NHAI, CRRI trial 60% reclaimed bitumen on Chennai-Tirupathi highway stretch

A one-kilometre stretch of the access-controlled Chennai-Tirupathi National Highway, currently under widening, has been laid using a mix that contains 60% reclaimed asphalt pavement. The material was milled from the old road and rejuvenated with a special additive developed by the CSIR-Central Road Research Institute (CSIR-CRRI).

The top bituminous layer of aged roads loses elasticity over time. CSIR-CRRI's additive, when added to cold-milled material, restores its strength for reuse in fresh road construction, according to Chalumuri Ravi Sekhar, Director of CSIR-CRRI.

Though the technology was developed two years ago, earlier trials were limited to small patches. Now, CSIR-CRRI has transferred the technology to Ooms Polymer Modified Bitumen Pvt Ltd for commercial production. The company, along with Oriental Structural Engineers Private Limited (the road-widening contractor), partnered with the National Highways Authority of India (NHAI) to conduct this field demonstration.

Currently, the Indian Roads Congress (IRC) code permits reusing up to 30% reclaimed bitumen in road relaying. This advancement allows doubling that proportion, keeping material that would otherwise be sent to dump yards. Ravi Shankar, Senior Scientist at CSIR-CRRI, noted that recycling bitumen could reduce dependence on foreign exchange in the long run. The results will be submitted to the IRC, which may update its code accordingly.

The core team behind the additive includes Ambika Behl, Rajiv Kumar, and Siksha Swaroopa Kar, all senior scientists at CSIR-CRRI. Recently, institute scientists visited the Tiruvallur site to verify that the methodology and procedures were correctly applied.

Venkatachalam, Director of the Highways Research Station, said Tamil Nadu has been reusing 30% bitumen wherever possible. He added that the 60% utilisation opens up interesting possibilities, but the state will wait for the IRC code to be updated before adopting it.