White Topping Report

8/10/2019 White Topping Report

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Table of ContentsChapter 1 ......................................................................................................................................................................................... 1

INTRODUCTION ........................................................................................................................................................................... 1

1.1 Background ............................................................................................................................................................................. 2

Chapter 2 ......................................................................................................................................................................................... 4

LITERATURE REVIEW ............................................................................................................................................................... 4

2.2 Studies On White Topping ................. ................ ................. ................ ................. ................ ................. ............... .......... 5

2.3 The procedure to be adopted for Implementing Whitetopping as Maintenance Strategy ............... .... 6

2.4 Advantages of White Topping ............... ................. ................ ................. ................ ................. ................ ................ .... 7

2.5 Scenario of Whitetopping ................ ................. ................ ................ ................. ................ ................. ................ ............ 8

2.6 Comparisons of Rigid And Flexible Pavement ............... ................ ................ ................. ................ ................ ....... 8

Chapter 3 ...................................................................................................................................................................................... 10

DESIGNING AND CONSTRUCTION OF ULTRA THIN WHITETOPPING ............... ................ ................. .............. 10

3.1 Design Procedure ................ ................ ................. ................ ................. ................ ................ ................. ................ ......... 10

3.2 Construction Procedure ................ ................. ................ ................. ................ ................. ................ ................ ............ 10

3.2.1 Surface Preparation ...................................................................................................................................................... 10

3.2.2 Placing ................................................................................................................................................................................ 11

3.2.3 Finishing and Texturing ............................................................................................................................................. 12 3.2.4 Curing ................................................................................................................................................................................. 12

3.2.5 Joint Sawing and Sealing ............................................................................................................................................ 12

3.3 First UTW Project in Kentucky .............. ................. ................ ................. ................ ................. ................ ................ . 13

3.4 Factors Affecting UTW Performance ................ ................. ................ ................ ................. ................ ................ .... 14

3.5 Repair of UTW ................. ................ ................ ................. ................ ................ ................. ................ ................. .............. 14

3.6 Concrete Mix Design ................ ................ ................ ................. ................ ................ ................. ................ ................ .... 16

3.7 Life Cycle Cost Analysis ............... ................ ................. ................ ................ ................. ................ ................ ............... 16

3.8 Advantages of UTW ............... ................. ............... ................. ................ ................. ................ ................ ................ ....... 17

3.9 Disadvantages of UTW ............... ................ ................ ................ ................. ................ ................. ............... ................. . 17

Chapter 4 ...................................................................................................................................................................................... 18

CONCLUSIONS ............................................................................................................................................................................ 18

REFERENCES .............................................................................................................................................................................. 19


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WHITETOPPING A Viable and Sustainable Option for Rehabilitation of roads

Department of Civil engineering, RVCE Page 1

Chapter 1

INTRODUCTIONRoad traffic is increasing steadily over the years. This is an international phenomenon. An

international forecast predicts that such increase will continue in near future. Even in case of

developed countries, there is a shortage of funds required for new infrastructure projects, both

for constructing them and more significantly towards their maintenance and repairs. The

position in the context of a developing country like India is obviously far worse.

The increasing truck weights and tyre pressures on our pavements in recent years have

pushed the demand on the performance of our pavements to a higher level. Many asphalt

pavements have experienced rutting while many others have experienced longitudinal

cracking. As a result, more and more roads are deteriorating and the existing pavement

structure as a whole is often found to be inadequate to cope up with the present traffic[1].

The cost of strengthening and repair by Conventional method of this large network will need

huge resources both physical and financial which are quite scarce.

Most of the existing flexible pavements in the network broadly have thin bituminous layers.

These bituminous pavements, in general, have a problem that they get deteriorated with time.

Most of our roads exhibit, in general, the following deficiencies: Rutting

Fatigue cracking

Block crack (D-cracking)

Thermo cracking

One of the possible solutions to this problem is the use of whitetopping (WT), which is a

cement concrete layer placed over an existing asphalt pavement. Ultra Thin White Topping

(UTWT) and Thin White Topping (TWT) are being increasingly practised in USA andWest Europe. Whitetopping is stronger than asphalt overlay, and thus more resistant to

rutting and surface-initiated cracking. Consequently, whitetopping pavements pose

potential economical and technical benefits. However, they need to be effectively

evaluated for feasibility and proper application techniques, suitable for India, so that their

use can provide the maximum benefits to the road users in particular and Indian economy

at large.Ultra-Thin Whitetopping is an emerging and innovative technology for asphalt

pavement


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rehabilitation in India. The concrete overlay utilizes closely spaced transverse and

longitudinal joints to reduce tensile stresses caused by traffic loads and environmental

conditions such as thermal stresses and curling due to temperature changes[2].

