Use of Waste Plastic in Bituminous Mix – Field Methodology & Quality Test Checklist (India 2025)
Use of Waste Plastic in Bituminous Mix is a sustainable and cost-effective technique increasingly adopted in India’s highway construction. This innovative method improves the strength, durability, and rutting resistance of bituminous pavements while addressing the issue of plastic waste disposal. Under MoRTH Circular RW/NH-33041/2015/S&R(R) and IRC:SP:98-2022, waste plastic is blended with hot aggregates before bitumen mixing to create a strong, long-lasting road surface.
Why Use Waste Plastic in Bituminous Mix?
| Benefit | Description |
|---|
| Improved Durability | Plastic coating enhances aggregate binding and minimizes rutting. |
| Water Resistance | Reduces permeability and moisture-induced damage. |
| Higher Stability | Boosts Marshall Stability values by 10–15 %. |
| Sustainable Practice | Converts non-recyclable plastic into road material, supporting green-road missions. |
| Cost Savings | Lowers bitumen consumption by 8–10 %. |
MoRTH Reference:
Circular No. RW/NH-33041/20/2016-S&R(R) Pt. III – Guidelines for the Use of Waste Plastic in Hot Bituminous Mixes (as per IRC:SP:98-2013).
Step-by-Step Field Methodology
Step 1 – Collection and Segregation
- Collect clean, dry polyethylene and polypropylene waste (carry bags, cups, films).
- Avoid PVC, PET, or thermosetting plastics because they release harmful gases on heating.
- Shred into 2–4 mm pieces using a mechanical shredder — a compact rotary-blade machine designed to cut plastic uniformly for better coating.
Step 2 – Mixing with Hot Aggregates
- Heat aggregates to 150–160 °C in the hot-mix plant.
- Add shredded plastic in the dry-mix zone, allowing it to melt and form a thin coating on aggregate surfaces before bitumen is added.
- Mix for 30–40 seconds until coating appears uniform and glossy.
Step 3 – Addition of Bitumen
- Heat bitumen to 160–170 °C and add it to the plastic-coated aggregates.
- Blend for 45–60 seconds in the pugmill for full homogenization.
- Maintain plastic dosage at 6–8 % of the bitumen weight.
Step 4 – Laying and Compaction
- Transport the mix at 130–140 °C.
- Lay using a sensor paver for accurate level and thickness.
- Compact with tandem and vibratory rollers to achieve ≥ 98 % of laboratory density as required under MoRTH Clause 507.3.7.
Quality Test Checklist (MoRTH & IS Codes)
| S. No | Test Name | Reference | Frequency | Acceptance Criteria |
|---|
| 1 | Penetration Test | IS 1203 | 1 / 20 t | 60–80 mm (VG-30) |
| 2 | Softening Point | IS 1205 | 1 / 20 t | ≥ 47 °C |
| 3 | Ductility Test | IS 1208 | 1 / 20 t | ≥ 75 cm |
| 4 | Flash & Fire Point | IS 1209 | 1 / 20 t | > 220 °C |
| 5 | Marshall Stability & Flow | ASTM D6927 / IS 1201 | 1 / 400 t | Stability ≥ 9 kN; Flow 2–4 mm |
| 6 | Bitumen Content (Extraction) | IS 13826 | 1 / 400 t | ± 0.3 % of design |
| 7 | Field Density | MoRTH 507.3.7 | 1 / 250 m² | ≥ 98 % of lab density |
| 8 | Coating Uniformity | Field Inspection | Each batch | 100 % coated aggregates |
Recommended Plant Setup
| Equipment | Description |
|---|
| Hot Mix Plant (Batch Type) | Ensures precise temperature control and uniform coating of aggregates and plastic. |
| Shredding Machine | Cuts waste plastic into 2–4 mm flakes with consistent size for even melting. |
| Bitumen Sprayer | Applies tack coat uniformly before laying to promote bonding between layers. |
| Sensor Paver | Automatically controls level and slope for smooth riding surface. |
| Vibratory Roller | Provides the final compaction needed for density and surface finish. |
Design & Specification Notes
| Parameter | Recommendation |
|---|
| Bitumen Grade | Use VG-30 or VG-40 depending on climate; higher grades resist rutting in hot regions. |
| Plastic Type | Prefer LDPE (low-density polyethylene) because it melts uniformly and adheres well to aggregates. |
| Layer Type | Suitable for Bituminous Concrete (BC) and Semi-Dense Bituminous Concrete (SDBC) layers. |
| Max Plastic Content | Limit to 8 % by bitumen weight—excess causes brittleness and poor flexibility. |
Challenges & Field Observations
| Issue | Practical Solution |
|---|
| Overheating of plastic (black fumes) | Keep mixing temperature below 170 °C. |
| Uneven plastic distribution | Maintain consistent shred size and proper dry-mixing time. |
| Plastic storage problems | Store in a dry, covered area to avoid moisture contamination. |
| Coating difficulty on coarse aggregates | Use 10 – 20 mm aggregate size for best coating quality. |
Sustainability Impact
- Plastic Reused: ≈ 1 ton per km of road.
- Carbon Reduction: Up to 30 %.
- Extended Service Life: 1.5–2× longer than conventional bituminous pavements.
Relevant MoRTH Clauses
- Clause 507 – Dense Bituminous Macadam (DBM): Defines material, mix design, and compaction requirements ensuring durable binder courses for heavy traffic.
- Clause 509 – Bituminous Concrete (BC): Specifies binder content, gradation, and performance criteria for wearing courses.
- Clause 111 – Safety & Environmental Protection: Mandates pollution control, material handling, and worker safety measures on site.
- MoRTH Circular (2023): Updated national guidance on adopting plastic-modified bituminous mixes.
