Adopting Stone Matrix Asphalt is one way to make highways durable and sustainable.

Sanjeev Goel

- Founder & MD, Descon Infrastructures

Descon Infrastructures has been active promoter of road safety for the last 25 years. In the 25 years of its existence, Descon Infrastructures has grown into an urban infrastructure development firm with focus in both highway & building infrastructure. Descon has significantly strengthened its core infrastructure business verticals. With the introduction of stone matrix asphalt, advanced road laying solution the company aims at providing better quality of highway infrastructure. Sanjeev Goel, Founder & MD & Pranjal Goel, Executive Director, Descon Infrastructures talks about the scope and potential of SMA technology….Excerpts from the interview…

Could you brief us on the concept behind SMA and how critical is the use of polymer modified bitumen courses in constructing durable and sustainable roads & highways?

Surface transport has increased significantly over the years. Conventional design mix's showcase limitations and need repetitive maintenance at an average of 3-4 years. Stone Mastic Asphalt or more popularly known as SMA provides a long term solution. SMA is a gap graded mix with a higher percentage of both aggregates & binder rich mortar. Since bitumen is liable to bleeding or leaching, bitumen coated cellulose are used in the hot mix. The cellulose fibers ensure that the bitumen doesn't bleed or leach, thereby ensuring a durable and long-lasting pavement. This is also the very reason why pavements designed on the SMA technology show almost no signs of rutting.

The volume of heavy-duty traffic has been on the rise over the recent years. Pavements designed and constructed for heavy-duty traffic and extreme weather conditions require specially designed engineered Bitumen Grades. When a polymer is added to regular bitumen, it becomes more elastomeric, which provides it with additional elasticity. By changing the characteristics of normal bitumen with the addition of a polymer, the mixture becomes more cohesive, with much more strength and significant higher resistance to parameters like fatigue and permanent deformations for road pavements.

How sustainable and eco-friendly is SMA technology and what is the bearing of SMA technology on the mix design, and construction process like compaction and paving etc? 

SMA mix prime technical advantage is its ability to prolong the life of the pavement to 12 - 15 years without the need for resurfacing or other maintenance measures. Conventional design mix on the other hand require resurfacing/ maintenance of the wearing course between every 2nd or 3rd year. This particular attribute reduces the requirement for natural resources i.e., aggregates, fuel & bitumen, etc. Given that there are only a finite number of resources on this planet, adopting SMA is one way to make highways durable and sustainable.

The design mix for SMA varies significantly than the conventional mix. SMA mix usually requires more coarse aggregate, 11-12% & 3-4% higher volumes of bitumen and fillers respectively. The processing mechanism on the other hand, i.e. compaction or paving are carried out in the same manner as for a conventional BC mix.

Compared to the conventional dense-graded mix what are the superior features of SMA?

• Rutting resistance
• Crack resistance
• Higher fatigue limit
• Impermeability
• Long term economic effectiveness

What are the techno-commercial benefits?

The initial investment though slightly more than a conventional gap graded mix but over its lifecycle, SMA proves to be highly cost efficient. A conventional mix may be subjected to renewal between every 3rdto 5th year. Whereas with SMA, with the high durability and other superior features imparted to the pavement, no renewal costs may be incurred before 12 to 15 years.

How do you rate the success of this technology in the national / state highways so far?  What are the hurdles in faster adoption of SMA in highway projects? 

Although a few national highways & state highways have been delivered with SMA over the last 10 years, it is yet to write its success story in India, At the policy level, the fifth revision of the Specifications of the Road & Bridge Works (Section 515), has already incorporated the SMA design mix. Howevertill date there is no cross linkage of SMA design parameters in the Indian Road Congress Design Code (IRC:37).Central Road Research Institute (CRRI), the premier institute on road research in India, recommends the use of SMA technology even for city roads. At present, two of the expressways being constructed by the NHAI have adopted the SMA technology.

Could you name some of the road projects where SMA technologies have been used? 

PalanpurDisa (NH 14) - 5 kms

Kishangarh Ajmer Beawar (NH 8) - 20 kms

BijapurHungund (NH 13) - 2kms

MayurVihar Toll Plaza - 6 kms

Chhindwara Nagpur (NH 69A) - 10 kms

Piramal Underpass, Ahemdabad - SMA laid over existing rigid pavement

How do you assess the future prospects?

The Ministry of Road Transport & Highways (MoRTH) is keen on adopting new technologies for the future developments. In the last few years, the pace of highway construction in India has exceeded all records. With the above in mind, it is fair to be optimistic about the future of SMA.

Brief us on the solution offered for road safety?

Road safety solutions vary vastly depending on the classification of the road. The government has actively taken up the agenda of addressing several black spots on any road. A black spot
by definition is the stretch on a street where either 5 road accidents involving fatalities and grievous injuries have happened in the last 3 calendar years or 10 fatalities during the last three years. The first and foremost measure in addressing road safety is road markings. Road markings provide guidance to any vehicle by outlaying the route ahead. Retro reflective signage are the second measure which inform the driver of the conditions ahead. Metal beam crash barrier are another measure which in the event of an accident ensure that no vehicle leaves the right of way, thereby reducing the chances of a fatality.

What is the core strength and competencies of Descon Infra? Please also brief us on your road map for next couple of years?

Descon Infrastructures has been active promoter of road safety for the last 25 years.
Our sister concern, Acmetech Consultants is a certified road safety auditing firm. This allows us to offer technical assistance in a professional manner. We are committed to delivering sustainable solutions and therefore lay great emphasis on the quality of products leaving our manufacturing unit.

Over the years to follow, Descon Infrastructures envisions to venture into core infrastructure development. Our vision 'Design & Construction - to enrich the quality of the infrastructure ecosystem with smart, safe and integrated solutions' has been crafted keeping in mind the same.

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