1.1 BackgroundConcrete Roads were first built by Romans (300 BC 476 AD). They were quite innovative

in the construction with the use of innovative materials viz., use of `Pozzolana cement from

the village Pozzouli near Italy, horse hairs as fibres in concrete, admixtures in their primitive

form (like animal fat, milk & blood). These roads, scientifically designed and constructed had

a long life and thus lead to the adage all (con crete) roads lead to Rome [3].

By the mid- 1950s, continuously reinforced concrete pavements (CRCP) started to gain in

popularity because the design offered the benefit of eliminating joint distress. The cost of the

steel in CRCP was expansive, and so, to be competitive, CRCP was built 25 to 50 mm

thinner, leading to premature distress. (The justifications perpetuated for using thinner

structural slabs are many but are primarily related to comparisons of deflections with jointed

pavements that had poor load transfer between slabs).

Also in 1950s, the slip form paver came into use. It reduced paving trains from 100 workers

down to about 25. Also the economics changed in that materials became cheap and labour

was more expansive. Hence, this led to a return to uniform thicknesses that could be easily

placed by the early slip forms [4].

Prestressed concrete was introduced in the late 1940s and was first used in airport

paavements. About 1959, two-way prestressed slabs were used at Biggs military airfield in

Texas. The 24-in (610 mm) plain pavement was replaced with 9-in (230 mm) post tensioned

slabs. Unfortunately the fear of the unknown, the need to use more skilled labour, and the

reluctance of mile-a-day slip from contractors to embrace this unproven technology have held

this concrete saving technology back. About a dozen highways with prestressed concrete

pavements of various designs were built in the United States between 1970 to 1990 [4].


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Table 1 UTW PROJECTS IN INDIA

According to National Cooperative Highway Research Program (NCHRP) Synthesis of

Highway Practice 99, the first recorded use of whitetopping in the United States was in Terre

Haute, Indiana. On this project, constructed in 1918, a 75 to 100mm jointed reinforced

concrete overlay was put in place . According to McGhee (1994), from 1918 to 1992,

approximately 200 white topping projects were done. Among them, 158 were jointed plainconcrete pavement, 14 continuously reinforced concrete, 10 fibre-reinforced concrete, and

seven were jointed reinforced concrete pavement [5]. Construction of white topping is not

limited to the U.S. only. Other countries including Belgium, Sweden, Canada, Mexico,

Brazil, the Republic of (South) Korea, Japan, F Austria, and the Netherlands [6] have

undertaken recent projects with white topping (Rasmussen and Rozycki, 2004). Agencies are

widely expected to use white topping as it is a cost-competitive technique, can be constructed

with minimal interruption of the travelling system, as well as be a means of greenconstruction compared to asphalt concrete overlay. Ultra-thin whitetopping overlay

technology has been started in India in 2003.Table show various UTW projects in India [7].

Year Location Thickness (mm)

2003 Pune ( In front of P.M.C Office) 125

2004 New Delhi ( CRRI campus road) 40-75

2006 Ghaziabad (Campus road of HRD centre) 50

2006 New Delhi (Meetha Pur, Badarpur) 125

2007 Mumbai ( Mahul Road) 100

2008 Thane ( In Gaotham Road) 125

2009 Pune ( Dahanukar Colony, Kothrud) 125


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Chapter 2

LITERATURE REVIEW

2.1 Performance Evaluation

D. R. Jundhare, Dr. K. C. Khare; and Dr. R. K. Jain conducted performance evaluation

studies to determine functional and structural condition of a whitetopping overlay which has

the purpose of routine monitoring or planning the corrective action. Following conclusions

are reached from the detailed study carried out using Benkelman Beam Deflection(BBD) as

per guidelines given in IRC: 81-1997, as Non Destructive Test(NDT) for determining

deflection at three critical load positions and Load Transfer Efficiency (LTE) has been

calculated at the transverse joints of 100 mm thick on in-service UTW overlay constructed in

