A modern Asphalt Multi
Integrated Roller has been introduced for road construction that assists in the
prevention of asphalt cracks that are developed by the use of conventional
steel rollers.
Compaction of an asphalt mix
has been a standard in the building and functioning of the pavements for a long
period. It has commonly been assumed that the results of compaction lie in the
ensuing density and air voids,and are
not due to construction techniques. It has also been considered that the cracks
induced by construction only appear unattractive and do not actually affect the
physical performance of the surfacing.
Extensive research has been
conducted to establish the real cause and effect of the construction cracks. It
was established that compaction by steel roller is responsible for
construction-induced cracks due to the geometric unsuitability between the
roller and the base. Damage and cracks in roads are not only due to cold
weather because these issues have also been observed on roads in countries with
warm weather.
The AMIR has a belt with
multiple layers that are made of specific rubber compounds.The belt
and rollers create plate-like contact surface of approximately three square
meters to use for compaction. The rubber belt, being elastic, provides a
surface that is similar in stiffness to the asphalt surface. Since the contact
area available is large due to the flat plate, the applied stress at the
asphalt is insignificant compared to that applied by conventional steel
rollers. Furthermore, if the rolling speed is same, the load duration by AMIR
is thirty times greater than normal steel rollers. The huge contact area
reduces horizontal forces applied to the asphalt and ensures confinement during
the compaction. Thus, the roller induced cracking is eliminated, permeability
is reduced, and resistance to fatigue damage and tensile strength are increased.
AMIR has overcome compaction
problems and produces a smooth surface that does not have cracks. Numerous
fatigue tests were performed on different mixes. Comparison was carried out of
the compaction produced by the normal rollers and the Asphalt Multi Integrated
Roller. The contributing factors like direction and kind of mix were varied to
obtain results under different test conditions. The test results demonstrated
that compaction by the Asphalt Multi Integrated Roller, using either form of
mix, produced approximately twice the compaction fatigue life. It was also
observed that the rolling direction had an insignificant effect on the fatigue
life of the mix produced by Asphalt Multi Integrated Roller. However, the
fatigue resistance to transverse cracking was low for the mix produced by steel
rollers. The research has concluded that the cracks produced by steel rollers
can decrease the fatigue life considerably, and these problems can be overcome
by the use of Asphalt Multi Integrated Roller. Furthermore, the mechanical
properties like density, fatigue life, tensile strength and moisture resistance
are improved considerably.
Cracks produced during
compaction by normal steel rollers are due to the non
harmony of the rigid circular steel drum with the gentle, even
asphalt pavement. Since the shape of the steel drums is circular, only a small
contact area is accessible to the asphalt for compacting. With the movement of
the roller, the asphalt at the roller front is pushed forward, producing a
dragging force in the asphalt at the rear. This action of pushing and dragging
produces cracks in the asphalt. The rollers with rubber tires were introduced
to press the asphalt and seal the cracks. However, such rollers have not been
successful to prevent the development of cracks. Furthermore, these rollers use
water to avoid picking asphalt during the compaction. This lowers the
temperature of the asphalt and avoids the crack closing.