Highway Maintenance

By:Dr. M. Parida

DEPARTMENT OF CIVIL ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY ROORKEE

ROORKEE – 247 667

IMPORTANCE OF HIGHWAY MAINTENANCE WORKS

Different types of damages of roads during Rainy season are:

• The unlined road-side drains may get eroded during heavy down pour of rains.

• The earth shoulders of the highway may be eroded between the pavement edge and the

shoulders resulting in formation of ‘edge drop’, this leads to (i) inconvenience and danger to

traffic (ii) reduction in roadway capacity and (iii) rapid deterioration of the edges of the

pavement structure.

• The soil from the road-side may get deposited along the edges resulting in ineffective cross

slope and stagnation of water along the pavement edge.

• Part of the rain water that percolates though the pavement layers and shoulders may damage

or weaken the pavement layers at some road stretches.

• Heavy rains also causes silting up of catch pits and under-ground drains , damage to foot

paths, cycle tracks and other pedestrian facilities.

Pavement Deterioration – Causes and types of deterioration

• Pavement deterioration takes place due to the combined action of traffic, weather changes,

drainage, environmental factors, etc.

• Flexible pavements generally deteriorate at a more rapid rate when compared to rigid

pavements due to the above mentioned factors.

• Flexible pavements continue to deterioration at a slow rate even without the traffic

movement on the surface, due to the climatic and environmental factors.

• rate of deterioration of bituminous pavement increases rapidly when water is retained in the

void spaces of the bituminous pavement layers.

• Aging and oxidation of bituminous binder lead to the deterioration of bituminous surfacing.

Two types of deterioration take place in highway pavements

(i) functional deterioration and (ii) structural deterioration.

Functional deterioration of pavements

Due to combined action of traffic, climatic and environmental factors, predominantly on the

surfacing course of the pavement.

The physical forms of functional deterioration of flexible pavements include,

(i) formation of pot-holes, reveling and cracks at some locations

(ii) formation of undulations or unevenness including depressions along the longitudinal

profile of the pavement surface

(iii) formation of longitudinal ruts along the wheel paths

(iv) shoving of pavement or plastic movement within the layer resulting in localized bulging of

the surface.

(v) the pavement surface getting polished or very smooth, particularly along the wheel paths

and becoming slippery under wet condition

(vi) formation of large waves along the longitudinal profile which affects high speed travel

Functional evaluation of pavements

Unevenness Index

Present Serviceability Rating and Present Serviceability Index

Unevenness Index : The cumulative value of pavement surface undulations per unit length of

the road along the longitudinal profile is expresses in terms of ‘unevenness index’ or roughness

index.

Unevenness is measures by Bump Integrator: (a) The trailer type bump integrator comprises of

a single automobile wheel with rubber tyre mounted on heavy chassis and suspension system.

(b) This trailer unit is hauled along the road surface by a tractor unit at uniform speed of 30

kmph and the integrator unit gives the cumulative value of pavement undulations.

Unevenness index generally expressed as mm/km or m/km length of the road.

As per IRC guidelines, a bituminous concrete surface of a highway is considered to be

• Good if (UI) is less than 2000 mm/km

• Poor when (UI)exceeds 3000 mm/km.

Similarly in the case of thin bituminous surfaces like premix carpet or mix seal surfacing, UI

value of 3000 mm/km is considered to be good and values exceeding 4000 mm/km as poor,

justifying resurfacing.

Pavement evaluation by ‘Present Serviceability Rating’ and ‘Present Serviceability Index’

Assessment of the road condition is done by a panel of road users in a ‘rating scale’ of 0 to 5

and the average rating numbers is designated as ‘Present Serviceability Rating’ or PSR.

In the opinion of the road users if a particular road stretch is ‘very good’, a rating of 4 to 5 is

awarded; similarly a ‘good’ pavement is awarded 3 to 4, ‘fair’ 2 to 3, ‘poor’ 1 to 2 and ‘very poor’

0 to 1.

The PSR values are subjective and awarded by a panel of trained rating personnel for

different pavement stretches these have been correlated with the objective measurements. The

regression equation developed during the ‘AASHO Road Test’ studies is in the form given in the

equation below:

PSI = A0 + A1 ( R ) + A2 (F1) + A3 (F2) (Eq.