Pune city, Maharashtra State (India), for its performance evaluation subjected to various

traffic and climatic conditions relevant to Indian scenario. The deflections obtained in this

study after two year is 0.461mm, 0.415 mm and 0.265 mm at the edge, corner and interior

respectively. These deflection results have been compared with the results of three

dimensional FE model (Jundhare D. R. et al., 2012), these values show good agreement. LTE

in the 100 mm thick UTW overlay for this study has been ranging from 88.03% to 100.00 %

in the 1.00 m x 1.00 m panel size. These results of LTE have been compared with the results

of 120 mm thick overlay (Cable, J. K. et al., 2006). LTE obtained for their study ranges from

99.60% to 99.90%. In another study, based on the finite element method using KENSLAB

computer program (Huang 1985) 84% of LTE value has been observed at transverse joint of

bonded type of interface. When results of BBD test from this study have been compared with

the deflection values obtained by three dimensional FE model (Jundhare D. R. et al., 2012)

and LTE values obtained by Cable, J. K. et al. (2006) as well as KENSLAB computer program, these values show good agreement. Therefore it can be concluded BBD is a useful,

reliable and alternative tool to Falling Weight Deflectometer(FWD) for the study of

performance evaluation of UTW overlay.

D. R. Jundhare, Dr. K. C. Khare; and Dr. R. K. Jain said Following conclusions are the model

in this study is a simple non-linear type developed by applying static axle loading. Through

the present study following conclusions have been drawn for the edge loading case, the

method of Westergaard gives stress 21.81 % and deflection 29.45 % more when compared


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with 3D FEM results. Comparison with ALIZE Method gives stress 2.09 % less. The

difference between the values from this method and the 2D modeling is due to the various

assumptions adopted in deriving these theories. It is revealed that, increasing the modulus of

subgrade reaction (k) of HMA resulted in reducing the stresses and deflections in plaincement concrete overlay. FEM analysis of the whitetopping shows stresses and deflection

induced in the whitetopping within the safe limits. Therefore unbonded plain cement concrete

overlays can be an economical and durable rehabilitation option, when the existing pavement

is severely deteriorated as compared to construction of conventional rigid pavement or HMA

overlay. This work confirms that the use of ANSYS software has a great potential as a

powerful tool for a 3D modeling of the conventional unbounded whitetopping.

D. R. Jundhare, Dr. K. C. Khare; and Dr. R. K. Jain said Following conclusions are reached

from the detailed study carried out using BBD as per guidelines given in IRC: 81-1997 and

FWD test as NDT for determining deflection at edge and corner load positions of 320 mm

thick on in-service conventional whitetopping overlay constructed in Pune city, Maharashtra

State (India), for its performance evaluation and correlation development subjected to various

traffic and climatic conditions relevant to Indian scenario. The linear, exponential and

logarithmic relationship has been developed using Benkelman Beam and FWD deflection

values on conventional whitetopping overlays. Among of the linear, exponential and

logarithmic relationships; the exponential relationship gives high R value. R 2 value of the

three relationships, it is higher in edge loading position than corner loading position. The

relationships developed are quite fair as R2 values are in between 0.65 to 0.80 which shows

the good correlation strength between the BBD and FWD deflection values .

The literature studies has helped us understand the pavement rehabilitation by white topping,

performs relatively well as compared to the conventional bituminous concrete overlay which

has been practiced widely even with its higher maintenance cost and lesser durability [8].

2.2 Studies On White Topping. There has been a renewed interest in whitetopping, particularly on Thin White Topping

(TWT) and Ultra-Thin White Topping (UTWT) over Conventional White Topping. Based on

the types of interface provided and the thickness of overlay, classification is as follows:


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Conventional White topping which consists of PCC overlay of thickness 200 mm or

more, which is designed & constructed without consideration of any bond between

existing overlay & underlying bituminous layer (without any 1composite action).

Thin White topping (TWT) which has PCC overlay between 100 200 mm. It is

designed either considering bond between overlay & underlying bituminous layer or

without consideration of bond. High strength concrete (M 40 or higher) is normally

used to take care of flexure requirement. Joints are at shorter spacing of 0.6 to 1.25 m.

