This document discusses different types of modified bituminous materials used in pavement construction including polymer modified bitumen, bitumen rubber mixes, stone matrix asphalt, and warm mix asphalt. It provides details on the composition and properties of these materials. Polymer modified bitumen involves adding polymers like SBS or EVA to bitumen to improve its high temperature stability and resistance to deformation. Stone matrix asphalt contains a high percentage of coarse aggregate that forms an interlocking skeleton structure, filled with bitumen and filler, to provide durability and resist permanent deformation on heavily trafficked roads.

1. • POLIMER MODIFIED BITUMEN
• BITUMEN RUBBER MIXES
• STONE MATRIX ASPHALT
• WARM MIX ASPHALT

2. Pavement Composition
Asphalt/ Bitumen
Bitumen Materials Used in India
Polymer Modified Bitumen
Bitumen Rubber Mixes
Stone Matrix Asphalt
Warm Mix Asphalt

3. Pavement
Composition
Sub-base Base Surface

4. Asphalt, also known as bitumen, is a sticky,
black and highly viscous liquid or semi-solid
form of petroleum. It may be found in natural
deposits or may be a refined product ; it is a
substance classed as a pitch.
Pitch is a name for any of a number
of viscoelastic-solid polymers. Pitch can be
natural or manufactured, derived
from petroleum, coal tar or plants. Various forms
of pitch may also be called tar, bitumen
or asphalt.

7. OPEN GRADED MIXES:
o Bituminous Macadam (BM)
o Semi Dense Bituminous Concrete (SDBC)
o Dense Bituminous Macadam (DBM) Grading 1
DENSE GRADED MIXES:
o Dense Bituminous Macadam (DBM) Grading 2
o Bituminous Concrete (BC) Grading 1
o Bituminous Concrete (BC) Grading 2

8. Polymer Modified Bitumen (PMB)
Natural Rubber Modified Bitumen (NRMB)
Crumb Rubber Modified Bitumen (CRMB)
Stone Matrix Asphalt (SMA)
Warm Mix Asphalt (WMA)
 PMB, NRMB, CRMB for high traffic roads.
SMA for very heavy-trafficked roads with
overloading.
VG-30 Bitumen is normally used nowadays.

9. Modified bituminous materials can bring real
benefits to highway maintenance/construction,
in terms of better and longer lasting roads, and
savings in total road life cost.
But the choice of what materials to choose and
how they perform has to be said is a bit of a
minefield at present with little truly
independent advice available, and this guide
may help in making the necessary decisions.

10. A polymer is a large molecule,
or macromolecule, composed of many repeated
subunits. Because of their broad range of
properties, both synthetic and natural polymers
play an essential and ubiquitous role in everyday
life. Polymers range from familiar
synthetic plastics such as polystyrene to
natural biopolymers such
as DNA and proteins that are fundamental to
biological structure and function.

11. SYNTHETIC POLYMERS
These are polymers that have been manufactured in a
chemical process to combine particular molecules in a
way that would not occur naturally.
And although various synthetic polymers have been
capable of being produced since the early part of this
century it is the more recently developed polymers
that are now being used to modify bitumens and
produce the "new" bituminous binders.
The new polymers being the result of research and
development by the large petro-chemical industries.

12. NATURAL RUBBER
Rubberised asphalt, mainly surface course
(wearing course) but also binder course
(basecourse), has been used with a fair degree
of success for over 40 years.
Rubber is a natural polymer and its action in a
bituminous mix is similar to that of the
synthetic thermoplastic rubbers (TR's).

13. Bitumen is so useful in the road making and road
maintenance industries because of its basic thermoplastic
nature, i.e. it is stiff/solid when cold and liquid when hot,
(well with penetration grade bitumens anyway).
(The modifying polymers used in bitumen are also
thermoplastic in nature.)
The basic properties of bitumen can be modified by the
addition of flux oils or volatile oils to produce bitumen of
various grades.
These grades are specified by their viscosity, (penetration),
and their softening point, this information, along with other
physical characteristics is specified in.

15. Polymers change the physical nature of
bitumen, and they are able to modify physical
properties such as the softening point and the
brittleness of the bitumen.
Elastic recovery/ductility can also be
improved.

