Important Asphalt Related Issues in India
“American roads are good not because America
is rich, but America
is rich because American roads are good.” - John F. Kennedy
“Never doubt that a small group of citizens can change the
world. Indeed, it is the only thing that ever has.” -
Margaret Mead
“To improve is to
change; to be perfect is to change often.”
- Winston Churchill
There are several important asphalt-related issues in India ,
which need to be addressed and/or implemented by the government, contractors
and consultants to ensure durable asphalt pavements without any premature
distress and potholes. A detailed discussion of the following issues follows.
- Why
roads in
- Potholes,
potholes and more potholes in
3. Why the NHAI is burying bitumen worth hundreds
of crores rupees under national highways?
- Are
we really getting viscosity graded (VG) paving bitumen in
- Are
we really getting quality modified paving bitumen in
6. Do we
need to add mineral filler in bituminous mixes? (Q and A)
- Applying
tack coat over prime coat: fundamentally not necessary and is gross waste
of
- Dire
need for training in asphalt technology in
1. Why roads in India
If somebody asks the “aam aadmi” (common man) in India this
question, the majority response would be: Indian highway engineers
“intentionally” construct road in such a way so that it keeps on failing
prematurely and they keep on getting “fat” budget for maintenance (pothole
repair) and resurfacing year after year.
Whereas lack of quality control is a contributing factor,
there is a major fundamental engineering problem which the Indian public does
not know. Of some ten types of bituminous paving mixes used in India ,
seven are open graded (water-trapping) mixes. Examples: Bituminous Macadam
(BM); Semi Dense Bituminous Concrete (SDBC); Dense Bituminous Macadam (DBM)
Grading 1; Premix Carpet (PMC); and Mixed Seal Surfacing (MSS). The Built-Up
Spray Grout (BUSG) is no different. The remaining three are dense graded
(desirable) mixes. Examples are: Dense Bituminous Macadam (DBM) Grading 2; Bituminous
Concrete (BC) Grading 1; and Bituminous Concrete (BC) Grading 2.
The water-trapping mixes also happen to be initially cheaper
than the dense graded mixes and therefore are used commonly. (It does not
matter if they generally last for 1-2 years compared to dense graded mixes
which may last for 7-8 years. In other words, they are very expensive based on
life cycle costs.) Water is enemy number one of bitumen. That is why,
water-trapping mixes fail prematurely especially during monsoons. All across India ,
the deadly combination of BM and SDBC is being used brazenly. PMC is also used
extensively.
Most developed countries in the world generally have three
dense graded bituminous mixes in their specifications: one each for base
course, binder course and wearing course. And they have good durable roads
despite heavy rainfall sometimes throughout the year. It is simply amazing as
to why Indian highway engineers need additional seven water-trapping,
problematic bituminous mixes for road construction/resurfacing?
Obviously, some engineers are technically ignorant about the
fundamental principle of highway engineering to keep the water away from
bituminous mixes. Others keep on using these water-trapping bituminous mixes
knowing fully well about their impending premature failure resulting in “fat”
budgets for pothole repairs/resurfacing. This is despite the fact that two
technical papers have been presented on this topic and discussed at the Indian
Roads Congress (IRC) sessions after publication in IRC journals. These two
papers give comprehensive, easy to read, technical, and economical
justifications to ban the seven water-trapping mixes such as BM, SDBC and PMC.
Interested Indian highway engineers can access and download these two IRC papers
at the following links:
Kandhal, P.S.,
V.K. Sinha and A. Veeraragavan. A Critical Review of Bituminous Mixes Used in India
Kandhal, P.S., A. Veeraragavan, and R.K.
Jain. Guidelines for Long Lasting Bituminous Pavements. Journal of the Indian
Roads Congress, Volume 71-3, 2010.
The following link to a technical note explains how the open
graded Premix Carpet (PMC) is causing havoc on city streets and rural roads.
Unfortunately, the continuation of these seven
water-trapping bituminous mixes in MORTH and IRC specifications gives them
undesirable technical legitimacy and excuse for continual use by highway
engineers across India .