Ultra-Thin White topping (UTWT) which has PCC overlay of less than 100 mm.

Bonding between overlay & underlying bituminous layer is mandatory . To ensurethis, the existing layer of bitumen is either milled (to a depth of 25 mm) or surface

scrapped (with a non-impact scrapper) or gently chiseled. Joints are provided at a

spacing of 0.6 to 1.25 m [3].

Figure: 1 Conventional (No Bond) V/s Ultra-Thin White Toping (Bond is there)

2.3 The procedure to be adopted for Implementing Whitetoppingas Maintenance Strategy Design life--should be at least 15 years; 25 to 30 years is often projected for city streets.

Cost alternatives--define initial construction costs, maintenance costs, and the design life

of the topping.

Drainage considerations - define the elevation of crown sections to ensure good drainage.

Pavement patching--identify areas that require sub grade repair after the milling operation

Thickness design--considers the thickness of the asphalt pavement, the thickness of the


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topping, traffic loads, and panel layout.

Longitudinal and transverse joints--determine joint spacing by the overlay pavement

thickness and the geometrics of the area to be paved. Normal practice is to saw the joints

in the new pavement; tooled joints are also permitted for some areas. Profile correction--determine joint spacing by the thinnest concrete profile and carry this

spacing throughout the project.

Surface texture--texture is specified in relation to the speed of traffic. Drag (burlap or

boom) textures are good for low-speed facilities; high-speed facilities should use more

aggressive textures.

Traffic control--traffic can be detoured, shifted, or otherwise accommodated during

construction, but there must be a plan before construction starts.

Construction staging--stage the construction to cause the least disruption [9].

2.4 Advantages of White Topping Reduced thickness due to thickness of overlay remaining constant for over 2

decades.

Fast-Track construction making use of innovations in concrete technology & batch

mixing, concretes can be designed to have 3 days compressive (& flexural) strength,

so as to open the road for traffic within 5 days of construction.

Reduced maintenance as the concrete overlays live for over 2 decades, with least

maintenance.

Cost-effective compared to asphalt overlays when Life Cycle Cost is taken into

consideration.

Improved service life with better riding quality, improved fuel efficiency of

vehicles.

Little pre-overlay repairs.

Improvement in safety in view of the increased reflection of light particularly on

city roads, it would save 24 % less electricity compared to flexible pavements.

Reduction in operational costs and lower absorption of solar energy.

Improving the environmental benefits as concrete roads are much greener and less

polluting.


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2.5 Scenario of WhitetoppingBase: Most of the existing, worn asphalt pavement is left in place and serves as a base. Ruts

in the asphalt are milled down to start with a clean level surface. Ultra-thin white topping

(UTW) should not be placed over asphalt pavement that shows signs of deep pavementdistress. If potholes, alligator cracking, or deep fissures exist in the asphalt, the concrete will

not form an adequate bond, resulting in pavement that lacks adequate support. Asphalt

pavement should be at least 3-inches thick to provide a sufficient base for UTW.

Many installers mill off the amount that will be replaced by the UTW so that they dont

change the surface grade. White topping can be placed using conventional paving

equipment.

Joints: Joint spacing is critical to a good performing UTW project. Successful projects

use a short joint spacing to form, in effect, a mini-block paver system. Experience

indicates that joint spacing should be no more than 12 to 18 inches each way per inch

of white topping thickness. For example, a 3-inch UTW surface should be jointed into

3x 3 or 4x4 foot squares. Joints are sawed early to control surface cracking [10].

2.6 Comparisons of Rigid And Flexible Pavement

Flexible pavements are the conventional asphalt/bituminous concrete pavements whereas

rigid pavements are cement concrete pavements. In asphalt pavements grain to grain transfer

of load takes place, where as in cement concrete pavements layer to layer transfer of loads

takes place.

Asphalt pavements consists of sub grade, granulated sub base, base and bituminous concrete

layers. Whereas the rigid pavements subgrade and base layers.