16. Thermoplastic Rubbers, (TR's)
This may be regarded as a group name /
description for a number of polymers/copolymers
used in the modification of bitumen.
A copolymer is a polymer that has more than one
type of molecule incorporated in the polymer.
These polymers are made up of many thousands
of individual monomers/molecules built up into
chains by the various polymerisation processes
developed by the large chemical industries.

17. Styrene Butadiene Styrene, (SBS)
This is a thermoplastic rubber.
SBS is a copolymer that you will come across
in bitumen modification, it was originally
developed for use in the production of tyres
and the soles of shoes, but is suitable for the
modification of bitumen.

18. Natural Rubber Modified Bitumen (NRMB) :
using latex or rubber powder.
Crumb Rubber Modified Bitumen (CRMB) :
using crumb rubber powder from discarded
truck tires further improved by additives.
Polymer Modified Bitumen (PMB) : using
polymers like Ethylene Vinyl Acetate (EVA)
or Styrene Butadiene Styrene(SBS) etc.

19. Polymer, typically in either crumb, pellet or
powder form is added to hot asphalt which
penetrates the polymer particles and causes
them to swell and flow.

20. Improved aggregate adhesion in highly
stressed areas.
Superior load carrying capacity for a given
thickness compared to conventional bitumen.
Higher cohesive strength to withstand
stripping action of high speed traffic.
Higher viscosity at elevated temperatures
combats bleeding of binder.

21. Lower susceptibility to temperature variations.
Higher resistance to deformation at elevated
pavement temperature.
Better age resistance properties.
Higher fatigue life of mixes.
Overall improved performance in extreme
climatic conditions.
Reduction in overall life cycle cost of overlays.
Higher stiffness modulus.
Better resistance to creep.

25. Stone-matrix asphalt was developed in
Germany in the 1960s.
It provides a deformation resistant, durable
surfacing material, suitable for heavily
trafficked roads.
SMA has found use in Europe, Australia, the
United States, and Canada as a
durable asphalt surfacing option for residential
streets and highways.

26. SMA has a high coarse aggregate content that
interlocks to form a stone skeleton that resists
permanent deformation.
The stone skeleton is filled with
a mastic of bitumen and filler to which fibers are
added to provide adequate stability of bitumen
and to prevent drainage of binder during
transport and placement.
Typical SMA composition consists of 70−80%
coarse aggregate, 8−12% filler, 6.0−7.0% binder,
and 0.3 per cent fiber.

28. The deformation resistant capacity of SMA
stems from a coarse stone skeleton providing
more stone-on-stone contact than with
conventional dense graded asphalt (DGA) mixes
(see above picture).
Improved binder durability is a result of higher
bitumen content, a thicker bitumen film, and
lower air voids content. This high bitumen
content also improves flexibility.
Addition of a small quantity of cellulose or
mineral fiber prevents drainage of bitumen
during transport and placement.

30. SMA is mixed and placed in the same plant as that
used with conventional hot mix. In batch plants, the
fiber additive is added direct to the pug mill using
individually wrapped press packs or bulk dispensing
equipment.
Mixing times may be extended ensure that fiber
is homogeneously distributed throughout the mix and
temperatures controlled in order to avoid overheating
or damage to the fiber.
In drum plants, particular care must be taken to
ensure that both the additional filler content and fiber
additive are incorporated into the mixture without
excessive losses through the dust extraction system.

31. Filler systems that add filler directly into the
drum rather than aggregate feed are
preferred.
Pelletized fibers may be added through
systems designed for addition of recycled
materials, but a more effective means is
addition through a special delivery line that is
combined with the bitumen delivery, so that
the fiber is captured by bitumen at the point
of addition to the mixture.

32. The primary difference in placing SMA, compared to DGA
is in compaction procedures.
Multi-tyre rollers are not used due to the possible working
of binder-rich material to the surface of the asphalt and
consequent flushing and pick-up.
Trafficking of the newly placed asphalt while still warm
may have the same effect and it is generally preferable for
surfaces to cool below about 40°C before opening to traffic.
The preferred method of compaction is to use heavy, non-vibrating,
steel-wheeled rollers. If these are not available,
vibrating rollers may be used but vibration should be kept
to a minimum to avoid fracture of coarse aggregate
particles, or drawing of binder to the surface of the mix.