Those responsible for these specifications should either (a) delete these
undesirable bituminous mixes or (b) publish an IRC paper justifying the use of
these seven mixes on technical grounds (rebutting one by one all
technical and economical arguments advanced in the aforementioned two published
IRC papers). Vague responses such as: these mixes are “good” for India; India
cannot afford “expensive” mixes (although the “cheap” mixes may generally fail
within 1-2 years and are really expensive based on life cycle costs); there are
“success stories” (if 80% projects fail prematurely and 20% survive, the latter
cannot be called “success story”); etc.; etc.
Based on past experience and recent deliberations (2012) of the
IRC Flexible Pavement Committee, there is not much hope either of these two
actions would occur in the near future. Therefore, it is up to young, rational
highway engineers of India
to challenge the old-timers who apparently have hijacked and sealed the fate of
bituminous roads in India .
[Note: Only the Jaipur Development Authority (JDA)
which maintains some 6,000 km of roads has banned all 7 water-trapping
bituminous mixes and has used only dense graded bituminous mixes since 2010.
JDA uses DBM Grading 2 for base course; BC Grading 1 for binder course; and BC
Grading 2 for wearing course in new construction as well as resurfacing. This
has resulted in smooth and durable roads, which remain largely pothole free
after bearing the brunt of the last three heavy monsoons. Example of the JDA
needs to be replicated across urban and rural India
if good roads are desirable.]
2. Potholes, potholes and more potholes in India
Unfortunately, it has become an annual ritual when during
the monsoons the Indian media reports extensively about potholes on city
streets and rural roads across India .
The coverage includes traffic jams and people dying or getting injured from
potholes. It appears highway engineers in India
are downright insensitive to do something about this yearly disgrace on their
profession.
Again, just ask “aam aadmi” (common man) about this, who
would say highway engineers are purposely not filling potholes before and
during the monsoon so that potholes grow in numbers, in size, and in depth and
they would get a “fat” budget later for pothole patching with hot asphalt mix. The
public has been brainwashed in believing potholes are a natural phenomenon
during rains (as if water in the Indian monsoon has some chemical to dissolve
the bituminous road!). Public is also told potholes cannot be fixed during the
three months of monsoon because the hot mix plants are shut down and/or
potholes are damp or wet. This is the situation after 65 years’ independence!
The above is happening despite the fact that an
“idiot-proof”, unpatented, economical, and effective readymade cold pothole
patching mix (called “Kandhal Mix” by the Jaipur Development Authority in their
contract documents) is available and which is the real answer to the
pothole problem across India . There is
no other better, generic, economical and widely field-proven product for this
purpose in India . This mix which costs
about Rs. 6 per kg can be manufactured by local contractors using local
materials. There are some patented cold mixes such as Shelmac which cost about three
times more but are still being used in India
sparingly due to high costs. Cost of patching potholes with the Kandhal mix
which can be used throughout the year is about the same as patching with hot
mix. This is because the latter is labour intensive (cutting and squaring the
pothole); material intensive (tack coat material); and equipment intensive
(roller required for compaction). Life of the Kandhal mix is equal or more than
that of the hot mix patch.
A technical paper describing the so-called Kandhal mix was
published by the Indian Roads Congress (IRC) and presented at the IRC session
in 2008. This paper can be accessed at the following link:
Kandhal, P.S.
A Simple and Effective Method of Repairing Potholes in India . Journal of the Indian
Roads Congress, Volume 69-3, October-December 2008.
It is not known at this time (November 2013) as to when the
IRC would approve this unpatented Kandhal Mix as a standard; it has been
pending there for over three years. But this is not an excuse not to use it.
The Jaipur Development Authority (JDA) is using it successfully for the last
three years with contracts worth over one crore each year. What is needed is
the WILL POWER of the highway engineers to implement this technology, proven
both in the US and India ,
in the interest of general public. All contract documents for inviting tenders
such as “G” Schedule, specifications and rate analyses are available with other
information on the performance of this mix at the following link:
3.
