled Mass Fraction of BF and PPF

Figure 6 represents the compressive strength and density of a three-phase composite lightweight concrete filled with different mass fractions of BF and PPF. Figure 6a,b shows the compressive strength and density of lightweight concrete filled with different mass fractions of BF. It can be noted that the compressive strengths of the lightweight concrete filled with BF were 5.59 (0%), 7.45 (0.5%), 8.01 (1.0%), and 9.08 MPa (1.5%). The densities of each of them were 1.105 g/cm3 (0%), 1.155 g/cm3 (0.5%), 1.180 g/cm3 (1.0%), and 1.192 g/cm3 (1.5%). Figure 6c,d describes the compressive strength and density of lightweight concrete filled with different mass fractions of PPF. It can be observed that the compressive strengths of the filled PPF were 5.59 (0%), 6.92 (0.5%), 7.21 (1.0%), and 7.78 MPa (1.5%). The densities of each were 1.105 g/cm3 (0%), 1.187 g/cm3 (0.5%), 1.189 g/cm3 (1.0%), and 1.190 g/cm3 (1.5%). The results showed that fiber incorporation effectively increased the compressive strength of lightweight concrete. The compressive strength and density of the lightweight concrete increased as the mass fraction of fiber filling within the matrix increased. The compressive strength of concrete with BF added increased by 33.27, 43.29, and 62.43% when the mass fraction of the fiber was 0.5, 1.0, and 1.5%, respectively. The compressive strength of concrete with PPF added increased by 23.79, 28.98, and 39.18%, respectively. On the one hand, the fibers are able to fill the original crack gaps within the concrete and reduce the pore defects in the internal organization of the concrete. On the other hand, the introduction of fibers plays a connecting role inside the matrix to connect the originally dispersed matrix into a certain mesh structure. When the concrete is damaged by external forces, the mesh structure formed by the fibers can disperse and transfer the force more quickly to improve the compressive strength of the concrete. Fibers have a tensile effect that slows stress concentration and cracking and improves the ductility of concrete. The change in density is mainly related to the fiber content. The fiber itself is less dense. With less addition in the experiment, the density of concrete changes less. The compressive strength of concrete in this experiment increases with the increase in the fiber content. However, the fiber is not better, the more it is added. Experiments35 have shown that the fiber content should be kept within 5% for optimum results. Excessive fibers may reduce the strength of concrete. The addition of fiber in this experiment was only 1.5%, which did not reach the threshold for the experiment, and further research is needed.

Figure 6.

Figure 6

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Characterization of a three-phase composite lightweight concrete with different mass fractions of fibers: (a) BF-compressive strength, (b) BF-density, (c) PPF-compressive strength, and (d) PPF-density.

3.3.3. Filled with Different Lengths of BF and PPF

Longer fibers are more likely to form a reticular space structure in the matrix to inhibit the relative slip of the aggregate particles. Figure 7 illustrates the compressive strength and density of a three-phase composite lightweight concrete filled with different lengths of BF and PPF. Figure 7a,b displays the compressive strength and density of lightweight concrete filled with different lengths of BF. The apparent BF-compressive strengths of filled lightweight concrete were 5.59 MPa (0 mm), 7.12 MPa (3 mm), 7.88 MPa (6 mm), 8.78 MPa (9 mm), and 9.08 MPa (12 mm). The densities of each were 1.105 g/cm3 (0 mm), 1.156 g/cm3 (3 mm), 1.162 g/cm3 (6 mm), 1.175 g/cm3 (9 mm), and 1.192 g/cm3 (12 mm). Figure 7c,d presents the compressive strength and density of composite lightweight concrete filled with different lengths of PPF. It is evident that the compressive strength of PPF-filled lightweight concrete was 5.59 MPa (0 mm), 6.98 MPa (3 mm), 7.06 MPa (6 mm), 7.69 MPa (9 mm), and 7.78 MPa (12 mm) and the respective densities were 1.105 g/cm3 (0 mm), 1.160 g/cm3 (3 mm), 1.170 g/cm3 (6 mm), 1.185 g/cm3 (9 mm), and 1.190 g/cm3 (12 mm). The results showed that the compressive strength of the lightweight concrete increased with an increase in the length of the fibers. When the length of the fibers was 12 mm, the compressive strength of the BF-filled lightweight concrete increased by 62.43% and that of the PPF-filled lightweight concrete increased by 38.18%. Fibers can have adhesion and shrinkage effects on the concrete matrix, resulting in different stress states in the matrix. Short fibers can form only a smaller bond and friction effect with the matrix. Sliding is more likely to occur between the fibers and the matrix, reducing the restraining effect of the fibers on the concrete. No significant increase in compressive strength can be realized. Long fibers are able to form a larger contact area with the matrix. This creates greater friction during the relative movement of the concrete and prevents the matrix from being damaged. Longer fibers also increase the connectivity between the matrices within the matrix. The fibers are more likely to overlap with each other and form a mesh structure that acts as a “bridge” between the matrices,36,37 inhibiting the relative slip between the matrices. This improves the mechanical properties of concrete and improves the brittleness of the specimens.

