Specification for Bituminous Concrete (Asphaltic Concrete) for Road Pavement (First Revision)
1988 الطبعة

IRC 29 stipulates that coarse aggregates should have maximum limits such as Aggregate Impact Value between 30-40%, Los Angeles Abrasion or Flakiness Index up to 25%, Stripping Value not exceeding 25%, and Water Absorption limited to 1% (with up to 2% allowed in special cases). Soundness losses are capped at 12% for sodium sulphate and 18% for magnesium sulphate tests. Crushed slag must be air-cooled blast furnace slag with specific unit weight and composition limits including a maximum of 20% glossy particles and 6% flat or elongated pieces. Fine aggregates are required to pass the 2.36 mm sieve and be retained on the 75 µm sieve, consisting of clean, hard, durable particles free from harmful substances. Filler material must be inert and pass the 600 µm sieve, with at least 90% passing the 150 µm and 70% passing the 75 µm sieves.

Detailed information on binder content determination is not provided in the available data.

Recommended procedures include avoiding work during adverse weather conditions such as rain, fog, or temperatures below 10°C. The base surface must be properly shaped, cleaned, and free of dust. A tack coat of low viscosity bitumen is uniformly applied using a pressure sprayer at rates dependent on the surface type. Mix preparation requires hot mix plants maintaining aggregate temperatures between 153°C to 163°C and binder temperatures from 150°C to 177°C, ensuring thorough coating and mixing. Transport of mix should be in clean, covered vehicles when necessary. Spreading is performed using self-propelled mechanical pavers with screeds for uniform thickness, with manual methods reserved for limited cases. Compaction is carried out immediately after spreading using a sequence of rollers—breakdown, intermediate pneumatic, and finishing rollers—maintaining speeds not exceeding 5 km/h with moist but not oily roller wheels. Traffic should only be allowed after final rolling is complete and the mix has cooled to ambient temperature.

Quality control involves periodic sieve analyses at the cold feed to verify aggregate gradation adherence to the job mix formula, testing aggregate physical properties like Aggregate Impact Value, Los Angeles Abrasion, Flakiness Index, Stripping Value, and Water Absorption following relevant IS standards. Binder and aggregate temperatures must be monitored to remain within specified limits, with a maximum temperature difference of 14°C during mixing. Uniform coating and homogeneity of the mix are ensured through proper plant operation and mixing procedures. Actual aggregate gradation variations are controlled within permissible limits defined in the job mix formula. Tack coat application rates are checked as per the designated surface type requirements. Compaction must achieve a density of at least 98% of the laboratory Marshall specimen and eliminate roller marks to ensure pavement quality.

Traffic can be permitted only after the final rolling has been completed and the bituminous concrete has cooled to the ambient temperature. This ensures the pavement has attained adequate compaction and stability to resist damage from traffic loads.