1)

where,

PSI = Present Serviceability Index

A0, A1, A2, A3 = constants of regression analysis

R = measure of roughness or unevenness F1, F2 = physical measurements of cracking, etc.

The Present Serviceability Index (PSI) helps in rating of pavements based on a common set of

rating norms. Often a PSI value of 2.5 is considered as a terminal value of a pavement needing

immediate attention.

Structural deterioration of pavements

The main cause contributing to structural deterioration of pavement is due to repeated

application of heavy traffic wheel load, the rate of structural deterioration affects the service life

of the pavement.

The structural deterioration gets accelerated due to entry of water into the pavement layers

including the subgrade.

Structural deterioration of flexible pavements

In the case of flexible pavements, the structural deterioration is indicated by :

(i) increase in the magnitude of pavement deflection under a standard wheel load and

(ii) increase rut depth on the pavement surface which indicates the permanent deformation of

the pavement layers including the subgrade along the wheel path of heavy vehicles

Objectives of Highway Maintenance• to provide safe and convenient travel facilities to the road users

• avoid detour, speed changes, etc. due to failures in roadway facilities

and to minimize the increase in road transportation cost

• preserve the asset and investments made on the road infrastructure

by taking appropriate maintenance measures at the right time.

• avoid rapid deterioration of the pavement structure leading to huge

maintenance cost by carrying out timely ‘preventive maintenance’

works.

• To improve the pavement surface or structural condition by providing

resurfacing layer or strengthening layer, at the right time so as to

extend the life of the existing pavement structure

• To preserve the surrounding environment and natural aesthetics so

that the travel road is pleasant and comfortable.

Table 29.1 : Recommended Roughness Values for Roads in India(mm/km Measured on Towed Fifth Wheel Bump Integrator)

Surface TypeRoad Condition

Good Average Poor Very Poor

1. Asphaltic concrete 2000-2500

2500-3500

3500-4000

Over 4000

2. Premix open texturedbituminous carpet

2500-4500

4500-5500

5500-6500

Over 6500

3. Surface dressing 4000-5000

5000-6500

6500-7500

Over 7500

4. Water-bound macadam or gravel

8000-9000

9000-10000

10000-12000

Over 12000

Table 29.2 : Serviceability Indicators for India Highways

S.No. Serviceability Indicator

Level 1 (Good) Level 2 (Average) Level 3

(Acceptable)

1. Roughness by bump integrator (Maximum permissible) 2000 mm/km 3000 mm/km 4000 mm/km

2. Potholes/km (Maximum Numbers) Nil 2-3 4-83. Cracking and Patch repairs (Maximum

permissible) 5 percent 10 percent 10-15 percent

4.Rutting (20 mm) (Maximum permissible) 1.0 percent 1.5 percent 2.5 percent

5. Skid resistance (Skid number by ASTM-274) Minimum Desirable 50 SN 40 SN 35 SN

6. Defective bridge deck area and bump at approach (Maximum permissible) Nil 10 percent 15 percent

7. User information All road signs, km stones and road markings in good condition

Only major road signs, km stones, some road markings in good condition

Signs only for major destinations and km stones in fair condition.

Classification of Highway Maintenance Works

• Routine maintenance

• Preventive maintenance

• Periodic maintenance

• Special maintenance

• Emergent repairs

• Strengthening and rehabilitation – of road pavements and cross-drainage

structures

Needs for rectification of damages in road pavements

• Both functional and structural deterioration of pavement take place at different rates.

• The pavement condition is to be inspected at frequent intervals and different types of

pavement distress that may develop are to be rectified timely, as part of the maintenance

program me so as to provide the desirable level of comfort and safety to the road users.

Routine maintenance

The concerned maintenance staff shall carry out day-to-day site inspection of the designated

road stretches and note down the damages that have occurred due to natural or artificial

causes. They should take immediate steps to correct or rectify the damages. Some of the

items included under routine maintenance are

(i) clearing of blocked drains

(ii) restoration of surface drainage system including correcting cross

slope of earth shoulders

(iii) repair of rain cuts on shoulders and slopes

(iv) patching of pot-holes on pavement surface and

(v) repair of edge drop on the shoulders along the pavement edges.