Rigid Pavement Flexible Pavement

Figure: 2.1 Comparisons of Rigid and Flexible Pavement


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T able 1 COMPARISION OF RIGID AND FLEXIBLE PAVEMENTS

Comparisons Rigid Flexible Strength High Low

Cost High Low Noise level Low High Safety More Less Environmentally friendly Yes No Ride Smooth Rough Life span More Less Maintenance Less More Heat Reflection Less More

2.7 Advantages of Rigid Pavement compared to Flexible Pavement

Longer life cycle of the pavement structure

Slow rate of deterioration

Surface deficiencies could be corrected

Improve skid resistance of the pavement

To improve ride quality (restores crown)

Very smooth riding surface

No excess stone build ups

No broken windshields from loose aggregate

Ease of construction, use standard paver

Minimal construction time

Dont have to adjust structures


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Chapter 3

DESIGNING AND CONSTRUCTION OF ULTRA THIN

WHITETOPPING3.1 Design ProcedureFollowing UTW design procedure is adopted:

1) Based on traffic data number of equivalent axle loads are obtained. The elastic

modulus and thickness of the existing asphalt pavement are also obtained.

2) Allowable tensile stress in asphaltic concrete has been calculated.

3) Thickness for UTW is assumed. Maximum tensile stress in allowable compression

due to UTW for both bound and unbound conditions are found out.

4) Maximum tensile stress in allowable compression is compared with the allowable stress

5) Maximum tensile stress in UTW due to both axle load and temperature

differentials has been calculated.

6) Stress ratio in UTW is obtained and Maximum allowable load repetitions are determined.

7) If the UTW fatigue criterion indicat es a small number of ESALs, the n UTW thickness

increased and repeat the steps 4 to 6 [11].

3.2 Construction Procedure

3.2.1 Surface Preparation

A clean surface is required for proper bond. Milling the surface followed by cleaning

improves bond because it exposes more of the aggregate of the asphalt pavement. The

milling creates a rough surface that also enhances the bond between the two layers. Ifmilling is not done, water or abrasive blasting should be used to clean the asphalt

surface. When water blasting is used, the surface must be allowed to air dry before the

concrete is placed.

Once a surface is cleaned, it is important to keep it clean until the concrete overlay is

placed. Dust, dirt and debris that falls or blows onto the asphalt surface must be

removed as shown in figure 3.1. If the surface is cleaned on the day prior to paving, air

cleaning may be required on the day of paving to remove dirt and dust. If the traffic is


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allowed on the milled surface, the surface must be re-cleaned prior to paving [12].

Figure: 3.1 Surface preparation

3.2.2 PlacingAfter surface preparation, there must be enough asphalt remaining to form a sufficient

composite section that can carry the load. There must be enough asphalt to minimize

concrete tensile stresses, and enough concrete to minimize asphalt strains. It is

recommended that the minimum asphalt thickness after milling exceed 3 inches.

Paving UTW isnt any different than paving any other concrete pavement.

Conventional slip-form and fixed-form pavers as shown in figure 3.2, as well as small

equipment - such as vibrating screeds - have all been used successfully, without major

modifications.

Figure: 3.2 Spreading and leveling of UTW over prepared pavement


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3.2.3 Finishing and TexturingTypical concrete finishing and texturing procedures are appropriate for ultra-thin white

topping. Texturing of the finished UTW pavement surface is required to provide

adequate surface friction of the roadway. Surface friction is provided by carpet drag or brooming, which also reduces noise as shown in figure 3.3.

Figure: 3.3 Finishing and Texturing

3.2.4 CuringProper curing is critical to avoiding shrinkage cracking in the concrete overlay and to

prevent de-bonding between the asphalt and concrete. Because the overlay is a thin

concrete slab, it has high surface area to volume ratio and can lose water rapidly due toevaporation. Curing UTW is similar to curing new PCC pavements. It requires curing

the entire pavement surface and edges as soon as surface conditions permit after the

finishing operations using either blanket or membrane methods. The most common

practice is to spray liquid, a membrane curing compound.

3.2.5 Joint Sawing and SealingSawing is critical to avoid random cracking in white topping. Partial-depth saw cutting

operations should commence immediately after the concrete has gained enough

strength to prevent ravelling and spalling of the joint

Joints should be sawed with lightweight saws as early as possible to control cracking.

Saw-cut depth should be 1/4 - 1/3 of overlay thickness as shown in figure 3.4.

Typically, the joints are not sealed. They have performed well without sealant because

the short joint spacing minimizes joint movement. Performance to date shows no

benefit from sealant use [13].


