For the construction of roads in India, hot mixes prepared at a temperature of 1550C are conventionally used. It causes air pollution due to the emission of hydrocarbon and suspended particulate matters and consumes higher energy. Emulsion based cold mixes offer a potential solution of the above drawbacks due to elimination of heating process. In this technology, cold mixes are prepared by mixing aggregates with bitumen emulsion at ambient temperature. Bitumen emulsion based cold mix offer certain advantages over hot bituminous road mixtures in terms of potential cost savings, protection of environment, energy savings, decrease in carbon footprint, use of damp aggregates and increase in construction period during the year as construction with cold mix is feasible in cold climate, rainy seasons and even during monsoon seasons with wet aggregates. The use of emulsion based cold mix provides green technology for road construction as it eliminates heating. This method can also be adopted in forest areas, since the conventional method is not allowed there.
The first trial in Kerala was conducted on 17th March 2016 by the Local Self Government Department in ‘Vengodu Cheroor Road at Pothencode’ under LSGD Sub Division, Pothencode. It was carried out under the guidance of the Chief Engineer, Sri. P.R. Sajikumar and the Executive Engineer, Sri S. Anwar Hussain. The other team members are Smt. Ganga R.S., Assistant Executive Engineer, Sri. Shiju Chandran R., Assistant Engineer, Sri. Krishnakumar, 1st grade Overseer and the contractor of the work,Sri. Hary Austin. The trial was assisted by the technical team of M/s Hindustan Colas (HINCOL), Dr. N.K.S. Pundhir, Sri. Subin Punnoose, Sri. K.G. Ranganatha, Sri. K. Siva Kumar and Sri. Arun P M.
The trial reach was of 100 m damaged bituminous surface, over which the premix chipping carpet with seal coat was laid using bitumen emulsion instead of normal bitumen. The cold mix was prepared in a concrete mixer in lieu of the hot mix plant with 13.2 mm and 11.2 mm locally available aggregates in 2:1 ratio and premix MS emulsion. The blended aggregates were charged in the mixer and 1% water was added to damp the aggregates. Then a quantity of 6% emulsion (MS) by weight of aggregates was added into the mixer having damp aggregates to prepare the cold mix. The cold mix was discharged into pickup auto rickshaw to ferry the cold mix to the construction site. The laying of Pre Mix Carpet (PMC) was done manually by spreading cold mix on tack coated existing road. After 20 minutes, the tack coat emulsion changed to black from brown colour. After that, compaction with 8- 10 tonnes roller was provided to get PMC. Then seal coat was carried out on PMC to fill the voids. The construction of the trial stretch was completed within a day. After completing the construction, the road shows a good finishing and it feels harder than the conventional mix. It was opened to traffic after 1 hour.
The departmental officials feel that this technology is eco-friendly and it can be used for rural roads effectively after evaluating its performance. This technology can be used for new roads also. The workers also lauded this technology saying that it is not only eco-friendly but also friendly to them. In future, they will not have to deal with heated materials. The company claims that it is economical also, since the construction with cold mix is cheaper than the conventional method by 15 to 20%.