An Experimental Study of the Use of EPS in Bituminous Mixes Prepared with RAP

Abstract

This study explores the combined use of Reclaimed Asphalt Pavement (RAP) and Expanded Polystyrene (EPS) as sustainable and performance-enhancing materials in Bituminous Concrete Grade-2. With the growing focus on environmentally friendly road construction, the use of RAP helps reduce the consumption of virgin aggregates and bitumen, while also minimizing waste generation and energy use. EPS, a lightweight and recyclable plastic waste, is known to improve the stiffness and thermal resistance of bitumen when used as a modifier. The experimental program began with the sample being prepared for a control mix with varying binder content. The optimum binder content for the control mix was determined to be 5.65% using the Marshall Method. Subsequently, modified bituminous mixes were prepared by incorporating RAP at 27.5%, 30%, and 32.5%, and EPS at varying contents from 3% to 7%. Laboratory testing was conducted in accordance with ASTM standards. It included Marshall Stability, Flow Value, Bulk Density, Air Voids, VMA, VFB, and ITS. The results indicated that the inclusion of RAP increased the stability of the mix and reduced the requirement for fresh binder due to the presence of aged bitumen. The addition of EPS resulted in an increase in the softening point and a decrease in the penetration value, indicating improved stiffness and resistance to high temperatures. Overall, the optimum use of 27.5% RAP and 5% EPS produced bituminous mixes with higher stability, desirable air void content, improved crack resistance, and enhanced tensile strength compared to conventional mixes. The study concludes that RAP and EPS can be effectively utilized in bituminous concrete to lower environmental impact and reduce material costs. These findings support the use of recycled materials in highway construction and highlight the need for further research on the long-term field performance and optimization of RAP–EPS proportions for practical applications.

Introduction

Asphalt pavements are widely used due to their durability and ease of maintenance, and incorporating recycled materials such as Reclaimed Asphalt Pavement (RAP) and Expanded Polystyrene (EPS) helps conserve natural resources and reduce environmental impacts. RAP consists of reclaimed aggregates and aged bitumen from existing pavements, while EPS, a lightweight polymer waste, is used as a bitumen modifier to improve stiffness, thermal resistance, and deformation resistance, especially over weak subgrades.

The literature review shows that both RAP and EPS have been successfully used to enhance asphalt performance. Studies report improved Marshall stability, stiffness, and sustainability at optimal RAP contents (commonly 30–75%) and EPS contents (generally 0.5–5%). However, excessive amounts can reduce performance. Despite extensive research, gaps remain regarding the optimal combined use of RAP and EPS, their behavior with different binder grades, detailed engineering property evaluation, and application across different asphalt mix types.

The objectives of the study are to determine the optimum binder content for Bituminous Concrete Grade-2 with and without RAP, evaluate Marshall and indirect tensile strength properties for mixes containing RAP and EPS, and identify the optimal RAP–EPS combination.

Experimental work used VG-30 bitumen, natural aggregates, and RAP aggregates, all meeting relevant Indian standards. EPS-modified bindumen showed reduced penetration and increased softening point with increasing EPS content, indicating stiffer binders. Marshall mix design for the control mix established an optimum binder content of 5.65%, providing balanced stability, flow, and air voids. When RAP was introduced (27.5–32.5%), the required fresh bitumen content decreased due to the contribution of aged binder from RAP.

Conclusion

The following conclusions have been derived after analyzing the test results: 1) Among the tested binder contents of 5.40%,5.65%, 5.80% and 5.95% for the control mix, the optimum binder content was determined to be 5.65%, indicating the most suitable proportion for achieving the desired mix properties. 2) EPS did not mix homogenously with VG-30 bitumen; it formed flocculates on top when mixed with VG-30 3) It was found that the physical properties of bitumen, such as penetration and softening point, were improved with the addition of EPS. EPS modified VG-30 gives a lower penetration value and a higher softening point value as compared to Virgin VG-30 Bitumen 4) For the mix containing 27.5% RAP, the stability value was 21.48 kN. When EPS was incorporated into the 27.5% RAP mix, the stability value increased to 28.32 kN at 5 % EPS content. 5) Performance Enhancement: Adding EPS up to 5% significantly improved stability, tensile strength, and temperature resistance of the mix without compromising workability or compaction 6) Indirect tensile strength decreased from 0.91N/mm2 at 27.5% RAP to 0.86N/mm2 at 32.5% RAP. Tensile strength has reduced, making it less resistant to cracking under load. 7) Indirect tensile strength increased from 1.06N/mm2 at 3% EPS to 1.18N/mm2 at 5% EPS, indicating improved resistance to cracking and tensile under load.

References

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Copyright

Copyright © 2026 Er. Akshit Thakur, Er. Ajay Kumar Duggal. 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.