Figure 7.

Figure 7

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Characterization of the compressive strength and density of a three-phase composite lightweight concrete filled with BF and PPF of different lengths: (a) BF-compressive strength, (b) BF-density, (c) PPF-compressive strength, and (d) PPF-density.

3.4. Comparison

Density and compressive strength are two conflicting points of lightweight concrete. These two properties can only seek the optimal ratio of the equilibrium point so that the concrete can have high strength at lower density. The effect of GFR-EMS, BF, and PPF on the properties of lightweight concrete is seen more clearly. The density and compressive strength of lightweight concrete with different parameters are summarized in Figure 8a. As can be seen from the data, the filling of the GFR-EMS was able to reduce the density of the concrete. This is mainly due to the honeycomb structure formed by the GFR-EMS inside the concrete. The reduction in density also brings about a reduction in the strength of the lightweight concrete. The introduction of fibers reduces the breakdown of concrete strength due to the filling of lightweight aggregates. The compressive strength of the lightweight concrete increased by 27.53% when the length of the admixed BF was 12 mm (1.5%) as compared to the admixed 3 mm BF (1.5%). It was increased by 21.88% as compared to the admixture of 0.5% BF (12 mm). Long fibers increase the possibility of fiber-to-fiber connectivity.38 The high content of fibers enables the formation of stronger connections between the matrices. The stronger ability of fibers forms a mesh structure inside the matrix. The mesh structure quickly disperses the force when it is damaged by external forces, reduces the concentration of stresses, and improves the compressive capacity. The effects of different fibers on the strength of lightweight concrete are compared. The results showed that the compressive strength of BF-filled lightweight concrete increased by 16.71% compared to that of PPF-filled BF and showed to be more effective in improving the strength of lightweight concrete. On the one hand, BF has a higher modulus of elasticity and tensile strength than PPF. On the other hand, the composition and density of BF are close to that of cement. Monofilaments with a diameter smaller than that of PPF are uniformly dispersed in the cement matrix to form a dense, chaotically distributed reticular support structure system. A large number of hydration products attached to the fibers increase the friction and bite of the fiber surface. There is a higher bonding force with the cement matrix, and it is easier to form a whole. The hydration products on the fiber surface can also fill the pore defects inside the concrete and increase the compactness. The compressive strength of the concrete is improved.39 As can be seen in Figure 8b, the work allows for higher compressive strengths at lower densities.22,38−42

Figure 8.

Figure 8

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(a) Comparison of the density and compressive strength of a three-phase composite lightweight concrete with different parameters. (b) Comparing the density and compressive strength of our work with the representative fiber-reinforced lightweight concrete reported in the literature.