33. The use of polymer modified binder may decrease
mix workability and necessitate increased compactive
effort to achieve high standards of compacted density.
Achieving high standards of compacted density and
low field air voids has been identified as an important
factor in the performance of all SMA work.
SMA is normally placed with a minimum layer
thickness of 2.5 to 3 times the nominal maximum
aggregate particle size. Greater layer thicknesses assist
in achieving appropriate standards of compacted
density.

34. Aggregates used in SMA must be of high quality – well shaped,
resistant to crushing and of suitable polish resistance.
Binders used in SMA include:
Class 320 bitumen - used in many general applications.
Multi grade binder - used to provide enhanced performance at
higher traffic levels.
Polymer modified binder - increasingly used in heavy traffic
conditions to provide additional resistance to flushing
and rutting.
Cellulose fiber is most commonly used in SMA work in
Australia. Other fibre types, including glass fiber, rock
wool, polyester, and even natural wool, have all been found to
be suitable but cellulose fiber is generally the most cost-effective.
Fiber content is generally 0.3% (by mass) of the
total mix.

35. SMA provides a textured, durable, and rut resistant wearing
course.
The surface texture characteristics of SMA are similar to
Open graded asphalt (OGA) so that the noise generated by
traffic is lower than that on DGA but equal to or slightly
higher than OGA.
SMA can be produced and compacted with the same plant
and equipment available for normal hot mix, using the above
procedure modifications.
SMA may be used at intersections and other high traffic
stress situations where OGA is unsuitable.
SMA surfacing may provide reduced reflection cracking from
underlying cracked pavements due to the flexible mastic.
The durability of SMA should be equal, or greater than, DGA
and significantly greater than OGA.

36. Increased material cost associated with higher asphalt
binder and filler contents, and fibre additive.
Increased mixing time and time taken to add extra
filler, may result in reduced productivity.
Possible delays in opening to traffic as the SMA mix
should be cooled to 40°C to prevent flushing of the
binder to the surface (bleeding).
Initial skid resistance (lack of Friction) may be low
until the thick binder film is worn off the top of the
surface by traffic. In critical situations, a small, clean
grit, may need to be applied before opening to traffic.

38. Warm-Mix Asphalt was developed in Europe
in response to EEC countries signing the 1997
Kyoto Treaty to reduce greenhouse gases.
Warm mix asphalt concrete (commonly abbreviated
as WMA) is produced by adding zeolites, waxes,
asphalt emulsions, or sometimes even water to the
asphalt binder prior to mixing.
This allows significantly lower mixing and laying
temperatures and results in lower consumption
of fossil fuels, thus releasing less carbon
dioxide, aerosols and vapors.

39. Not only are working conditions improved,
but the lower laying-temperature also leads to
more rapid availability of the surface for use,
which is important for construction sites with
critical time schedules.
The usage of these additives in hot mixed
asphalt (above) may afford easier compaction
and allow cold weather paving or longer hauls.

41. Reduces Plant Fuel Consumption – Studies have
shown that running your plant at 35° F – 100° F lower
will reduce fuel consumption by an average of 15%.
Reduces VOC Stack Emissions – The EPA has found
that volatile organic compounds (VOC) released
through the stack of an asphalt plant are well within
required EPA guidelines. The use of WMA has been
shown to reduce these emissions between 50-90%.
Easy to Compact. WMA has been found to be easier
to compact, especially very stiff mix designs. Some
contractors have eliminated a roller from the paving
train. This saves money, time and energy resources.

42. Increased RAP Usage – The reduced viscosity of the WMA
allows for easier coverage of the RAP and because the asphalt
cement is not being aged at higher temperatures, the virgin
asphalt binder may help to rejuvenate the inherent binder of
the RAP. The increased use of RAP is a savings to contractors,
agencies, and creates sustainable pavements by reducing the
need for petroleum and virgin aggregates.
Fume and Smell Reduction – The largest source of
emissions from an asphalt plant is the result of fuel
combustion during the drying and heating process. The
decrease in fuel consumption is directly correlated to reducing
these emissions. In addition, reducing temperature at load out
and paving has a direct correlation to fumes at the plant and
asphalt pavers.

43. Better Work Environment – The reduction in
temperature behind the paver makes a more
comfortable environment for employees and
government workers.
Reduces “Aging” Asphalt Cement – The
heating of asphalt cement oxidizes the material
for every 25° F it is heated.2 By decreasing the
temperature needed to produce WMA we may be
decreasing the “aging” of the asphalt binder and
thereby creating longer lasting pavements.