microsurfacing paper issa world congress_english
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MicrosurfacingTRANSCRIPT
7th ISSA WorldCongress, Lyon 2010
Micro surfacing as Pavement Preservation Technology
TK Subhash Product Manager, Shell India Markets Pvt Ltd
Abhishek Biswas Business Development Manager, Shell India Markets Pvt
Ltd
Janyajarasporn Yutthaporn Regional Technical Manager AP/IN/ME The Shell Company of
Thailand Ltd
Frits DeJonge Global Technology Excellence Manager, The Shell
Company of Thailand Ltd
ABSTRACT
With hosting the Commonwealth Games 2010, the city of Delhi is gearing up its preparations for this
mega event. Plans are underway for the provision of supporting facilities that cater for the
requirements, which will arise during the influx of tourists and sports enthusiasts. The city is
undergoing a major facelift in order to provide adequate infrastructure by 2010 and the Government
of India is spending circa $17.5 billion for overall modernisation of the capital city.
Transport is one of the significant areas under consideration by the planners. In particular, the roads
providing the connectivity to the games stadium, hospitals and the games village are under focus.
The total area to be paved is around 650,000 square meters.
The city roads were overlaid three years ago with 50mm (2 inches) of asphalt concrete. After three
years, the surface was rough and in some places heavy rutting defaults were observed. The
pavement did not show any sign of structural weakness. The New Delhi Municipal Corporation
(NDMC) was looking for the most cost effective alternatives to restore the surface conditions to the
required level with regards to surface integrity and skid resistance.
The NDMC was facing several important constraints:
· Heavy traffic during the day time making construction works during these hours impracticable
· A short duration for carrying out the works
· A ban of Hot Mix Asphalt Plants within the city limits
· Drainage constraints if the final pavement thickness increased significantly
These constraints encouraged the NDMC to look at other solutions and micro surfacing was
considered as an alternative
Key words: micro surfacing, pavement, cost effective solution
1. Introduction
The Delhi metropolitan area lies within the National Capital Territory of Delhi (NCT). The 2010
Commonwealth Games has provided a boost for the infrastructure in Delhi. The Government has
planned to re-lay roads and install new electric lighting before the 2010 Games. By October 2010, all
major roads in Delhi will have been revamped, freshly resurfaced and with new road markings. The
public works department (PWD), the major road owning agency, has drawn up a map for micro
surfacing of all stretches which were laid or resurfaced three years ago. The department has
reportedly finalized the plan to use micro-surfacing technology to resurface over 400 kms length of
PWD roads in the national capital.
Maintenance is an essential activity for providing the required serviceability and durability of a
pavement to the road user. It is established that appropriate and timely maintenance extends the
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service life of a pavement considerably. In construction and maintenance of roads by conventional
hot mix technologies, energy inputs begin from quarrying of stones and continue until the asphalt
mixture is finally installed. Cold mixed technologies involving use of bitumen emulsions provide
effective, energy efficient and long lasting solutions. The use of surfacing such as micro-surfacing
are ideally suited to the maintenance of urban roads, as applications are thin enough so that utility
accesses and curbs do not need adjusting. Maintenance of roads and roundabouts in New Delhi has
become increasingly difficult and the subject of much debate with the closure of hot mix plants by
Honorable Supreme Court of India.
Micro surfacing is considered as an alternative to thin hot mix renewals. The project attracted wide
media attention. The advantages of micro surfacing were widely reported in many major daily
newspapers. The articles described the performance of pavements treated with micro-surfacing
technique for a wide climatic temperature range.
This paper discusses the specification adopted, experiences gained and the performance of micro
surfacing on busy urban roads in New Delhi.
2. Pavement Condition
Table 1 below provide guidelines on serviceability indicators
Table 1: Guidelines for Maintenance of Pavements (Indian Road Congress, 1997)
Guidelines for Maintenance
Serviceability
Indicators
Urban (Heavy Traffic) Urban (Light Traffic)
Preventive Periodic Preventive Periodic
Benkelman
Beam
Deflection, mm
(maximum)
0.8 0.8 1.2 1.2
Distress, %
(maximum)
5 10 5 10
Roughness,
mm/km
(maximum)
2500 3500 2500 4000
Rutting, mm
(maximum)
8 16 8 16
Vehicle
Damage Factor
(maximum)
4 4 2 2
Thickness, mm 4-6 7-8 3-4 6-8
Quantity of
aggregate,
kg/m2
10-12 14-16 6-7 12-14
Type of grading III III II II
The pavements chosen for micro-surfacing treatments are often found to have severe rutting in
some locations and minor cracks can also be present, however the overall pavement condition is
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relatively good.
