A Simple Guide For Producing and Placing Readymade Pothole Patching Mix in Accordance With IRC:116-2014
A Simple Guide For Producing and Placing Readymade Pothole Patching Mix in Accordance With IRC:116-2014
A Simple Guide For Producing and Placing Readymade Pothole Patching Mix in Accordance With IRC:116-2014
By
Prof. Prithvi Singh Kandhal
Associate Director Emeritus
National Center for Asphalt Technology
Auburn University, Alabama USA
pkandhal@gmail.com
Home page: www.eng.auburn.edu/users/kandhps
8 September 2018
“American roads are good not because America is rich, but America
is rich because American roads are good.” - John F. Kennedy
1
The following two guidelines are presented in this document:
A. Guidelines for Producing Readymade Pothole Patching Mix in accordance with Indian
Roads Congress Specification IRC:116-2014
B. Guidelines for Placing Readymade Pothole Patching Mix in accordance with Indian
Roads Congress Specification IRC:116-2014
1. BACKGROUND
These guidelines pertain to the Indian Roads Congress Specification IRC:116-2014,
“Specifications for Readymade Bituminous Pothole Patching Mix Using Cutback Bitumen”.
This readymade pothole patching mix does not require any preparation of the pothole such as
squaring and applying tack coat; the mix is simply taken out of the 50-kg bag, leveled with a
rake, hit with a hand rammer by ordinary laborer (no roller), some light sand or grass/leaves is
sprinkled on surface to prevent pick up by vehicle tyres, and opened to traffic right away. If there
is water in the pothole, simply sweep off the extra water. The patch will outlast the adjacent road
area. The mix has a storage life of at least 6 months, so it can be prepared in advance and used as
needed to repair potholes as soon as they develop throughout the year.
Cost analyses have shown the cost of this unpatented, generic pothole patching mix is about one-
third the cost of many commercial, patented readymade mixes available in India. Cost analyses
have also shown the cost of repairing potholes with readymade cold mix is less than the cost of
repairing with hot mix asphalt because the latter is more labour intensive (squaring the pothole),
material intensive (binder for tack coat), and equipment intensive (need for roller). Moreover, hot
mix cannot be used during rainy season and extreme cold winter. Therefore, this mix can be
used throughout the year including hot summer.
This mix is also very handy for contractors who are responsible for maintaining national
highways, state highways or rural roads during the concession or warranty or defect liability
period. If there are a few potholes there is no need to arrange hot mix; take some bags of this
readymade cold mix and a labourer (with a hand rammer) in a car or pickup and get the potholes
repaired. It is also handy for filling test/survey pits made on the road for testing and also for
filling utility cuts in city streets.
This readymade cold pothole patching mix was developed by Prof. Prithvi Singh Kandhal while
serving as Chief Asphalt Road Engineer of the US State of Pennsylvania Department of
Transportation. Pennsylvania has the fourth largest highway network in the US. His R&D work
on this mix was published by the US Transportation Research Board in Transportation Research
Record No. 821, 1981. This mix has been used in the US with success during harsh cold and
rainy weather when hot mix cannot be used.
2
Under the US Strategic Highway Research Program (SHRP), it was decided to conduct a field
performance study of some 10 different pothole patching mixes/applications in 4 different
extreme climatic regions of the US. The mix developed by Prof. Kandhal was adjudged as the
best performing patching mix in that study because 78% patches made with this mix survived
after 4 years’ service in the field. Most other patches had failed miserably to different degrees by
that time and so the field study was terminated.
Based on the successful field application of this readymade mix by the Rajasthan PWD and the
Jaipur Development Authority, the Indian Roads Congress adopted it as Specification IRC:116
in 2014. Since it is unpatented, the mix can be produced by any highway agency/contractor using
locally available materials. These simple guidelines explain how it can be done easily.
To facilitate inviting tenders for supply and placement of this readymade pothole patching mix,
the following three items should be inserted in the BSR of highway agencies such as PWD;
CPWD; BRO; MES; and cities/municipalities.
1. Supply of readymade cold bituminous pothole patching mix in accordance with IRC:116-
2014 Specifications in 50-kg plastic-lined sturdy bags with 10-km average lead. Mix
shall contain at least 5.6% MC-800 Cut-back Bitumen and suitable anti-stripping agent.
Mix shall be workable and usable for at least 6 months. All 50-kg bags shall be
transported to a storage facility designated by the Engineer. Since the mix contains
volatile kerosene, sealed bags shall not be stored in a closed building or warehouse. No
open flame or smoking shall be permitted near the stored mix.
