Pavement maintenance, nac

PAVEMENT MAINTENANCE

A.Ramesh, M.Tech, MITE, (Ph.D)

Sr.Asst.Prof, CED,VNR VJIET

8/2/2011 Construction Project Management,

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Warning Bells by World Bank on the Need for

Pavement Maintenance in Developing Countries

• Failure to maintain roads is tantamount to an act of disinvestment; it implies sacrifice of past investments

• A dollar saved in road maintenance can increase the VOC by 2 to 3 dollars

• Transportation crisis is looming large in several developing countries where the escalating damage to the roads is not contained.

• Without corrective action many developing countries may soon face a situation in which poor roads, and therefore inadequate road transport, become an insurmountable obstacle to economic recovery and growth.


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What is Pavement Maintenance?

• Pavement maintenance is treatment of road defects

The first step in the maintenance process is collection of information about defects

• Some defects are environment-related, like silting of drains, clogging of culverts & vegetation growth. These are treated under routine maintenance (say, twice a year).

• Traffic induced defects are assessed by manual and mechanical methods and treated according to the type and intensity of defect.


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Pavement Defects

• In asphalt surface

– Cracking

– Ravelling

– Rutting

– bleeding

– Potholes

– Edge deterioration

• Shoulder

– Deformation & scour

– Vegetation growth

• Side drains

– Silted or blocked

– Scoured or damaged

• Culverts

– Silted or blocked

– Scoured or damaged

– Damaged guard rails


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Defects Measurement

• Measuring wheel is run to give chainage and length of

defect.

• Width of defect measured with tape at start and finish of

defect

– Ignore small areas, < (1m x 0.5m), of cracking &

ravelling (loss of stone)

– Record all potholes with size 0.3m x 0.3m and above

– Ignore edge deterioration of length < 1 metre

• An example of defects measurement of asphalt surfaced

pavement is shown in next two slides


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Defective sectionRight

shoulder

10095

Not to scale

20

Cracking

Edge deterioration

Ravelling

Figure: Example of a defective sub-section

200

180

120

90

0

Edge deterioration

80

30

Ch

ain

age

Left

shoulderCarriageway


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Defects Measurement

Left Right

Length

(m)

Width

(m)

Length

(m)

Width

(m)

Length

(m)

Width

(m)

Length

(m)

Width

(m)

Length

(m)

Width

(m)

Chainage

(m)

Chainage

(m)

Chainage

(m)

Depth

(mm)

30 0.5

120

90

95 4 80 2 110

95

0

180

100

200

90

30 0.5 60 0.5 30

30

0

80

20

30

0

Pot-holes Rut depthEdge deterioration

Figure: Example of a completed visual inspection form for asphalt- surfaced pavements

Asphalt- surfaced pavement condition survey

Name of the Road Date

Section

Length Width

Link No.

Cracking Ravelling


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Explanation of Defects Measurement

Procedure

• The form is divided vertically into pairs of rows. It is filled in bottom up.

• The lower left col. of each pair of rows records start & end chainages of particular defect.

• The top right col. of each pair records the width of that defective area

• The top left col. of each pair records the difference in chainages (length of defective area).

• The entries into the form progresses gradually up the page as the survey moves along the road.

• Rut depth is recorded at 100 m interval in both wheelpaths. The greater of the values recorded with its chainage.

• Make a note of bleeding and shoving separately


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Defects of Off-road Features

• Defects of shoulders, side drains, guard rails, all

involve measurement of defective length.

– An example is given in the next slide


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Defects Measurement

−−−−70−−−−210

140

−−−−−−−−−−−−−−−− −−−− −−−−70 125 15 210 15 15

−−−−−−−−−−−−−−−− −−−− −−−−50 125 140 210 90 90

20 0 125 0 75 75

−− −− −− −−

Shoulder width 2.0 metres

Culverts2

Gu

ard

rail

Ret

ain

ing

wall

Side drain

Right

Off-road Features condition survey

Name of the Road

Section

Date

Link No.

silt

ed

scou

r

Left

Shoulder width 2.0 metres

Ret

ain

ing

wall

footway

shoulder

gra

ss

scou

r ker

b

Gu

ard

rail

ker

bshoulder

silt

ed

scou

r

gra

ss

scou

r

Side drainfootway

−−−−−−−− 50 195 15 −−−−−−−− 15 −−−− 15210 −−−−−−−−Silted/blocked

Scour/damage

Example of a completed visual inspection form for off-road features

−−−−


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Detailing of Pavement defects

• Defect: Cracking

• Location:

– Longitudinal, in wheel tracks

& edges

– Transverse, across cross

section

– Mesh cracking

• Main causes

– Poor quality materials

– Poor workmanship

– Less pavement thickness

– Aged pavement


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Detailing of Pavement Defects

• Defect: Cracking (continued)

– Development

If neglected, general or local destruction of pavement

– Remedies

• Surface cracking: local sealing or filling of cracks

• Cracks in pavement structure: local sealing, filling

of cracks and patching when cracking is severe

(see maintenance treatments)


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Treatment of Defects

• Treatment: Local Sealing

• Defects treated: Cracks & Final treatment for local repairs

• Material used

– Cutback bitumen, coarse sand up to 5 mm, chippings 6 to 10 mm size for local repairs

• Execution steps

– a) sweep area (surface must be clean & dry)

– b) mark out the area to be sealed, with chalk


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Treatment of Defects

• Local Sealing (continued)

– c) distribute binder (use

water can) 1kg/m2 ; do not

overheat bitumen.