Preventive maintenance of bituminous pavements

The residual life or service life of the bituminous pavement surface course can be increased by

taking certain ‘preventive maintenance’ measures at the right time. For example, if the

bituminous surface course has started developing fine cracks on the surface, the cracks may be

sealed with a simple and less expensive crack sealing treatment; a suitable type of ‘seal coat’ or

‘slurry seal’ may be applied at the appropriate time thus, the life of the surface course can be

extended by one or more number of monsoon seasons.

Patching the pot-holes and treating the cracked areas in a proper manner, as soon as they

develop at some locations on the pavement surface are also considered as part of the

preventive maintenance measures; this is because, if these pot-holes or cracked areas are left

unattended to even for a few days, the area and depth of deterioration will increase at a very

rapid rate due to the combined action of traffic, water and other environmental factors

Periodic maintenance

Periodic maintenance works such as resurfacing of pavements may be required to restore the

functional deficiencies that have developed over a time period.

There may be several cases where the flexible pavement stretches are functionally deficient, but

they are still structurally adequate. All these cases may further be divided into two categories,

(a) those not requiring a profile correction course : In case surface has developed only small

undulations of depth less than 40 mm and the cross slopes are satisfactory, it is not essential

to provide a separate profile correction course; it is sufficient to just improve the riding

quality by laying a resurfacing course. Therefore, first the locations with pot-holes and

isolated areas with wide cracks are properly cut and patched; then a resurfacing course of

thickness, say 40 mm is laid with a paver.

(b) those which require a profile correction course:

In the cases where; (i) the cross slope of the pavement needs correction and/or (ii) the

undulations are larger in size, a separate profile correction course is be laid by a paver, after

cutting and patching the pot-holes and isolated areas with wide cracks. This is followed by a

resurfacing course laid with paver.

In cement concrete pavements there is a need to periodically examine the joints and apply joint

sealing, where required. Also, the filler boards used at the expansion joints may need

replacement periodically, depending on the type of filler material used and the rate of

deterioration at the site.

The other components of the road such as abutments, cross drainage structures, earth

retaining structures, pavement marking and other traffic control devices need periodic

maintenance. These maintenance works are also undertaken under periodic maintenance

operations.

Special maintenance

Occasionally severe damages are caused to roads and cross drainage structures by floods

or heavy down pour of rains, though these may not occur every year. Under such

circumstances special funds are sanctioned to meet the cost f special repair and

maintenance works, as required.

Emergency repairs

During heavy monsoon season occasionally breaches of road stretches or landslides or

washing away of part of bridge structure do take place, particularly on hill roads. Under

such circumstances temporary diversions and emergent reconstruction works become

unavoidable in order to restore the traffic within the shortest possible time. The executive

engineer at the site will have to undertaken such works expeditiously in anticipation of

formal sanction of special maintenance grant.

Strengthening and rehabilitation of road pavements• If a flexible pavement on a particular road stretch needs strengthening, but the

strengthening work is not taken up on time, structural deterioration takes place at a rapid

rate on one or more of the top pavement layers; further delay may cause extensive

damages to the existing pavement layers that one or more of the damaged layers will

have to be carefully removed from the top without disturbing underlying layers and be

reconstructed. This is a partial removal and reconstruction of pavement layers and may

be categorized under ‘rehabilitation work’.

Further delay in carrying out rehabilitation work will result in extensive damages to most of

the pavement layers, necessitating ‘total removal and reconstruction’ of the entire

pavement structure.

Strengthening of rigid pavement is a more complex problem than strengthening of flexible

pavements.

Causes of distress in flexible pavements

• Ineffective road surface drainage system

• Blockages or silting up of longitudinal and cross drains resulting in stagnation of water

• Inadequate sub-surface drainage system or improper functioning of the drainage/GSB layer,

leading to stagnation of water on the subgrade or within any of the pavement layers and

resultant damages to the pavement layers.

• Environmental factors including heavy rainfall, soil erosion, high water table, snow fall, frost

action, etc.

• Inadequate compaction of embankment, subgrade or any of the pavement layers or

settlement of embankment foundation itself, which could result in settlement of the

supporting layers of the pavement resulting in damages to the roadway.

• Defects in construction method and quality control during construction.

• Defects in the quality of materials used in any of the pavement layers.

• Increase in the magnitude of wheel loads and the number of load repetitions.