Cost Rs. 370 per 50-kg bag
2. Placing and compacting readymade cold bituminous pothole patching mix in potholes in
accordance with IRC:116-2014 Specifications from 50-kg plastic-lined sturdy bags with
20-km average lead. Cost Rs. 23 per 50-kg
3. Supply, placing and compacting readymade cold bituminous pothole patching mix in
accordance with IRC:116-2014 Specifications in 50-kg plastic-lined sturdy bags with 10-
km average lead for supply and 20-km average lead for placement. Mix shall contain at
least 5.6% MC-800 Cut-back Bitumen and suitable anti-stripping agent. Mix shall be
workable and usable for at least 6 months. All 50-kg bags shall be transported to a
storage facility designated by the Engineer. Since the mix contains volatile kerosene,
sealed bags shall not be stored in a closed building or warehouse. No open flame or
smoking shall be permitted near the stored mix. Cost Rs. 393 per 50-kg
bag
Most highway agencies require rate analyses to support the items in the BSR. The rate analyses
performed recently for these items are given in Annexures A and B. Therefore, the government
agencies now have all the material to issue NITs (notice inviting tender).
3
3. MIX PRODUCTION GUIDELINES
Mix production consists of procurement of necessary materials; mixing operations; and packing
which are described below:
Please note that the dust content (% passing 0.075 mm sieve) of the aggregate should not exceed
2 percent otherwise the mix will not be tacky and will not bond in the pothole and will also lose
its workability. Note that we are not applying tack coat on the pothole. The aggregate should be
angular and should meet all the quality requirements which are specified for dense graded hot
mix asphalt such as Bituminous Concrete (BC). Refer to IRC:116-2014 for details.
The aggregate should be dry before it is mixed with MC-800 Cutback Bitumen. If it is not
already dry, it should be processed through the dryer of a portable mixing plant or a drum plant.
This type of processing also helps in reducing the dust content of the aggregate if it is excessive.
CAUTION: Under no circumstances, MC-800 should be added during the aggregate
drying operation. This is because MC-800 has volatile kerosene in it, which may cause
explosion and serious accident when it is used near open flames.
Before the dry aggregate is mixed with MC-800, its temperature can range from 25 to 65℃. This
means dry aggregate need not be heated. Warming the aggregate just facilitates good mixing.
4
Temperature should not exceed 65 ℃ otherwise very hot aggregate would evaporate the volatile
kerosene in MC-800 and make the mix stiff and unworkable.
MC-800 Cutback Bitumen: MC-800 Cutback Bitumen should meet BIS Specification IS:217
Specification for Cutback Bitumen. It is available in 200-liter drums on request from most
approved bitumen suppliers in India. [For information only, HINCOL and Tiki Tar are supplying
to contractors in Rajasthan. Jalnidhi Bitumen Specialties also manufactures MC-800. There are
more.] Contact your local bitumen supplier. Ask your supplier to furnish a test report showing
MC-800 meets IS:217.
Under no circumstances, MC-800 should be manufactured by government agencies or
contractors because not only it is unsafe, it also requires several tests to be conducted (especially
kinematic viscosity at 60 C) to meet IS:217 Specifications.
Anti-Stripping Agent: The readymade patching mix may be placed in wet potholes and it has to
survive during rain/freezing temperatures. Therefore, a suitable anti-stripping agent MUST be
added to MC-800 bitumen prior to its mixing with dry aggregate. There are many suppliers of
liquid anti-stripping agents which are also used in hot asphalt. [Some of the suppliers in India are
HINCOL; Petrochem; Akzonobel; Zydex Corp.; and Opal Paint. There are other others, ask your
bitumen supplier.]
Tell your supplier what type of mineral aggregate (such as quartzite; sandstone; limestone; and
granite) you are using. This is because there are numerous types of anti-stripping agents (with
their own dosage rates) which are compatible with specific aggregate types.
Try to get 2-3 types of anti-stripping agents. Conduct the following three very simple tests to
determine which anti-stripping agent is most suitable for your aggregate and how much dosage
(percent by weight of MC-800) is needed.
5
percent of retained coating while the sample remains immersed in water, which should be at least
95 percent.
C. Water Resistance Test (Boiling water test)
Fifty grams of patching mix, whether freshly prepared or taken from the stockpile or a sealed
bag, shall be heated at 120 ℃ in a laboratory oven for 1 hour, cooled to 95 ℃ in laboratory air,
and then placed in 400 ml of boiling water in a 600-ml glass beaker and stirred with a glass rod
at the rate of 1 revolution per second for 3 minutes. The water shall be decanted and the mix
shall be spread on an absorbent paper for visual observation of the coating. The aggregate shall
be at least 90 % coated with a bituminous film.
