The Impact of Footwear Waste on Modified Bitumen Mix

Abstract

This study investigates the potential of utilizing footwear waste as a sustainable modifier in bitumen to enhance its properties for road construction. With millions of tons of footwear waste accumulating in landfills each year, this approach offers a dual benefit—environmental sustainability and improved road performance. Modified bitumen samples were prepared with varying proportions of footwear waste and tested for penetration, softening point, ductility, viscosity, and Marshall Stability. Results demonstrated improved elasticity, temperature resistance, and overall stability. The findings suggest that incorporating footwear waste can significantly enhance the performance of bitumen, offering a viable, eco-friendly alternative in road infrastructure.

Introduction

Background:
Rapid urbanization and industrial growth have increased footwear waste, mainly non-biodegradable rubber and polyurethane, causing environmental pollution in landfills. Traditional bitumen used in road construction has limitations under extreme conditions. This study investigates using shredded footwear waste as a modifier in bitumen to improve its properties and promote sustainable road construction.

Objectives:

1. Assess the feasibility of using footwear waste as a bitumen modifier.

2. Evaluate effects on bitumen properties—penetration, softening point, ductility.

3. Test mechanical performance of modified mixes via Marshall Stability.

4. Compare modified bitumen with conventional bitumen mixes.

5. Identify the optimal footwear waste percentage for best performance.

Materials and Methods:

• VG30 grade bitumen, local aggregates, and shredded footwear waste collected and prepared.

• Footwear waste replaced bitumen at 2%, 3%, 5%, and 7% by weight.

• Standard Marshall method used to prepare and test specimens.

• Basic tests performed on aggregates and bitumen; modified bitumen mixed by heating and blending footwear waste.

• Stability, flow, density, and voids analyzed to evaluate mix performance.

Results:

• Marshall Stability: Peak stability (90.12 kN) achieved at 3% footwear waste replacement, indicating improved strength. Stability decreased beyond 3%.

• Flow Values: Decreased with increasing footwear waste up to 3%, showing improved stiffness and deformation resistance. Beyond 3%, flow reduction slowed, suggesting excessive stiffness that may reduce flexibility.

• Voids and Density: Values stayed within acceptable limits across all mixes, ensuring durability and compaction.

• Optimal footwear waste content identified at 3% for balanced strength, flexibility, and durability.

Conclusion

This study explores the utilization of footwear waste as a sustainable modifier in bitumen, offering an environmentally beneficial approach to road construction. By replacing a portion of bitumen with shredded footwear waste, the research evaluates the mechanical and structural properties of modified bituminous mixes and assesses their feasibility for pavement applications. The Marshall Stability analysis demonstrated that stability values increase with the addition of up to 3% footwear waste, reaching the highest value of 90.12 kN. The analysis of voids in the modified mix, including air voids, voids in mineral aggregates, and voids filled with bitumen, revealed a significant influence of footwear waste content. The air voids (Vv) initially decreased, suggesting improved compaction and density, particularly at 3% to 5% modification levels. However, beyond 5%, excessive voids led to a reduction in durability. The voids in mineral aggregates (VMA) and voids filled with bitumen (VFB) showed acceptable variations within the permissible range, ensuring sufficient bitumen retention and overall mix stability. Density measurements indicated a gradual increase up to 5% footwear waste content, suggesting improved material bonding. However, beyond this level, a reduction in density was observed, which could negatively impact long-term pavement performance. In future more Field trials and long-term durability tests are essential to validate laboratory findings and assess the practicality of using footwear waste in large-scale road construction projects.

References

[1] Amurag, V. I., and Rao, Y. R. M. (2017). \"Study of plastic waste mixed bituminous concrete using dry process for road construction.The Asian Review of Civil Engineering, 6(2),11-20 [2] Chen, Xiao and Wang, Hao.(2024) Asphalt pavement pothole repair with recycled material and preheating : Laboratory and field evaluation. In: Journal of Cleaner Production, 434 ,6-49. [3] Feng, Z., and Zhao, Z. (2021). \"Construction and Building Materials: Preparation and properties of bitumen modified with waste rubber pyrolytic carbon black.\" 282(89),12-36 [4] Bureau of Indian Standards. (1978). IS 1203-1978: Method of Testing Tar and Bituminous Materials. [5] Bureau of Indian Standards. (2004). IS 2386-4: Methods of test for aggregates for concrete, Part 4: Mechanical properties [6] Indian Roads Congress. (2009). IRC 111-2009: Specification for dense graded bituminous mixes. [7] Indian Roads Congress. (2010). IRC SP 053: Guidelines on Use of Modified Bitumen in Road Construction. .

Copyright

Copyright © 2025 Nikhil B, Shabana Shibin KK, Nihal Thamarath, Hafiz Javad, Fathimath Binsiya. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.