Crumb Rubber Modified Bitumen
CRMB is a special type of bitumen whose properties have been improved by the addition of crumb rubber & special types of additives like hydrocarbon materials, resins etc. Thus altering the physical properties of bitumen making it more resistant to temperature variations, weather & high traffic loads, leading to enhanced pavement life, reduced maintenance costs and excellent driving comfort.
Types of CRMB & Recommendation for specific use:
- HARVIS CRMB 60: Recommended for hot climatic areas.
- HARVIS CRMB 55: Recommended for moderate climatic areas.
- HARVIS CRMB 50: Recommended for cold climatic areas.
| Mixing/Coating | 170-185 °C |
| Laying | 150-170 °C |
| Beginning of compaction | Over 140 °C |
| End of compaction | 110-120 °C |
Advantages of CRMB:
- Lower susceptibility to daily & seasonal temperature variations.
- Higher resistance to deformation at elevated pavement temperature.
- Better edge resistance properties.
- Better adhesion between aggregate & binder ensures longer life, strength & stability.
- Higher fatigue life of mixes due to high elastic recovery.
- Delay of cracking & reflective cracking.
- Overall improved performance in extreme climatic conditions & under heavy traffic conditions.
- Better water resistance.
- Prevents rutting.
- Resistance to creep & higher indirect tensile strength.
Applications:
CRMB can be used for wearing courses at heavily trafficked roads, busy intersections, bridge decks and roundabouts for increased life of the surfacing.
- Bus lane.
- Heavy trafficked lane.
- Slopes roundabouts junctions .
- Industrial and multimodal platforms.
- Airport runways and parking apron.
- Bus and trucks parking place.
- Providing high skid resistance (Thin overlay Chip Seal).
- Reducing traffic noise.
- Porous asphalt and acoustic thin overlay.
- Waterproofing Concrete structure.
- Sand asphalt.
- For snow bound regions.
- In Stress Absorbing Membrane Interlayer (SAMI).
- For high rainfall regions.
Specifications of CRMB (E) as per IRC SP 53-2002:
| Specification | CRMB 50 | CRMB 55 | CRMB 60 | Test Method |
|---|---|---|---|---|
| Penetration at 250°C | <70 | <60 | <50 | IS1203-1978 |
| Softening Point (R&B), C Min. | 50 | 55 | 60 | IS1205-1978 |
| Elastic Recovery of half thread in Flash Point, °C Min | 50 220 | 50 220 | 50 220 | IS15462-2004 IS1209-1978 |
| Separation difference in softening point, °C Max | 4 | 4 | 4 | IS15462-2004 |
| Thin Film Oven Test (TFOT) on Residue a. Penetration at 25°C, Min % of original b. Increase in softening point, °C, Max c. Elastic Recovery of half thread in Ductilometer at 25°C, % Min. | 60 7 35 | 60 6 35 | 60 5 35 | IS1205-1203 IS1205-1978 IS15462-2004 |