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Figure: 3.4 Joint Sawing and Sealing

3.3 First UTW Project in Kentucky

The first high- profile UTW project in the United States took place in Louisville, Kentucky,in 1991. I was a landmark in UTW history, demonstrating that ultra thin whitetopping 50 to

90 mm can carry traffic loads typical of many low volume roads, residential streets, and

parking lots [14]. The pavement section served as an access road to a disposal facility, which

was selected to provide performance data on a common distress and failure modes of UTW

overlays that are subjected to heavy loads similar to those of garbage trucks. The accessed

roads serviced 400 to 500 trucks 5 days in a week. This was viewed as a suitable site for the

accelerated testing of the UTW pavement, as the truck loading was 20 to 100 times greaterthan that on an average low volume road. The significant findings from the Louisville UTW

experiment were that the bond between the UTW and the existing HMA pavement

significantly reduced the stresses in the concrete section. This allows the section to perform

as a composite section, corner cracking was the predominant distress and joint spacing has a

significant effect on the rate of corner cracking. The success of this project led to a number of

different projects in other states including Georgia, Virginia, Florida and Lowa [15]

Thin concrete overlay has been used in increasing numbers over hot-mix asphalt (HMA)

pavements and at intersections as a rapid and economical method of repair. These repairs

have shown outstanding services in the state of Oklahoma with service lives over 10 years

when used in areas with moderate truck traffic [16]


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3.4 Factors Affecting UTW Performance a) Concrete Mixture Proportions

b) Typical Construction Procedures adopted

c) Traffic loading on the pavements

d) Pavement Monitoring and maintenance

3.5 Repair of UTWWhen to repair

Generally, repairs should be considered when:

Panels are broken into four or pieces

Surface irregularities or settlement affect ride quality

Loose or missing concrete is evident

Repair procedures

The repair of UTW pavement involves locating and replacing deteriorated panels. Because

UTW joint spacing usually creates small panels, the removal and replacement of concrete is

very simple.

There are six steps involved in repair of UTW:

1) Identify the panels to be removed.

2) The damaged panel is saw cut to the perimeter and to full depth of concrete.

3) The damaged concrete panel and any deteriorated asphalt pavement beneath is removed

completely.

4) The area to be corrected is well prepared and patched accordingly.

5) Place, finish, and cure the new concrete.

6) Saw the joints for lateral and longitudinal expansions which takes place during summer

and open the stretch to traffic.

Identify and isolate slabs to be removed

The first step in the repair process for UTW is to determine which panels need to be

replaced. The panels are usually identified with bright colored paint .cracks in panels

do not require repair, but if the UTW overlays breaks up begins moving or dislodging,

repairs are warranted. The entire panel containing the distress should be removed and

replaced.


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Saw cut panels to bottom of concrete overlay

The distressed panel should be cut at all joint lines using diamond or abrasive-bladed

saws to the bottom of the concrete overlay. Care should be taken not to damage the

underlying asphalt layer. Full-depth sawing to the bottom of the concrete overlayresults in clean cuts, easy removal of the deteriorated concrete, and less joint spalling.

Remove panels

There are two ways to remove the deteriorated

concrete: 1. Break up 2. Full panel removal

To break up the concrete, jackhammers are used. Care must be taken not to damage

the adjacent panels with any equipment during removal process.

Prepare patch area

Before concrete placement, the asphalt surface should be cleaned by air blasting with

clean, compressed air. Sand or shot blasting is required if air blasting will not remove

foreign material from the surface. The asphalt surface must be kept clean prior to the

placement of new concrete.

Place new concrete

The placement of new concrete into the patch areas of the UTW pavement should follow 6

steps:

Place the concrete into repair areas

Consolidate the concrete using a hand held vibrator

Finish with a straight edge or vibratory screed to meet the existing Grade

Texture the concrete surface to match the surrounding panels

Apply curing compound immediately after the bleed water sheen disappears

Cover with insulating blankets if the ambient temperature falls below about 5 degree

centigrade within 24 hours of placement

Saw joints and open to traffic

Saw joints as soon as possible without revelling the concrete to match the width and location

of existing and adjacent joints. The repaired pavement can be open to traffic once the

concrete has reached the specified opening strength, maturity or curing time [17].


