Evaluating the Effect of Glass Grid Interface in DBM and BC with Recycled Bituminous Mix

Abstract

Sustainable pavement engineering has become an essential requirement in modern transportation infrastructure due to rapid urbanization, increasing traffic demand, depletion of natural resources, and growing environmental concerns associated with conventional road construction. This research investigates the performance of flexible pavement mixes prepared using 30% Reclaimed Asphalt Pavement (RAP) and reinforced with glass grid at the interface of Dense Bituminous Macadam (DBM) and Bituminous Concrete (BC) layers using VG-30 and VG-40 bitumen. The study demonstrates that for BC mix, glass grid reinforcement significantly enhances Marshall Stability by 36% with VG-30 (24.21 kN to 32.93 kN) and 21.2% with VG-40 (21.92 kN to 26.57 kN). Composite BC-DBM systems exhibited stability improvements of 6.7% and 7.1% for VG-30 and VG-40 binders respectively compared to its counterpart. ITS values increased from 13.50 kPa to 15.03 kPa (VG-30 BC) and from 19.36 kPa to 23.69 kPa (VG-40 composite), indicating enhanced tensile crack resistance. All reinforced mixes satisfied IRC volumetric requirements with air voids maintained between 3-4% and VMA above minimum specifications. The findings establish that 30% RAP with glass grid reinforcement is technically feasible, structurally beneficial, and promotes sustainable construction practices without compromising pavement performance.

Introduction

The study focuses on improving the durability and sustainability of flexible pavements by incorporating Reclaimed Asphalt Pavement (RAP) and glass grid reinforcement. Increasing traffic loads and environmental concerns have created a need for pavement materials that reduce dependence on virgin aggregates and petroleum-based binders. RAP helps conserve resources and reduce waste, while glass grid reinforcement improves tensile strength, crack resistance, stress distribution, and rutting performance.

Although RAP and glass grids have been studied separately, their combined effect in RAP-modified composite pavement systems, particularly at the Bituminous Concrete (BC)–Dense Bituminous Macadam (DBM) interface, has not been sufficiently explored. This research investigates the performance of BC Grade-1 and DBM Grade-2 mixtures containing 30% RAP and reinforced with a glass grid placed at the BC–DBM interface. Two binder grades, VG-30 and VG-40, are evaluated to study the influence of binder stiffness.

Literature Findings

Previous research indicates that:

• RAP improves stiffness, rutting resistance, sustainability, and reduces construction costs, but excessive RAP may increase brittleness and reduce fatigue performance.
• Glass grid reinforcement improves pavement strength by enhancing tensile resistance, delaying crack propagation, reducing rutting, and improving fatigue life.
• The effectiveness of reinforcement depends strongly on its placement, bonding, and compatibility with pavement layers.
• Limited research exists on combining RAP with glass grid reinforcement in composite BC–DBM pavement systems.

Research Objectives

The study aims to:

1. Prepare RAP-modified BC and DBM mixes using VG-30 and VG-40 bitumen.
2. Develop glass grid reinforced BC and composite BC–DBM mixtures.
3. Evaluate pavement properties using:
   • Marshall Stability and Flow tests
   • Volumetric analysis
   • Indirect Tensile Strength (ITS)
   • Resilient Modulus evaluation
4. Analyse the effect of glass grid placement at the BC–DBM interface.
5. Compare reinforced and unreinforced pavement performance.

Methodology

The experimental program follows the Marshall mix design method according to MoRTH specifications.

The study includes five specimen types:

1. BC Grade-1 control mix
2. DBM Grade-2 control mix
3. BC mix reinforced with glass grid
4. Composite BC–DBM mix without reinforcement
5. Composite BC–DBM mix with glass grid reinforcement

Each mixture contains 30% RAP and is prepared using VG-30 and VG-40 binders. Samples are tested for strength, durability, and deformation resistance.

Material Testing

The research evaluates:

• Bitumen properties: penetration, softening point, and specific gravity.
• Aggregate properties: specific gravity, impact value, flakiness, elongation, water absorption, and abrasion resistance.
• RAP properties: specific gravity, impact value, and recovered bitumen content.

The materials satisfy relevant IRC and IS specifications.

Expected Contribution

The study provides experimental evidence on whether placing glass grid reinforcement at the BC–DBM interface improves the performance of RAP-based flexible pavements. The research contributes toward developing stronger, longer-lasting, and environmentally sustainable pavement systems by combining recycled materials with reinforcement technology.

Conclusion

1) The optimum binder content (OBC) was established as 4.38% for BC (VG30), 4.45% for BC (VG40), 4.07% for DBM (VG30), and 4.15% for DBM (VG40) based on the Marshall mix design procedure. The reduction in binder content values are attributed to use of RAP. 2) Using 30% RAP in BC and DBM mixes is acceptable without compromising the requirements of IRC and MoRTH specifications. 3) Glass grid reinforcement enhanced the Marshall performance of both BC and composite mixes. The BC mix with VG30 exhibited the highest improvement in Marshall Stability, whereas the composite mix with VG40 achieved the highest overall stability among the reinforced specimens. 4) Reinforced composite specimens exhibited improved Stability values which may be due to improved interlayer bonding and stress transfer at the BC-DBM interface, resulting in higher load-carrying capacity. The reinforced mixes showed improved volumetric characteristics, including slightly higher density, lower air voids, and higher VFB, indicating better compaction and binder distribution while maintaining the required mix design criteria. 5) Glass grid reinforcement increased the Indirect Tensile Strength (ITS) of all mixes, indicating improved resistance to tensile stresses, fatigue cracking, and reflective cracking. The highest ITS was obtained for the reinforced composite VG40 mix. 6) A marginal increase in Resilient Modulus was observed for all reinforced specimens, indicating improved elastic response under repeated loading. The highest resilient modulus was also recorded for the reinforced composite VG40 mix. 7) The comparative evaluation showed that VG30 mixes exhibited greater relative improvement after reinforcement, whereas VG40 mixes provided higher overall structural capacity because of the higher stiffness of the binder. 8) The combined use of 30% RAP and glass grid reinforcement offers a technically feasible and sustainable approach for flexible pavement construction. Among all the mixtures evaluated, the reinforced composite VG40 mix demonstrated the best overall performance and is recommended for pavements subjected to heavy traffic and high service temperatures. 9) The combined use of RAP and glass grid reinforcement can reduce the consumption of virgin aggregates and bitumen, lower construction waste and improve the overall sustainability of flexible pavement construction

References

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Copyright

Copyright © 2026 Er. Naman Kumar Jaswal, 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.