Why the NHAI is burying bitumen worth hundreds of crores rupees under national
highways?
The National Highway Authority of India (NHAI) has been
burying the existing bituminous roads indiscriminately under highway soil
embankments. It is especially so on many six-laning highway projects where the
road level is being raised by the NHAI to build numerous ramps for overpasses
which require soil embankments. Using existing well established asphalt
reclaiming and recycling technology, which is over 30 years old, the highly
expensive existing bituminous road can be reclaimed and recycled into a new road
to be constructed over the soil embankments (asphalt is 100% recyclable). The
bitumen and stone in the existing bituminous road are worth crores of rupees.
Bitumen is about Rs. 50,000 per ton (moreover, the country has to import more
crude from which bitumen is distilled). Net savings of about one crore rupees
can be made if one km of an existing 4-lane bituminous road is reclaimed and
recycled rather than burying it. Unfortunately, NHAI is burying kilometres and
kilometres of roads every year. No civilized country in the world buries its
bituminous road; rather reclaims the costly bitumen and stone for recycling.
Although the NHAI has been “encouraging” the contractors
through circulars for some years now, only a few NHAI contractors are
reclaiming and recycling the bitumen (called “black gold” in the industry) and
the stone; and are pocketing crores of rupees on a typical NHAI project. A vast
majority of contractors is simply and brazenly burying this country’s
“dharohar” (property) causing a great loss to the State Exchequer.
Three open letters have been sent
to the Chairman of NHAI since November 2011 to make the reclaiming/recycling of
the existing bituminous road mandatory to put a stop to this great loss
to the State Exchequer, which is estimated to be hundreds of crores every year.
However, the NHAI has not taken any action (they are still in the “encouraging”
mode). Therefore, this national loss is continuing due to NHAI’s incompetence,
indecisiveness and lack of accountability.
Copy of the third open letter to
the NHAI Chairman can be accessed at the following link:
Asphalt milling and recycling is a
well established technology as mentioned earlier and has been used for over 30
years across the world. Asphalt pavement guidelines prepared by Prof. Prithvi
Kandhal and Dr. Rajib Mallick for the US Federal Highway Administration (FHWA)
can be accessed at the following link:
4.
Are we really getting viscosity graded (VG) paving bitumen in India ?
It is very unfortunate that many Indian highway engineers
still do not know that it is illegal and unethical to specify, produce, and use
penetration graded paving bitumens such as 60/70 and 80/100.
The Bureau of Indian Standards (BIS) revised IS:73
Specification for Paving bitumen in July 2006. The revised specification
IS:73:2006 outlawed the old (more than 100 year old) penetration grades such as
60/70 and 80/100 and adopted new viscosity grades (VG) such as VG-30 in lieu of
60/70 and VG-10 in lieu of 80/100. [Prof. Prithvi Singh Kandhal was
instrumental in introducing the viscosity grading of paving bitumen in India in
2005 with the assistance of 10 Jan Path, New Delhi.]
The Ministry of Road Transport and Highways (MORTH) issued
Circular No. RW/NH-33041/3/2001-S&R (R)-Vol. III on 04/08/2008
to all the state PWDs, NHAI etc. reminding them to implement the new bitumen
viscosity grades as soon as possible. According to the circular, the user must
substitute VG-30 in lieu of 60/70, substitute VG-10 in lieu of 80/100, and
substitute VG-40 in lieu of 30/40 or 40/50 grades. Is that really hard to do?
Just changing the nomenclature in tender notices or project reports is not a
rocket science!
If the user would like to know more about viscosity grades
(VG), please read the following IRC paper; it can also be downloaded at the
link provided.
