Study on the Effect of Polypropylene Fibers on Mechanical Properties of Pervious Concrete

Journal: Jilin Jianzhu University, Vol. 42, No. 5, Oct. 2025 Authors: ZHANG Yongsheng¹, YU Genhai¹, ZHANG Shengyang¹, WANG Weihua¹, SHAN Jingsong²*, LIU Jian³ Affiliations:

1. Shandong Highway and Bridge Construction Group Co., Ltd., Jinan 250014, China
2. School of Civil Engineering and Architecture, Shandong University of Science and Technology, Qingdao 266590, China
3. China Communications Mechanical and Electrical Engineering Bureau Co., Ltd., Beijing 101300, China

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🔍 Abstract

To investigate the influence of fibers on the performance of pervious concrete, researchers prepared permeable concrete using cement as the base material, basalt as aggregate, and coarse/fine polypropylene fibers as reinforcement. By measuring the water permeability coefficient, compressive strength, and flexural strength, the study analyzed the effects of single and mixed fiber incorporation on permeability and mechanical properties, aiming to determine optimal fiber parameters. Key Findings:

• Coarse fibers (25 mm) and fine fibers (6 mm) had the most significant impact on the water permeability coefficient.
• Coarse fibers provided the highest improvement in compressive strength, with optimal parameters being 30 mm length and 4.5 kg/m³ dosage.
• Mixed fibers achieved the best enhancement in flexural strength, with optimal parameters being fine fibers (9 mm) combined with coarse fibers (25 mm) at a total dosage of 5.0 kg/m³ (fine:coarse = 1:4).
• Fiber parameters should be selected based on specific pavement requirements.

Microscopic analysis revealed that fiber incorporation effectively suppressed crack initiation and unidirectional propagation. Coarse fibers exhibited the most pronounced meso-level toughening effect, while mixed fibers showed less significant toughening compared to single fiber incorporation. Keywords: pervious concrete, fiber, performance, compressive strength, flexural strength

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🧪 Introduction

Pervious concrete, known for its high connectivity of internal voids, offers excellent water permeability. However, these voids reduce its strength. Incorporating polypropylene fibers can enhance mechanical properties, with fiber length and diameter influencing flexural and tensile strength. The addition of fibers also alters the fluidity of the cement paste, thereby affecting the effective porosity. Understanding the impact of fibers on the performance of pervious concrete is of great practical significance.

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🧱 Materials and Methods

Raw Materials and Mix Proportions

• Cement: P·O 42.5 Portland cement.
• Aggregate: Two sizes of basalt aggregate (2.35–4.75 mm, 4.75–9.5 mm).
• Fibers: White polypropylene fibers (physical properties shown in Table 1).
• Water: Tap water.

Table 1: Physical Properties of Polypropylene Fiber

Material	Density (g/cm³)	Diameter (μm)	Length (mm)	Tensile Strength (MPa)	Elastic Modulus (GPa)	Elongation at Break (%)
Fine PP Fiber	0.90	44.1	6, 9, 12	606	5.7	35
Coarse PP Fiber	0.91	870	25, 30, 35	525	7.0	21

Mix Design and Specimen Preparation

• Water-cement ratio: 0.30.
• Design void ratios: 18%, 23%, 28%.
• Fiber dosages:
  • Fine fiber: 1.5 kg/m³
  • Coarse fiber: 4.5 kg/m³
  • Mixed fiber: 5.0 kg/m³ (fine:coarse = 1:4)

Specimens were compacted using a manual hammering method, as illustrated below:

Figure 2: Compaction method and molded specimens

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📊 Performance Testing

1. Permeability Coefficient

Measured using the constant-head method according to CJJ/T 135-2009. Results showed that fiber incorporation slightly reduced permeability, with fine fibers (6 mm) causing a 28.40% decrease at 18% void ratio.

2. Compressive Strength

Tested at 7 days using a rock triaxial testing machine. Coarse fibers (30 mm) increased compressive strength by up to 32.51% at 18% void ratio.

3. Flexural Strength

Tested at 28 days using a four-point bending setup. Mixed fibers achieved the highest improvement (36.62%) at 5.0 kg/m³ dosage.

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🔬 Fiber Effects on Internal Void Structure

Fibers improved crack resistance and prevented severe spalling. Fine fibers formed a 3D network, delaying crack propagation, while coarse fibers acted as “bridges,” enhancing toughness. However, mixed fibers showed uneven distribution, reducing overall strength.

Figure 9: Failure states of pervious concrete specimens

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✅ Conclusions

1. Fiber incorporation reduces permeability but enhances mechanical properties.
2. Coarse fibers are optimal for compressive strength; mixed fibers are best for flexural strength.
3. Fibers improve crack resistance, with single fiber incorporation recommended for practical applications due to better uniformity.

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📚 References

[1] Mao Mingjie, et al. Study on preparation and aggregate-related performance of pervious concrete. Building Structure, 2022. [2] Yu Yongxia. Application of pervious concrete in sponge city construction. Anhui University of Science and Technology, 2016. [3] Elavarasan S, et al. Experimental studies on pervious concrete reinforced with polypropylene fiber. Materials Today: Proceedings, 2022. … (Additional references available in the original text)

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🔗 Further Reading

For detailed experimental data and methodology, refer to the full text in Journal of Jilin Jianzhu University, 2025, 42(5): 26–34.

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Cite this article: ZHANG Yongsheng, et al. Study on the effect of polypropylene fibers on the mechanical properties of pervious concrete. Journal of Jilin Jianzhu University, 2025, 42(5): 26–34.