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3.6 Concrete Mix Design

The type of concrete mix for a particular UTW project is often selected based on traffic

conditions, concrete strength and time requirements for opening to traffic.Many UTW projects have utilized fast track concrete mixes that typically contain

higher cement content or high early-strength cement. In addition, fast track mixes can

be adjusted to produce compressive strengths of at least 20 MPa in 24 hours and 28-

day strengths in excess of 40 MPa.

Synthetic fibres are often used in UTW mixes to provide additional strength and durability to

the thin concrete layer. It has also been found that these fibres extend the time window for

saw-cutting the joints by delaying early plastic shrinkage cracking.

3.7 Life Cycle Cost AnalysisA recent life cycle cost (LCC) analysis study was conducted in British Columbia to

evaluate the relative effectiveness of Ultra-Thin Whitetopping versus traditional asphalt

rehabilitation of deteriorated or rutted asphalt intersections. The study evaluated 150

intersections in the City of Surrey, B.C. for cost effectiveness of competing

rehabilitation strategies using five different life cycle costing philosophies. They are:

1) Maximizing the net Road User Cost savings

2) Comparing direct agency costs to Road User Cost savings

3) Minimizing an agencys direct agency costs

4) Maximizing the resulting pavement quality

5) Comparing direct agency costs to resulting pavement quality

Cost effectiveness of UTW depends on existing asphalt thickness, amount of truck

traffic, base and sub grade support conditions, and pavement condition. The most

important factors are the existing asphalt thickness and amount of expected truck

traffic.

The LCC study in Surrey, BC shows that UTW rehabilitation is extremely dependent

on site conditions and traffic volume. If a particular site does not have the required

minimum thickness of asphalt and a fairly high volume of truck traffic that will cause

rutting of the asphalt, UTW may not be the most cost effective alternative for repair.

However, if the site conditions do warrant UTW rehabilitation, the benefits can be

substantial[18].


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3.8 Advantages of UTW Economical cost moderately less than that of conventional asphalt surfacing

High standard of surface texture giving good skid resistance and reduced water spray

Reduced noise levels compared to dense-graded asphalt and sprayed seals

Good ride qualities

Flexible and tolerant to surface deflections

Assists waterproofing of the underlying surface

Thin layer reduces the need for cold planning, etc. to match adjoining surfaces. No

loose aggregate such as in a spray seal

3.9 Disadvantages of UTW Higher cost than sprayed seal

Effective treatment may require preliminary regulation and SAMI treatments

Low shear resistance may make it unsuitable in areas of high shear forces

Hence the literature studies has helped us in the technical understanding and the methodology

involved in the design procedure of UTW and also the process or methodology involved inthe construction of UTW.


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Chapter 4

CONCLUSIONS

White topping has emerged as a fast growing technology for pavement rehabilitation.

White topping has emerged as a fast, competitive remedy for rutted asphalt

pavements rehabilitation by offering the enhanced performance and durability of

concrete.

White topping overlays are bonded to existing asphalt to create a composite section,

resulting in improved performance and durability at a lower cost.

Ultra Thin White topping develops the required strength for opening to traffic in as

little as 24 hours.

In order to help state highway agencies and contractors better design and apply the

UTW, well-controlled pavement response and performance data is needed to improve

and refine the existing UTW design procedures.

Positive impact on reducing CO 2 emissions resulting from the manufacturing and

placement of paving materials.

Based on the advantages and a lesser maintenance cost of white topping it could be

concluded that rehabilitation of an asphalt pavement by white topping is a viable and

sustainable technique compared to the bituminous concrete overlay.


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REFERENCES

1. Mitesh D. Patel, Prof. P.S. Ramanuj, Bhavin Parmar, Akash Parmar , White topping

as a rehabilitation method: a case s tudy of budhel-ghogha road . IJAERS/Vol.

I/ Issue IV/July-Sept., 2012/31-35 E-ISSN2249 8974.

2. D. R. Jundhare, K.C. Khare, and R.K.Jain, Ultra-Thin Whitetopping in India: State-of

Practice ACEE Int. J. on Transportation and Urban Development, Vol. 2, No. 1,

April 2012.

3. Dr. V. Ramachandra, WHITETOPPING A Viable & Sustainable Option for

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Documents

White Topping Report