Kandhal, P.S. An Overview of the Viscosity Grading System
Adopted in India for
Paving Bitumen. Indian Roads Congress, Indian Highways, April 2007
The BIS has further revised IS:73:2006 Specification for
Paving Bitumen in April 2013. The revised IS:73-2013 has the following
significant changes. Instead of specifying a penetration range for each VG
grade, only minimum penetration values have now been specified. For example:
minimum penetration of 80 for VG-10 and 45 for VG-30. Instead of specifying the
minimum absolute viscosity at 60 C, viscosity range has been specified for each
VG grade. For example: 800-1200 poises for VG-10 and 2400-3600 poises for
VG-30. These revisions were warranted and justified as explained in the IRC
paper above.
Progressive user agency (be it PWD, contractor, consultant,
testing laboratory or university) must purchase the viscosity testing equipment
as soon as possible to monitor the grade and quality of the VG bitumen supplied
by the oil companies. Research study completed by IIT Madras for BIS in 2011 determined
that a significant percentage of VG-30 bitumen samples obtained across India
were actually either VG-20 or VG-10; that is, softer viscosity grades which may
cause premature rutting/bleeding in the asphalt pavements. Therefore, the user
agencies must test at least the absolute viscosity at 60 C to ensure right VG
grade is being supplied to the project. Only the vacuum capillary viscometer
(and not the Brookfield viscometer)
can be used for determining the absolute viscosity at 60 C. Brookfield
viscometer can be used to determine the kinematic viscosity at 135 C in
addition to kinematic capillary viscometer.
Click at the following link to access Prof. Kandhal’s
technical note on equipment details and testing procedure:
5. Are we really getting quality modified paving
bitumen in India ?
In recent years, traffic loads and tyre pressures have
increased, which has created a situation for which modified bituminous binders
are needed. In the past, the following two specifications have been used by the
highway agencies for specifying modified binders.
- Indian Roads Congress Publication SP:53-1999, “Tentative Guidelines on Use of Polymer and Rubber Modified Bitumen in Road Construction”, December 1999.
- Bureau of Indian Standards. IS 15462:2004, “Polymer and Rubber Modified Bitumen – Specification, 2004.
Four types of modified binders are included in the preceding
two publications: Polymer Modified Bitumen or PMB (elastomer), PMB (plastomer),
Crumb Rubber Modified Bitumen (CRMB), and Natural Rubber Modified Bitumen
(NRMB). Since these are different types of modified bitumen materials, separate
specifications and criteria in form of four tables are included as is the
practice across the world.
These four modified binders are described briefly below.
Elastomers: Elastomeric polymers have the ability to
resist permanent deformation and cohesive failure in the bituminous mix by
stretching and then recovering their shape when the deforming force is removed
similar to a rubber band. Therefore, PMB (elastomer) is resistant to rutting as
well as fatigue cracking.
Plastomers: Plastomeric polymers form a tough, rigid,
three dimensional networks within the bitumen. These plastomers give high
initial strength to the bitumen to resist heavy loads. However, plastomers may
crack at high strains. Therefore, PMB (plastomer) is primarily resistant to
rutting.
CRMB: Rubber from discarded tyres is ground to a
particulate or crumb prior to adding it to bitumen to produce CRMB. CRMB is
much more complex and least understood compared to PMBs with elastomers.
Because of the complex and varying chemical composition of crumb rubber
obtained from tread/side wall of truck and/or car tyres, its compatibility with
bitumen is always questionable. That is why; CRMB has given mixed performance
in the US .
The quality control requirements right from the production
to the end use of CRMB are too cumbersome because of two issues: (a) crumb
rubber tends to separate and settle down in the bitumen and (b) crumb rubber is
prone to degradation (devulcanization and depolymerization) if it is maintained
at high temperatures for more than 6-8 hours. These quality control
requirements for CRMB, which are hardly followed in India ,
are given in the following IRC paper which can be downloaded at the link
provided.
Kandhal, P.S., “Quality Control Requirements for Using
Crumb Rubber Modified Bitumen (CRMB) in Bituminous mixtures”, Journal of the
Indian Roads Congress, Volume 67-1, 2006.
NRMB: Natural rubber modified bitumen is manufactured
by adding natural rubber (which is available in south India )
to bitumen. However, NRMB should be used with caution because like CRMB it has
degradation problems if kept at high temperature for too long.