3.5. Compressive Mechanism of Composite Lightweight Concrete with GFR-EMS and Fiber Filling

Figure 9 demonstrates the compressive mechanism of a composite lightweight concrete filled with GFR-EMS and fibers. Figure 9a shows the compressive mechanism of 20% GFR-EMS stacked on lightweight concrete. As can be seen in Figure 9a, GFR-EMS is relatively dispersed in the 20% GFR-EMS-filled lightweight concrete. The lightweight concrete is still based on HGMS–cement as the main matrix. Even if an external load is transmitted to the GFR-EMS, the GFR-EMS is protected from destruction by the matrix because the GFR-EMS and the matrix are still one. Figure 9b shows the compressive mechanism of lightweight concrete filled with 90% GFR-EMS. The 90% GFR-EMS-filled lightweight concrete has a dense distribution of GFR-EMS. Some of the GFR-EMS were connected to each other close to form lines. When lightweight concrete is impacted by an external force, the force is rapidly transferred from the concrete matrix to the GFR-EMS and from the GFR-EMS to the cement matrix or another GFR-EMS.43 The strength of the GFR-EMS is lower than that of the cementitious matrix. Damage begins with the GFR-EMS and then passes rapidly to the next GFR-EMS or the adjacent matrix above. GFR-EMS in contact with each other squeezed off the protective cement matrix. Their contact points are prone to brittle damage. Stress concentration occurs at the point of damage, and the concrete is eventually damaged with the addition of fibers into it, as shown in Figure 9c. The mesh space structure formed by the fibers inside the concrete matrix interconnects the cement matrix with the cement matrix, the cement matrix with the GFR-EMS, and the GFR-EMS with the GFR-EMS into a whole. The presence of a mesh structure disperses and transmits forces. Due to the redistribution of the bearing capacity and the crack stopping effect of the fibers, the matrix damage mode changes from brittle to ductile damage.44 Cracks gradually develop with the increase in external force. Stress begins to be transferred through interfacial shear when the crack is close to the fiber.45,46 The force starts to disperse in the direction of the fibers, and finally all of the stress is gradually transferred to the fibers.47,48 The presence of fibers retards the first crack. The strength of the concrete is improved.

Figure 9.

Figure 9

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Compressive mechanism diagram of lightweight concrete under different conditions: (a) 20%-GFR-EMS, (b) 90%-GFR-EMS, and (c) 90%-GFR-EMS-fiber.

4. Conclusions

In this experiment, GFR-EMS, HGMS, BF, and PPF were used as materials to prepare a three-phase composite lightweight concrete using a combination of the ball method and the molding methods. The work investigates the various influencing factors such as the stacking volume fraction of GFR-EMS, the type of fiber, and the content and length of fiber in the matrix. The experimental results show that the introduction of GFR-EMS decreases the density of concrete from 1.590 to 1.105 g/cm3. The compressive strength decreases from 17.60 to 5.59 MPa. The decrease in density also brings about the destruction of the compressive strength. The introduction of fibers increased the compressive strength of lightweight concrete by 62.43%, which had a positive effect on improving the mechanical properties of the concrete. The density and compressive strength of lightweight concrete increased with the increase of fiber length and mass fraction. The compressive strength of the lightweight concrete increased by 27.53% when the length of the admixed BF was 12 mm (1.5%) as compared to the admixed 3 mm BF (1.5%). It was increased by 21.88% as compared to the admixture of 0.5% BF (12 mm). The fibers can fill pore defects within the matrix. The long fibers are more likely to lap each other to form a mesh structure, which improves the bonding between the matrices. BF showed more effective results in improving the mechanical properties of lightweight concrete. The compressive strength of BF-filled lightweight concrete increased by 16.71% compared to that of PPF-filled. In this work, the effect of fiber content and fiber length on the strength of lightweight concrete was investigated within a certain range. The compressive strength of lightweight concrete is enhanced with an increase in fiber content and length. This experiment did not explore the threshold value of the fiber content, which needs to be further explored in future experiments. In addition, the tensile strength, flexural strength, and modulus of elasticity of concrete are also important indicators of concrete. These need to be combined in future experiments to consider the overall performance of concrete in a comprehensive manner.

Acknowledgments

This work was financially supported by the Science and Technology Commission of Shanghai Municipality and Shanghai Engineering Research Center of Ship Intelligent Maintenance and Energy Efficiency under (20DZ2252300) and the Shanghai High-level Local University Innovation Team (Maritime safety and technical support).

Data Availability Statement

All data, models, and code generated or used during the study appear in the submitted article.

Author Contributions

∥ S.X. and K.Y. contributed equally to this work. S.X.: data curation, writing—original draft, and writing—review and editing. K.Y.: data curation and writing—review and editing. T.J.: methodology, validation, and investigation. Y.W.: methodology, validation, and investigation. S.S.: methodology, validation, and investigation. W.L.: conceptualization, methodology, writing—review and editing, and funding acquisition. Y.Z.: methodology, validation, and investigation. K.S.: methodology, validation, and investigation. J.Y.: conceptualization, methodology, and writing—review and editing. X.W.: conceptualization, methodology, validation, writing—review and editing, and funding acquisition.

The authors declare no competing financial interest.

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