General causes of distress in rigid pavements

• Defective drainage system may lead to failures in rigid pavements such as mud pumping,

unless preventive measures are taken up at the design and construction stages.

• Use of nondurable materials which start deteriorating during weathering cycles.

• Improper alignment of dowel bars may lead to stress concentration and cracking near the

joints.

• Structural inadequacy of the pavement structure consisting of the cement concrete (CC)

pavement slab, sub-base and subgrade, with respect the actual loading conditions to which

the pavement is being subjected to.

• Inadequate compaction of embankment or subgrade or settlement of embankment

foundation itself, which could result in settlement of the supporting layers of the rigid

pavement; these may lead to opening up of the joints or even non-uniform settlement of the

pavement slabs resulting in deterioration in riding quality.

Table 29.3 : Symptoms, Causes, and Treatment of Defects in Bituminous Surfacings

Type of distress(1)

Symptoms(2)

Probable causes(3)

Possible types of treatment

(4)

A. Surface defect1. Fatty surface Collection of binder

on the surfaceExcessive binder in premix, spray or tack coat; loss of cover aggregates, excessively heavy axle load.

Sand-blinding; open-graded premix; liquid seal coat; burning of excess binder; removal of affected area.

2. Smooth surface Slippery Polishing of aggregates under traffic, or excessive binder.

Resurfacing with surface dressing or premix carpet.

3. Streaking Presence of alternate lean and heavy lines of bitumen

Non-uniform application of bitumen, or at a low temperature

Application of a new surface.

4. Hungry surface Loss of aggregates or presence of fine cracks

Use of less bitumen or absorptive aggregates

Slurry seal or fog seal.

B. Cracks1. Hair-line cracks Short and fine cracks

at close intervals on the surface

Insufficient bitumen, excessive filler or improper compaction

The treatment will depend on whether pavement is structurally sound or unsound.

2. Alligator cracks Inter-connected cracks forming series of small blocks

Weak pavement, unstable conditions of subgrade or lower layers, excessive over-loads or brittleness of binder

Where the pavement is structurally sound, the cracks should be filled with a low viscosity binder or a slurry seal or fog seal depending on the width of cracks.

3. Longitudinal cracks

Cracks on a straight line along the road

Poor drainage, shoulder settlement, weak joint between adjoining spreads of pavement layers or differential frost heave

4. Edge cracks Cracks near and parallel to pavement edge

Lack of support from shoulder, poor drainage, frost heave, or inadequate pavement width

5. Shrinkage cracks Cracks in transverse direction or inter-connected cracks forming a series of large blocks

Shrinkage of bituminous layer with age

6. Reflection cracks Sympathetic cracks over joints and cracks in the pavement underneath

Due to joints and cracks in the pavement layer underneath.

C. Deformation1. Slippage Formation of

crescent shaped cracks pointing in the direction of the thrust of wheels

Unusual thrust of wheels in a direction, lack or failure of bond between surface and lower pavement courses

Removal of the surface layer in the affected area and replacement with fresh material.

2. Rutting Longitudinal depression in the wheel tracks

Heavy channelized traffic, inadequate compaction of pavement layers, poor stability of pavement material or heavy bullockcart traffic

Filling the depressions with premix material.

3. Corrugations Formation of regular undulations

Lack of stability in the mix, oscillations set up by vehicle springs, or faulty laying of surface course

Scarification and relaying of surfacing, or cutting of high spots and filling of low spots.

4. Shoving Localised bulging of pavement surface alongwith crescent-shaped cracks

Unstable mix, lack of bond between layers, or heavy start-stop type movements and those involving negotiations of curves and gradients

Removing the material to firm base and relaying a stable mix.

5. Shallow depression

Localised shallow depressions

Presence of inadequately compacted pockets

Filling with premix materials.

6. Settlement and upheaval

Large deformation of pavement

Poor compaction of fills, poor drainage, inadequate pavement or frost heave

Where fill is weak the defective fill should be excavated and redone. Where inadequate pavement is the cause, the pavement should be strengthened.

D. Disintegration1. Stripping Separation of bitumen

from aggregates in the presence of moisture

Use of hydrophilic aggregate, inadequate mix composition, continuous contact with water, poor bond between aggregate and bitumen at the time of construction, etc.