50-kg Plastic-Lined Sturdy Bags: Procure the desired number of 50-kg plastic-lined, sturdy,
woven bags (sacs). These are readily available in the market and are used for storing agricultural
seeds. Plastic lining is necessary so that the kerosene in MC-800 does not evaporate and mix
maintains its workability for at least 6 months as specified. Choose a sturdy variety for the bag
cloth because angular stones in the mix may pierce the bag. Typically, these bags cost Rs. 15
each. You can get your own bags stitched up locally like Riya Construction in Jaipur does. Label
the bag: Readymade Pothole Patching Mix – Meets IRC:116 Specification.
Now that we have procured all the necessary materials: aggregate; MC-800; suitable anti-
stripping agent; and packing bags, we are ready to make the mix as explained next.
6
Table 2. Minimum total MC-800 content by weight of mix
Aggregate water absorption, Minimum Total MC-800 by weight
% of mix, %
Less than 1.0 5.6
1.1 to 1.5 6.2
1.6 to 2.0 6.9
(a) Small Portable Drum Mixing Plant: If readymade patching mix is to be prepared in
small, limited quantities, the small portable drum mixing plant as shown in Photograph 1
has been used in Rajasthan. This type of plant has been used to provide hot mix such as
premix carpet. It consists of a small rotating drum with flame on one end; aggregate is
introduced at this end. Paving bitumen such as VG-30 is introduced at the other end. So,
like a typical large hot mix drum plant, aggregate is dried, heated, and mixed with
bitumen in the drum. The mixed material is discharged at the other end.
CAUTION: Now, to produce readymade patching mix, we have to be very careful that
we do not introduce MC-800 containing volatile kerosene into the drum with a flame
burning. As mentioned earlier, this would pose safety hazard. Therefore, we can either
dry and heat the aggregate or mix with MC-800. We cannot do both operations at the
same time.
If the aggregate is not already dry, it should be heated in the drum with flame and
discharged on the other end without adding MC-800. Then, the dry aggregate can be re-
introduced in the drum without flame and MC-800 added. The mixed material is
7
collected at the other end with a wheel barrow and stacked for placing in the bags later.
The mix should have near 100% coating of bitumen.
The mix should be such that it can be stocked, handled, placed, and finished without
stripping of the bitumen from the aggregate. To help prevent stripping and avoid heat
buildup in a stockpile (which may burn the entire stockpile due to chimney effect), the
mixed material should not be stockpiled no higher than 1.5 m for the first 48 hours. The
stockpile then can be raised in height and made conical in shape.
Conduct the following boiling test (Water Resistance Test) on the mixed material, as also
mentioned earlier.
Fifty grams of patching mix, whether freshly prepared or taken from the stockpile or a
sealed bag, shall be heated at 120 ℃ in a laboratory oven for 1 hour, cooled to 95 ℃ in
laboratory air, and then placed in 400 ml of boiling water in a 600-ml glass beaker and
stirred with a glass rod at the rate of 1 revolution per second for 3 minutes. The water
shall be decanted and the mix shall be spread on an absorbent paper for visual
observation of the coating. The aggregate shall be at least 90 % coated with a bituminous
film.
8
3.3 Quality Control and Acceptance of Mixture
The composition of the produced mix (gradation and bitumen content) should be tested by an
independent, approved testing laboratory before acceptance by the Engineer. Before conducting
the bitumen extraction test to determine residual bitumen content in the patching mix, the sample
should be cured completely to remove all kerosene. Curing should be done as follows. Place the
loose mix in an open metal container and heat slowly on a hot plate with frequent stirring until a
constant weight is achieved.
The following two tests should be performed by the contractor (in presence of a Department
representative) on the mixture, freshly prepared or taken from a stockpile or sealed bag at any
time during its storage life (usually 6 months).
(i) Water Resistance Test (Boiling Test) as described earlier
(ii) Workability Test
The water resistance test would indicate whether the patching mix has a potential for stripping in
the pothole in presence of water. If the mix fails this test, it means a proper type and/or amount
of an anti-stripping agent has not been used in the bituminous binder.
The workability test should be conducted as described below:
Approximately 2.5 kg of the patching mix shall be cooled to –7ºC in a freezer. After cooling, the
mixture shall be capable of being broken up readily with a spatula that has a blade length of
approximately 200 mm. This test shall be performed when the mix is produced and thereafter
anytime during storage. If the mix is not workable at –7ºC, it shall be rejected and the
composition of the mix shall be properly modified (for example, by increasing the bitumen
content and/or gradation changes). This test is also applicable in areas with hot climate because it
amplifies the workability characteristics of the mix by using a lower test temperature.
If the mix fails in workability it could be due to improper bitumen type, low bitumen content,
excessive fines or improper gradation. Even one-half percent lower bitumen content can make
the patching mix unworkable and useless.
Stocked patching material may be rejected, at any time during the six-month period if, in the
opinion of the Engineer, the patching material has stripped (more than 10% uncoated particles)
or otherwise become unfit or unworkable for use.
