Flexible pavements tend to become soft in summer & brittle in winter due to high temperature variation, also early development of distress symptoms occur due to heavy traffic loads on such roads, in these circumstances ordinary bitumen is not sufficient to overcome these symptoms.
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, reduced maintenance costs and excellent driving comfort.
Types of CRMB & Recommendation for specific use:
CRMB 60 : recommended for hot climate areas.
CRMB 55 : recommended for moderate climate areas.
CRMB 50 : recommended for cold climate areas.
Mixing/Coating 175-188 "C
Laying 150477 °C
Beginning off Compaction over I40 °C
End of Compaction 110420 "C
Advantages of CRMB:
- Lower susceptibility to daily & seasonal temperature variations.
- Higher resistance to deformation at elevated pavement temperatures.
- Better edge resistance properties.
- Better adhesion between aggregate & binder ensures longer life, strength and stability.
- Higher fatigue life of mixes due to high elastic recovery.
- Delay of cracking & reflective cracking.
- Overall improved performance in extreme climate conditions & under heavy traffic conditions.
- Better water resistance.
- Prevents rutting.
- Resistance to creep & higher indirect tensile strength.