3. Constraints
The major constraints encountered on Delhi road maintenance are as follows:
- Heavy traffic during day time making work during day time impossible
- Duration of traffic block
- Ban of Hot Mix Asphalt Plants within city limits, therefore hot mix is required to be transported over
long distances
- The pavement thickness increase due to hot mix and subsequent issues of drainage / utilities
Considering the above constraints, micro-surfacing technology was adopted by NDMC
4. Application:
Key success elements identified for this project are:
- Opening to traffic in 1 hour and minimal interruption to traffic
- Chemistry and selection of emulsion components
- Emulsion properties for good and durable road performance
- Understanding aggregate quality, weather conditions and fine tuning the emulsion chemistry
- Application machinery and operators competence
- Construction procedures and management
The processes involved identification of aggregate sources, choosing the right gradation, designing
the emulsion as per aggregate and climatic conditions and skilful execution of the project. Each
stage of the process will be discussed briefly in turn
4.1 Identification of aggregate
The aggregates were identified after an extensive search in the region. The finalised source is from
Bahadurgarh, which is 120 km away from the project site.
The aggregate type is evaluated to be granite. The properties of aggregates as per Recommended
Performance Guidelines for Emulsified Asphalt Slurry Seal, 2005 - A 105 are evaluated in Table 2
(International Slurry Surfacing Association, 2005)
Table 2: Aggregate properties
Quality Test Method Specification Values
Sand
Equivalent
ASTM D 2419 -
2009
> 45 70
Abrasion
Resistance (%)
ASTM C 131 -
2006
< 35 12
4.2 Choosing the Aggregate Gradation
When tested in accordance to AASHTO T27 - 2006 (ASTM C136 - 2006) and AASHTO T11- 2005
(ASTMC117 - 2004), the target (mix design) aggregate gradation (including the mineral filter) shall
be within the band given in Table 3 below (International Slurry Surfacing Association, 2005)
Table 3: Aggregate Gradation as per ISSA Type III
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ASTM No #mm Type III
Lower Upper
3/8 9.5 100 100
4 4.75 70 90
8 2.36 45 70
16 1.18 28 50
30 0.6 19 34
50 0.3 12 25
100 0.15 7 18
200 0.075 5 15
The gradation adopted is as per Type III (Recommended Performance Guidelines for Emulsified
Asphalt Slurry Seal, 2005 - A 105). The aggregate gradation was set at the quarry itself by adopting
suitable sieves (Fig 1: Aggregate Gradation achieved). It has been an excellent cooperation from the
quarry owner for making such adjustments in the process.
Fig 1: Aggregate Gradation achieved
4.3 Designing the emulsion
Designing the emulsion has been extremely challenging, due to the many variables in the process.
The emulsion specified is as per the Indian Standard, Table 4: Specifications of Emulsion for Micro
surfacing (IRC SP 81: Specifications for Slurry Seal and Micro surfacing, 2009). The emulsion
designed is using Synthetic latex.
Table 4: Specification for Emulsion for Micro surfacing
Requirement Specifications Method of Test
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Residue on 600 Micron
Sieve (% Pass), Max
0.05 IS 8887
Viscosity by Say bolt
Furol Viscometer at 25C,
Sec
20 - 100 IS 8887
Coagulation of Emulsion
at low Temp
Nil IS 8887
Storage Stability after 24
h (168 h), % Max
2 (4) IS 8887
Particle charge +ve IS 8887
Tests on Residue:
- Residue by
evaporation, % Min
60 IS 8887
- Penetration at 25C,
100g, 5 Sec
40 - 100 IS 1203
- Ductility at 27C, cm,
Min
50 IS 1208
- Softening Point, C, Min 57 IS 1205
- Elastic Recovery, % Min 50 IS 15462
- Solubility in
Trichloroethylene
97 IS 1216
The final mix design is given below in tables 5 and 6. Cement is used as the mineral filler in the mix.
Table 5: Mix Design Ratio
Aggregates, % 100
Cement, % 2
Added Water, % 10
Emulsion, % 13
Table 6: Properties of Designed Mix
ISSA Test No Description Specification Values
ISSA TB 139 Wet Cohesion 30
Minutes Min (Set)
12 kg cm Min 18 kg cm
Wet Cohesion 60
Minutes Min
20 kg cm Min 33 kg cm
ISSA TB 114 Wet stripping Pass (90% Min) Pass
ISSA TB 100 Wet Track
Abrasion Loss,1
hr soak
807 g/m2 550 g/m2
ISSA TB 113 Mix Time 180 sec Min 180 Sec
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4.4 Execution:
There were many challenges faced during the execution of the micro surfacing. Frequently, even a
short blockage of traffic lead to large-scale discontent amongst commuters. The work had to be
compulsorily done in the night hours, which reduced the working window to between three and four
hours in a working shift. Therefore it was imperative that the emulsion set within one hour. The time
required for setting of emulsion also depends upon humidity as well as the ambient temperature. As
the temperature and humidity were in the extremes during the project, a continuous monitoring and
fine-tuning of emulsion chemistry was necessary. The huge success of the project has largely been
achieved by ensuring that the right emulsion has been used for the climatic and aggregate
variations. The average time taken to open the traffic on the freshly laid Micro-surfacing pavement
has been 1 hour.
