Effect of Basalt Fiber on the Performance of Permeable Concrete
Basalt fiber, as a novel inorganic, high-performance, and eco-friendly material, significantly enhances the mechanical properties, durability, and functionality of permeable concrete. Below is a multidimensional analysis of its impacts and optimization parameters:
- Impact on Mechanical Properties
Improved Compressive and Flexural Strength
Basalt fiber reinforcement effectively enhances the compressive and flexural strength of permeable concrete. Studies indicate that fibers form a three-dimensional network structure, strengthening the bonding between aggregates and cement paste while inhibiting crack propagation. For example:
Compressive Strength: With 12 mm and 24 mm fibers, compressive strength initially increases and then decreases with higher fiber content. The optimal dosage is 0.1%–0.15% (by volume), with 24 mm fibers achieving a peak compressive strength of 24.3 MPa (at 0.1% dosage).
Flexural Strength: Fiber length has a more pronounced effect on flexural strength. For instance, 18 mm fibers increase flexural strength by 66.44% compared to plain concrete due to enhanced interfacial bonding from increased fiber-aggregate contact.
Enhanced Toughness and Ductility
The "bridging effect" of Basalt Fibers improves toughness, shifting failure modes from brittle to ductile. Microscopic analysis reveals that fibers stabilize the skeleton structure within the cement matrix, effectively blocking crack growth.
Impact on Permeability
Reduced Permeability Coefficient
Fiber incorporation partially blocks pores, lowering permeability. For example, increasing fiber content from 0.05% to 0.2% gradually reduces the permeability coefficient, yet it still meets specifications (e.g., permeability >1 mm/s at 20% porosity).
Balancing Porosity and Fiber Parameters
Longer fibers (e.g., 12 mm → 24 mm) slightly increase porosity but still reduce permeability.
Combining fibers with mineral admixtures (e.g., fly ash) optimizes pore structure, minimizing permeability loss while maintaining strength.
- Improved Frost Resistance
Basalt fibers enhance internal structural integrity, significantly boosting frost resistance:
After 100 freeze-thaw cycles, fiber-reinforced specimens exhibit a mass loss rate as low as 0.9% and retain 62.5% relative dynamic elastic modulus.
Synergy with fly ash (e.g., 6% fly ash + 6 kg/m³ fibers) achieves optimal frost resistance, as fly ash refines pore structure while fibers suppress freeze-thaw cracking.
- Key Optimization Parameters
Fiber Length: 24 mm fibers are recommended for balancing strength and permeability, though 18 mm fibers excel in flexural strength.
Dosage Range: 0.1%–0.15% by volume (or 2–6 kg/m³ by mass). Excessive dosage risks fiber agglomeration and reduced workability.
Synergistic Materials: Fly ash (6%–15%) or silica fume (6%–9%) further enhance mechanical properties and mitigate permeability loss.
- Application Recommendations
Scenarios: Ideal for pedestrian walkways, plazas, and cold regions requiring both permeability and strength.
Construction: Use the "cement-coated aggregate" mixing method to ensure uniform fiber dispersion and avoid clumping.
In summary, basalt fiber optimizes the microstructure and mechanical performance of permeable concrete, but strict control of dosage and process parameters is critical to balance strength and permeability. Future research should focus on fiber surface modification and multi-material synergy to overcome current performance limitations.
