The subject article is published in the February 2006 issue
of Indian Highways, a monthly journal of Indian Road Congress. The Author has
emphasized for the use of Cold mix technology in the construction of road
pavement, as it is more environmental friendly. He has described numbers of
available techniques of cold mix technology in the process.
In the hot mix technology, the aggregate and binder are
heated to specified temperature, mixed in desired proportion, transported to
the work site, placed, and compacted while the mix is still hot. In the cold
mix technology, the aggregate and binder are mixed, transported, placed, and
compacted in cold state.
Bituminous hot mix technologies create environmental
pollution by way of high emission, consume high amounts of energy and the mix
gets cooled during transportation from long distances leading to compaction
problems. It also has limitation for use in wet and low temperature conditions.
Because of air quality restrictions, the hot mix plants are also prohibited in
certain metropolitan areas.
The cold mix technologies, on the other hand, use
environmental friendly materials and techniques involving use of bitumen
emulsion, which can provide effective, energy efficient and long lasting
solutions. A number of techniques in cold mix have been developed and used
successfully.
Microsurfacing, uses a mixture of polymer-modified
emulsified bitumen (PEMB), dense-graded crushed mineral aggregates, mineral
filler, water and chemical additives to facilitate early setting of mix. PMEB
allows the material to remain stable when it is applied on the road surface.
This technology was originally developed in Germany in the late 1960s and
subsequently introduced to North America in the early 1980s.The material is
applied with specialized equipment that carries all the constituents, measures
accurately, mixes them , and spreads it over the road as homogeneous mix in
thin layers of 4-16mm thickness, depending upon the condition of the road. Experimental
stretches in Assam
and Delhi have been laid using this
technique and are under study by Central Road Research Institute of India.
Another technique in cold mix technology is
Cold-In-place-Recycling (CIR). Author says
that appropriate cold mix technology can be used on Indian Roads depending upon
the traffic volume and climatic conditions.