Stone matrix asphalt (SMA) is a gap-graded Hot Mix Asphalt, that is designed to maximize deformation (rutting) resistance and durability ,by using a structural basis of stone-on-stone contact. Because the aggregates are all in contact, rut resistance relies on aggregate properties rather than asphalt binder properties. Since aggregates do not deform as much as asphalt binder under load, this stone-on-stone contact greatly reduces rutting. SMA requires adherence to specifications to be successful, Quality of Aggregates, Quality of Bitumen and Mix Design as per specification are the primary parameters all implementing authorities need to be aware of.

There are several mixture design factors that must be met. Among these are:

• Provide stone-on-stone contact through the selection of the proper gradation,
• Use hard, cubical, durable aggregate,
• Design at an asphalt content of at least 6 percent and air void content of 4 percent, for most mixtures,
• Check for and meet moisture susceptibility and draindown requirements.

There are also several good production and construction practices that should be followed:

• Maintain close control of plant stockpiles and cold feed,
• Maintain close control of plant temperature,
• Maintain a consistent paving speed and compaction effort,
• Use the necessary number of rollers to achieve a minimum density of 94 percent of maximum density,
• Avoid manual work whenever possible,
• Minimize the number and size of fat spots that appear behind the paver,
• Use good quality assurance practices including frequent monitoring of all aspects of production, paving, and compaction.

Advantages of SMA

The primary advantage of SMA is the extended life with improved pavement performance compared to conventional dense-graded hot-mix asphalt (HMA). The other advantages are noise reduction, improved frictional resistance, and improved visibility.

Four steps are required to obtain a satisfactory SMA mixture are:

• select proper aggregate materials,
• determine an aggregate gradation yielding stone-on-stone contact,
• choose an asphalt content that provides the desired air void level, and
• evaluate the moisture susceptibility and evaluate the moisture susceptibility and asphalt cement draindown sensitivity.

While adhering the above one has to take into consideration the use of Cellulose Fibers as a Drainage Inhibitor dosed at 0.3% of the total mix. SMA being new in India there are many misconceptions about usage of these fibers. A misconception that Imported fibers perform better then Indian fibers is most common . We have practically implemented the use of both Fibers in SMA Imported as well as Indian. And we can conclude that Indian Fibers are of same quality as imported ones , performance of the Indian Fibers is as good as Imported Fibers.

We Genesis Infra Project Consultant, have been implementing consultants for many SMA projects across India. With our experience and knowledge we can assure Indian fibers perform as required in SMA.

We would be pleased to answer queries as well as assist as consultants for implementing SMA successfully using Indian Cellulose Fibers. Feel free to connect to us on genesisinfraconsultants@gmail.com or contact@genesisinfraconsultants.com also visit www.genesisinfraconsultants.com/