4.4.1 Surface preparation
Any depressions in the surface were filled with a cold mix asphalt of appropriate grading suitable to
the depth of the depression and any visible cracks were repaired before applying the micro
surfacing. Severely cracked portions were removed and laid with cold mix prepared at site using
medium setting emulsions. The surface was cleaned by mechanical / power broom effectively before
application of the micro surfacing.
4.4.2 Calibration of Machine
In micro-surfacing works, the mix design is based upon the combined mass of dry aggregate and the
mass of mineral filler. To set the machine to a given mixture design and to produce a consistent
micro surfacing, accurate information on the delivery rates of the aggregate, emulsion, water and
mineral filler (cement) are necessary. A correction for natural moisture content in the aggregate is
also necessary for the mixture design. The Micro surfacing machine was thus frequently calibrated
for flow of aggregates, water, mineral filler (cement) and emulsion.
5. Regulation
National Highways Authority of India (NHAI) took note of this emerging technology in India and
studied the performance closely on various sections of pavement, which had been treated with micro
surfacing. Evaluation reports produced by the Central Road Research Institute (CRRI, 2005) helped
the NHAI to identify the benefits of this technology. Major conclusions of the various studies were:
- Need for reconstruction can be delayed using a thin layer of micro surfacing as preventive
treatment.
- Micro surfacing could be an alternative to thin hot mix renewals in maintenance of urban roads in
environment friendly manner and to saves energy.
- Only a marginal increase in pavement heights
- Faster laying process than HMA
- Effective quality control plays a vital role in success of a micro-surfacing projects
It is also indicated that Micro-surfacing treatment can fulfill the following different functions:
- Restores minor surface defects and acts as a protective layer. The inference drawn from the
experience and the data collected are as follows:
· One layer of micro-surfacing (7-8 kg/m2) brings down roughness values by about 200-300 mm/km,
which could be suitable mainly for preventive maintenance on structurally adequate pavement
· Two layers of micro-surfacing (15-16 kg/m2) help in reduction of roughness by 700-800 mm/km,
when used for periodic renewals in place of thin hot mix layer, provided roughness of original surface
is below 3000 mm/km. However, for periodic maintenance of surfaces with roughness over 3500
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mm/km, thickness of micro-surfacing needed will be around 12-14 mm, which can be achieved by
application of 28-30 kg/m2 of aggregate in multiple applications
In view of these established benefits, NHAI issued circular regularizing Micro surfacing treatments as
a preventive and periodic maintenance technique (NHAI, 2010).
6. Conclusions:
Road pavement maintenance and road pavement up grading are vital elements of road pavement
development and management programme. The fast growth in road pavement surface area offers
excellent growth potential for use of advanced technologies such as micro surfacing. Great efforts
have been made in co-ordination with local road authorities, and applicators to change the mind-set
of the markets and move to professional operations.
It is concluded that:
· Micro surfacing cannot rectify structural defaults, potholes and heavy rutting
· When the surface of existing pavement is uneven, the surface of single layer micro surfacing
application is also uneven. Experience shows that two-layer application has been successful over
cracked and patched surface.
· Environmental advantages
· No increase in road level due to thin layer application.
· Provide new friction and anti-skid resistance to the network
· Provide a protection sealing for the road surface and bridge-deck from water permeation. Restores
the surface condition and waterproofs the surface layer
· Emulsion chemistry allows a fast opening to traffic (minimal traffic interruption)
References:
Central Road Research Institute, Evaluation and Improvement Measures for Selected Roads of NDMC,
2005
Indian Road Congress, IRC 81 – 1997, Tentative Guidelines for Strengthening of Flexible Pavements
Using Benkelman Beam Deflection Techniques
Indian Road Congress, IRC SP 81 – 2009: Tentative Specifications for Slurry Seal and Micro surfacing
International Slurry Surfacing Association, Recommended Performance Guidelines for Emulsified
Asphalt Slurry Seal, A 105, 2005
National Highways Authority of India, Policy Matters – Technical, 2010
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