Step-by-Step Process of Using Waste Plastic in Bituminous Mix (MoRTH 2025)

    The use of waste plastic in bituminous mix is an innovative and sustainable method recognized by the Ministry of Road Transport and Highways (MoRTH) and Indian Roads Congress (IRC:SP:98-2013). The process improves the binding property of bitumen, enhances the road’s durability, and supports India’s goal of plastic waste reduction.

    Reference: MoRTH Circular No. RW/NH-33041/20/2016-S&R(R) Pt. III – Guidelines for Use of Waste Plastic in Hot Bituminous Mixes.

    Step 1 – Collection and Segregation

    Collect non-recyclable plastic waste such as carry bags, cups, wrappers, and packaging films. Ensure materials are clean, dry, and free from PVC or PET, as these can emit toxic fumes on heating.

    • Preferred types: LDPE, HDPE, and PP
    • Reject types: PVC, PET, Thermosetting plastics
    • Moisture content: Below 1%

    Step 2 – Shredding of Plastic Waste

    Shred the cleaned plastic into small flakes of 2–4 mm size using a mechanical shredder. This ensures uniform melting and coating during mixing with aggregates.

    Tip: Use a rotary-blade shredder with sieve control for consistent flake size and avoid blockages in the hot mix plant feeder.

    Step 3 – Heating of Aggregates

    Heat the aggregates in the drying drum of the hot mix plant to a temperature between 150–160°C. The moisture content must be completely removed to ensure proper plastic adhesion.

    Step 4 – Mixing of Shredded Plastic (Dry Process)

    1. Feed the hot aggregates into the mixing drum.
    2. Add shredded plastic waste in the dry-mix zone (before bitumen injection).
    3. Mix for 30–40 seconds until the plastic melts and coats the aggregate surface uniformly.

    Observe the aggregates — a glossy surface appearance indicates proper coating.

    Step 5 – Addition of Bitumen

    • Heat bitumen separately to 160–170°C.
    • Add it to the plastic-coated aggregates.
    • Continue mixing for 45–60 seconds to ensure full homogenization.
    Plastic Content: 6–8% by weight of bitumen (optimum). Excess may cause brittleness.

    Step 6 – Laying and Compaction

    • Maintain mix temperature at 130–140°C during transportation.
    • Use a sensor paver for accurate level and slope control.
    • Compact using tandem and pneumatic rollers to achieve ≥98% of laboratory density as per MoRTH Clause 507.3.7.

    Step 7. Quality Control Checklist (MoRTH & IS Codes)

    S. NoTest NameReferenceFrequencyAcceptance Criteria
    1Penetration TestIS 12031 / 20 t60–80 mm (VG-30)
    2Softening PointIS 12051 / 20 t≥ 47 °C
    3Ductility TestIS 12081 / 20 t≥ 75 cm
    4Marshall Stability & FlowASTM D6927 / IS 12011 / 400 tStability ≥ 9 kN; Flow 2–4 mm
    5Field DensityMoRTH 507.3.71 / 250 m²≥ 98 % of lab density

    Step 8. Safety & Environmental Considerations

    • Ensure adequate ventilation around the mixing area.
    • Workers should wear masks, gloves, and safety shoes.
    • Avoid overheating plastic beyond 170°C to prevent emission of fumes.

    Step 9. Advantages of the Dry Process

    • Simple to implement using existing batch-type HMPs.
    • No chemical blending equipment required.
    • Ensures uniform coating and better stability values.

    FAQs – Field Methodology for Plastic Mix

    Q1: Which plastic is preferred for bituminous mix?
    Low-density polyethylene (LDPE) because it melts uniformly and forms strong coating on aggregates.

    Q2: How much plastic should be added?
    6–8% by weight of bitumen.

    Q3: What temperature should be maintained during mixing?
    Aggregates: 150–160°C; Bitumen: 160–170°C.

    Q4: Can this method be used for DBM and BC layers?
    Yes. It is approved for Dense Bituminous Macadam (Clause 507) and Bituminous Concrete (Clause 509).

    Also Read:

    📥 Download: Field Checklist for Plastic Modified Bituminous Mix (MoRTH 2025)

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