Spreading and compacting heated sand over the affected area in the case of surface dressing; replace-ment with fresh bituminous mix with added anti-stripping agent in other cases.

2. Loss of aggregate Rough surface with loss of aggregate in some portions

Ageing and hardening of binder, stripping, poor bond between binder and aggregate, poor compaction etc.

Application of liquid seal, fog seal or slurry seal depending on the extent of damage.

3. Revelling Failure of binder to hold the aggregates shown up by pock marks of eroded areas on the surface

Poor compaction, poor bond between binder and aggregate, insuffi-cient binder, brittleness of binder etc.

Application of cut-back covered with coarse sand, or slurry seal, or a premix renewal coat.

4. Pot-hole Appearance of bowl-shaped holes, usually after rain

Ingress of water into the pavement, lack of bond between the surfacing and WBM base, insuffi-cient bitumen content etc.

Filling pot-holes with premix material, or penetration patching.

5. Edge-breaking Irregular breakage of pavement edges.

Water infiltration, poor lateral support from shoulders, inadequate strength of pavement edges, etc.

Cutting the affected area of regular sections and rebuilding with simultaneous attention paid to the proper construction of shoulders.

Table 29.4 : Recommended Type and Periodicity of Renewals

Type of Treatment/ Category of Road

Traffic Intensity in CVD

MR-I SD-II PC + SC 20 mm MSS

25 mm SDBC

25 mm BC

40 mm BC

NH/SHs (Normal)

> 4500 --- --- --- --- --- 5/4* 5/4*

1500-4500

--- --- --- --- 5/4* 5/4* ---

450-1500 --- --- --- 5/4* 5/4* --- ---

< 450 --- --- 5/4* 5/4* --- --- ---

NH/SHs(Urban)

> 4500 --- --- --- --- --- 4/3* 4/3*

1500-4500

--- --- --- --- 4/3* 4/3* ---

450-1500 --- --- 4/3* 4/3* 4/3* --- ---

< 450 --- --- 4/3* 4/3* --- --- ---

NH/SHs(Hills)

> 1500 --- --- --- --- 4/3*+ 4/3* 4/3*+

450-1500 --- --- --- 4/3+ 4/3*+ 4/3*+ ---

< 450 --- --- 5/4* 5/4*+ --- --- ---

(II) Life Cycle (in years) for MDR/ODR/VR

Type of Treatment/ Category of Road

Traffic Intensity in CVD

MR-I **SD-ISD-II

PC + SC 20 mm MSS 25 mm SDBC

25 mm BC

MDR/ODR/VR (Normal)

> 1500 --- --- --- --- 5/4* 5/4*

450-1500 --- --- --- 5/4* 5/4* ---

150-450 --- --- --- 5/4* 5/4* ---

< 150 5/4* 5/4* 5/4* --- --- ---

MDR/ODR/VR (Urban)

> 1500 --- --- --- --- 4/3* 4/3*

450-1500 --- --- --- 4/3* 4/3* ---

150-450 --- 3 4/3* 4/3* --- ---

< 150 3 4/3* 5/4* 5/4* --- ---

MDR/ODR/VR (Hills)

> 1500 --- --- --- --- 4/3*+ 4/3*+

450-1500 --- --- --- --- 5/4*+ 5/4*+

150-450 --- 3 5/4* 5/4*+ --- ---

< 150 4/3* 4/3* 5/4* --- --- ---

Note: ````` A.* Indicates reduced life of treatment due to high rainfall i.e. > 3000 mm.B. + Indicates reduced life due to higher altitude i.e. > 2000 Mts.C. ** This treatment of SD-I is to be used under condition of severe resource crunch only.D. The treatment symbols have been explained in para 29.6.4.

Assessment of pavement distress and required maintenance measures

Various types of pavement distress ranging from minor and localized failures to major and

general failures may take place on road pavements. The failures may be due to one or a

combination of several causes. Road maintenance forms an important component of the entire

road system.

The maintenance operations involve (i) assessment of road condition periodically (ii)

diagnosis of the problem (iii) finding the causative factors and (iv) adopting the most

appropriate maintenance steps with least possible delay.

Once any particular type of pavement distresses develops particularly in a flexible pavement,

the rate of growth of deterioration is exponential. Therefore, the proverb, ‘a stitch

in time saves nine’ is very apt with respect to road

maintenance woks.