However, the Flexible Pavement Committee (FPC) of the Indian
Roads Congress (IRC) pulled a surprise in 2010 by revising IRC:SP:53-1999. The
revised IRC:SP:53-2010 contains a “unified” single specification table for all
four types of modified binders, which is not technically possible unless the
unified specification is performance based which it is not. It was like mixing
apples with oranges. The elastic recovery requirement was arbitrarily lowered
to accommodate the CRMB. This IRC:SP:53-2010 has the following problems:
(a) Lowering the requirements to
the level where a weak modifier like crumb rubber can also qualify, would lower
the performance standard for all modifiers;
(b) Suppliers of better and more
expensive products will tend to downgrade the quality of their products so as
to be more competitive price wise if that is the criterion for decision making; and
(c) Lowering the quality will
come in the way of producing still better products thus having a negative effect
on further R&D activities.
Therefore, the highway agencies (government and contractors)
who believe in quality should NOT specify the revised IRC:SP:53-2010. They
should only specify: Bureau of Indian Standards. IS 15462:2004, “Polymer and
Rubber Modified Bitumen – Specification, 2004 which remains unchanged in terms of
four separate tables. PMB (elastomer) only should be demanded in the
specifications in clear terms.
Detailed information on all types of modified binders
including their characteristics, specifications and recommended uses in highway
construction are given in the following IRC paper which can also be downloaded
at the given link.
Kandhal, P.S. and M.P. Dhir. Use of Modified Bituminous
Binders in India :
Current Imperatives. Journal of the Indian Roads Congress, Volume 72-3,
October-December 2011.
The following salient recommendations have been made in the
preceding IRC paper:
1. Polymer modified bitumen (PMB) with elastomers is most
commonly used with success on major highways in the developed countries because
elasticity in this PMB provides resistance to both rutting and fatigue
cracking. Such PMBs are also relatively more stable and maintain their
integrity better compared to PMBs with plastomers, CRMB, and NRMB (natural
rubber modified bitumen). Superpave performance grades have been made
successfully with these PMBs. PMBs with elastomers are therefore recommended
for heavily trafficked roads in India .
2. Polymer modified bitumen with plastomers are hardly used
in flexible pavements in the developed countries because although they provide
higher strength initially, they are prone to cracking at high strains and do
not rebound after deforming force is removed. Therefore, there is no need to
have a specification in India for PMBs
with plastomers to avoid its unnecessary and improper use, until proper
technical justification is provided.
3. Natural rubber modified bitumen (NRMB) has limited use to
support the local industry in southern India .
It should not be used on heavily trafficked roads where only PMBs with
elastomers should be used as mentioned earlier. However, NRMB should be used
with caution because like CRMB it has degradation problems if kept at high
temperature for too long.
4. CRMB is much more complex and least understood compared
to PMBs with elastomers. Because of the complex and varying chemical
composition of crumb rubber, its compatibility with bitumen is always
questionable and therefore it has given mixed field performance. Besides, it
has potential settling and degradation problems as mentioned earlier.
Therefore, CRMB is not recommended for use in India
on heavily trafficked roads. It can be considered for use on medium trafficked
roads its elastic recovery is considerably lower than that of PMBs with
elastomers. However, it should be blended on site in close proximity of hot mix
plants so that it can be used within 6-8 hours after production. Claims that
the so-called “chemically modified” CRMB in India
does not have settlement and/or degradation problems have not been validated as
yet with any reported meaningful field test data. Obviously, if on-site
blending is done, a fully equipped testing laboratory staffed with qualified
technicians should be mandatory at the blending terminal.
5. Use of any modified binder in bituminous mix on low
volume rural roads such as PMGSY is detrimental to their durability. The
current practice of using CRMB in such applications should be discontinued
until proper technical justification is provided.