9
Use a large scale to ensure each bag is filled with 50 kg of readymade mix. Sew (seal) the top of
the plastic-lined sturdy bag to ensure that the kerosene in MC-800 does not escape from the mix
and the mix remains workable for at least 6 months.
The packed bags should be stored in an open building/godown with good ventilation so that the
kerosene vapor (in case of leakage) does not accumulate inside and create a potentially
hazardous situation.
5. REFERENCES
3. 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.
4. Kandhal, P.S. Bituminous Road Construction in India. Textbook cum Reference Book.
Prentice Hall of India, New Delhi, July 2016.
SCOPE
These guidelines apply to readymade, cold patching mix prepared in accordance with Indian
Roads Congress Specifications IRC:116-2014, “Specifications for Readymade Bituminous
Pothole Patching Mix Using Cut-Back Bitumen”.
MATERIALS
1. Readymade patching material packed in plastic-lined, 50-kg bags with a storage life of at
least 6 months. [For estimation purposes, one 50-kg bag is sufficient to fill pothole(s)
measuring 2/3 cu ft in volume.]
2. Sand to be sprinkled on compacted patch so that traffic tyres do not pick the patching
mix. [Some agencies spread plant leaves on the patch to achieve the same purpose.]
10
TOOLS
1. Wire brush to loosen disintegrated asphalt/debris in the pothole
2. Ordinary road brush to remove debris and dust from the pothole
3. Suitable large scoop to remove mix from the bag and place in the pothole
4. Rake with long handle to level off the loose mix before compaction
5. Hand-held rammer with a heavy, steel base to compact the mix in pothole
6. Shallow tray with water to moisten the base of the rammer so that bitumen-rich mix
does not stick to it during compaction
PROCEDURE
1. If the pothole is filled with rainwater, sweep off the excess water from the pothole.
Pothole need not be dry.
2. Use wire brush to loosen existing disintegrated asphalt mix/debris in the pothole.
3. Use ordinary road brush to remove loose debris/dust from the pothole to make it clean.
4. Open the 50-kg bag and place sufficient cold mix in the pothole using a large scoop so
that after compaction the patch is about 10-12 mm above the adjoining road surface.
Traffic will then densify the patch later and make it almost level to road surface. Level
the loose mix with a rake before compaction.
5. If the pothole is about 75 mm or less in depth, all mix can be placed in one lift (layer) and
compacted. If the pothole is deeper than 75 mm, then the mix should be placed in layers.
Each layer should not exceed about 75 mm and should be compacted adequately with
hand-held rammer before placing the next layer.
6. After the patching mix is placed in the pothole, compaction should be accomplished with
a hand-held rammer (Photograph 2). First, the periphery of the patch should be
compacted adequately and then compaction should proceed inwards toward the center of
the patch. Moisten the bottom of the hand-held rammer frequently with water in shallow
tray so that the bitumen-rich patching mix does not stick to the rammer. Compaction
should be carried out until there is little movement of the mix when pressed with shoes.
The compacted patch should be about 10-12 mm higher than the adjoining road surface
as mentioned earlier. Note: If there are too many potholes on a road, it is advisable to use
either a vibratory compaction plate or a small roller to expedite the patching operation. In
that case, the compacted patch should be about 5-6 mm higher than the adjoining road
surface.
7. Sprinkle some sand on the compacted patch so that traffic tyres do not pick the bitumen-
rich mix. [Some agencies spread plant leaves on the patch to achieve the same purpose.]
8. The patch can now be opened to heavy traffic such as car and truck, which is actually
helpful in further compacting and locking the patch in place. Bikes may leave mark on
the patch but it would be ironed out by heavy traffic.
9. If the pothole is very deep and it is desired to economize on the use of readymade
patching mix, it can be done as follows. Clean the pothole and spray a thick film of MC-
30 cutback bitumen at the bottom as a tack coat. Place graded aggregate of 50 mm
11
maximum size in the pothole and compact it well in layers. Spray another tack coat of
MC-30 on compacted aggregate. Place and compact at least 75 mm of the readymade
pothole patching mix at the top.
ANNEXURE A
Cost Analysis of Supplying Readymade Bituminous Pothole Patching Mix (IRC: 116-2014)
to Department Godown
(Revised 6 April 2017)
Assume one ton (1000 kg) of the mix is to be made and filled in 20 bags of 50 kg each, which
will be supplied to Department Godown for use later.
A. Cost of Materials
12
B. Production Cost
Total 6724.58
Add 10% contractor’s margin……………………………………… 672.46
13
ANNEXURE B
Total 2,904.00
Add 4.5% for royalty, sales tax, income tax, etc……………….. 130.68
Total 3325.08
Total 3657.59
****************************************************
14