Rubberized asphalt concrete is
extremely useful for road construction projects since it is economical. It is
prepared from used tires that otherwise are delivered to the landfills and
occupy useful space. Rubberized Asphalt Concrete pavements include binders to
resist rutting.
Rubberized asphalt concrete is
basically used for road construction, and is obtained from recycled tires. It
is normally called RAC. It essentially includes ground tire rubber that is
obtained from the granulated rubber particles. During recycling, the rubber is
separated from the tire fabric and steel elements. The materials are grinded to
form crumb rubber. These materials are basically derived from tires of light
trucks or other resources where the content of rubber is high. RAC is produced
by the wet process that involves mixing of binder and the rubber. The binder
normally consists of 70%-80% of asphalt cement and 15%-25% of crumb rubber that
are mixed thoroughly before delivery to the hot mix plant. Studies have
established that four inch of the normal asphalt can be conveniently
substituted with two inches of rubberized asphalt, to attain similar fatigue
characteristics. This construction material has been proved to deliver
satisfactory performance. It is environmentally friendly and economical,
compared to the usual road paving materials. Normally, 2,000 used tires may be
consumed for each lane mile that is paved. In some countries, asphalt rubber is
one of the greatest single sources for ground rubber.
RAC has numerous advantages
due to which it is being extensively used globally. Some of the advantages are
explained below:
It is cost effective. A
2" thick RAC cover may save approximately $50,000 for each mile compared
to a 4" normal asphalt overlay.
It is durable, and resistant
to cracking. Use of these materials has established that suitably designed RAC
have a considerably longer life compared to the normal materials. The
maintenance expenditure is reduced significantly.
RAC is environmental friendly.
A 2" resurfacing may consume more than 2,000 scrap tires for each lane
mile. This implies that a one mile segment of a four lane road, will consume
more than 8,000 scrap tires. Thus, a huge number of scrap tires will be
excluded from being dispatched to the landfills. States are vigorously
redirecting the used tires from the public landfills, for use on highways, by
combination of old tires rubber with asphalt. Waste tires are a serious health
hazard, due to creation of shelters for mosquitoes and rodents.
The road noise may be reduced
up to 80%
RAC can maintain its
initial color better than the usual
asphalt, and the markings continue to be clearer.
The traction provded by these materials is better that facilitate
in the reduction of road accidents, especially in poor weather.
RAC may not be used for all
road applications. These materials are not suitable for road application during
extreme cold or hot weather. Paving problems have been experienced during such
temperatures. Temperature influences the placing and compacting of normal
mixtures. Placing of these materials is not suitable during the following
conditions:
During wet weather.
During chilly conditions with
the ambient temperatures are less than 15°C.
Over the existing pavements
with critical distortions.