6. Do we need to add
mineral filler in bituminous mixes? (Q and A)
It is not understood as to why some engineers in India
are obsessed with adding some sort of mineral filler (such as portland cement)
when the baghouse fines (stone dust) are abundantly available and are as good
as those fillers. It is simply a waste of money. The US
has one of the best roads in the world, if stone dust works there, why not in India ?
Hydrated lime can be added if moisture susceptibility is a problem based on mix
design test such as AASHTO T 283 as specified in the IRC standards.
There are many other issues related to mineral fillers
including stone dust. Mr. Rajib Chattaraj, Executive Engineer P.W.D. West
Bengal had asked Prof. Prithvi Singh Kandhal some
interesting and good questions about the use of mineral fillers in bituminous
mixes in India . Those Questions and
Answers (Q and A) should be of interest to the highway community in India
and can be accessed and downloaded at the following link:
Prof. Kandhal had the privilege of leading research on
mineral aggregates and fillers (including baghouse fines) at the national level
in the US . The latest Information
Manual on Baghouse Fines currently in use in the US
was authored by him. Therefore, the responses to Mr. Chattaraj’s questions are
based on his opinions considering the latest research on this subject.
7. Applying tack coat over prime coat: fundamentally not
necessary and is gross waste of India ’s resources !
Are you applying tack coat over prime coat? If so, it is
fundamentally not necessary and it is a sheer waste of India ’s
resources. Unfortunately, MORTH orange book (2013) Section 503 Tack Coat and
Indian Roads Congress IRC: 16-2008 Code for Prime Coat and Tack Coat require
tack coat over prime coat.
About 57 crores of rupees are wasted each year by
unnecessarily applying tack coat over prime coat. If this useless practice is stopped, India
would also need to import less petroleum crude oil because bitumen in the
emulsion is obtained from crude oil.
Detailed technical justifications for eliminating the need
for tack coat over prime coat and the associated extent of wastage of
taxpayers’ money and India ’s resources
can be accessed and downloaded at the following link:
MORTH should immediately issue a corrigendum to the
2013 Orange Book “Specifications for Road and Bridge Works” eliminating the
requirement of tack coat over prime coat. Time is of essence. In the
meantime, project engineers must use common sense, show their guts, and
eliminate this requirement from the project to realize savings in the interest
of country.
8. Dire need for training in asphalt technology in India , where is the vision?
Just ask a typical highway engineer in India
the following two questions:
(a) Which
paving grades of bitumen are used in India ?
[Most engineers would say 60/70 and 80/100 although these penetration grades
have been outlawed and replaced with Viscosity Grades (VG): VG-30 and VG-10
since 2006.]
(b) How
would you determine if part of the paving bitumen has been replaced with marble
dust during transport from refinery to the project site? [Most engineers would
not be able to answer. They do not know about the very simple bitumen
solubility test to determine the presence and amount of insoluble like dust in
the bitumen.]
The preceding two questions are
about the paving bitumen only, which is the most important and most expensive
ingredient in bituminous mixes (about Rs. 50,000 per ton). There are other
areas such as aggregate; mix design; construction; maintenance; and recycling.
Most highway engineers in India are
technically ignorant in those areas as well. The so-called “smart” engineer’s
knowledge is generally limited to the specification book only.
Unfortunately, no quality road
construction can be expected if the highway engineers are technically ignorant.
It is just common sense.
Now, who is responsible for this
technical ignorance prevailing among most highway engineers in India ?
The engineering institutions cannot be blamed because there is hardly a course
(if any) on highway engineering in the civil engineering curriculum. It is the
responsibility of the employers (such as MORTH, NHAI, State PWD, and
contractors) who hire the civil engineers for highway design and construction
activities to train them. Good example: Indian Railway gives extensive training
to civil engineers selected for railway engineering services.
Even a small percentage of Rs.
75,000 crores, say 0.1 percent or 75 crores spent per year on this training
will go a long way to achieve quality road construction across India ,
which is the need of the day. That is hardly any price for quality. Helen
Keller has said, “The only thing worse than being blind is having sight but no
vision.” The question is: Does the MORTH and NHAI have the vision?
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