– d) distribute aggregate by

scattering with shovel..

Whole area must be covered.


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Execution of Works

crack sealing

• Defects treated

– Closely spaced cracks

• Materials used

– Bituminous slurry

• Execution

– a) Sweep the area (surface

must be dry and clean)

– b) mark out the area to be

repaired, with a chalk


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Execution of Works

crack sealing

– c) prepare bitumen slurry

by mixing 6 litres of

bitumen emulsion with20

litres of coarse sand (<

5mm)

– d) Spread the slurry with

squeegee in thin layer 5

mm thick) over marked

area.Allow it to dry before

allowing traffic


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Execution of Works

crack sealing (continued)

• Defect treated

– Isolated cracks

• Materials used

– Cutback bitumen, coarse sand

• Execution

– a) Sweep the area clean and dry

– b) Heat the binder (cutback). Do not overheat; use thermometer.Distribute the binder with water can to follow the line of crack. Hold the nozzle close to the road

– c) Scatter coarse sand over strip of binder using shovel.


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Detailing of Pavement Defects

(continued)

• Defect: Ruts and Depressions

– Location

• In wheel tracks of vehicles (ruts)

• Local areas (depressions)

– Main causes

• Insufficient subgrade or pavement strength

• Inadequate stability of bituminous mix


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Detailing of Pavement Defects(continued)

• Ruts and Depressions (continued)

– Development

If neglected water penetrates, rapid increase in rutting;

leads to cracking and breaking up of pavement

– Remedies

• Slight rutting (< 50 mm): filling in of ruts and

depressions

• Deep rutting: local restoration of pavement structure


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Execution of WorksFilling in Depressions

• Defects treated

– Pavement subsidence and surface irregularities

• Materials used

– Cold mix asphalt, prepared in advance and stored

• Execution

– a) sweep depressions. (Surface to be clean and dry)

– b)Mark out the area with chalk. Remove high spots with pick axe

– c) Obtain cold mix


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Execution of Works

Filling in Depressions– d) Application of tack

coat.Spray hot cutback with water can at nearly 0.5kg/m2. Do not overheat cutback.

– e) Fill in depression. Place cold mix within marked outline. Use a rake. Leave excess thickness about one third of depth of depression to allow for compaction.

– f) Compact material. Compact thoroughly using small vibratory roller or a rammer until level is 3 mm proud of surrounding area

– g) Resealing. Seal (local sealing) the repair to prevent penetration of water.


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Execution of works

Base Patching

• Defects treated

– Mesh cracking, ruts and

depressions, edge

subsidence and rutting,

potholes, shoving

• Materials used

– Selected well graded

granular material, cold mix

asphalt

• Execution

– a) Mark out the area with

chalk (draw a rectangle

around defect)

– b) Excavation of area:

Remove all material of

road surface from the

marked out area.


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Execution of works

Base Patching

– c) Increase depth of hole

until firm dry material is

found. Trim the walls of

the hole to be vertical.

Remove all moisture

d) Trim bottom of hole so

that it is flat horizontal

and free of loose

material and compact


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Execution of works

Base Patching

• Backfilling Hole

– Fill hole with selected well graded material. Material may be of same quality as base layer that is repaired or cold asphalt mix

– Place material in the hole and compact in one or more layers. The last layer to have greater thickness (1/5th extra) to allow for settlement after compaction

– For compaction, use vibratory roller, plate compactor or rammerdepending on size of excavation

• Resealing

– Reseal (local sealing) to prevent penetration of water


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• Defect: Bleeding

– Location

• May involve part or whole of road surface

– Main causes

• Too much binder

• Unsuitable binder

– Development

If neglected

• Road surface slippery when wet

• Separation and break-away of surface layer under traffic

– Remedies

• Sanding

• Surface dressing


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Sanding

• Defect treated:Bleeding

• Material used : coarse

sand up to 5 mm size

• Execution

– a) Scatter sand with

shovel from truck or trailer

– b) Spread sand with

broom; cover surface

evenly


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• Defect: Edge subsidence and Rutting

– Location

• Along edge of pavement bordering unsealed

shoulders

– Main causes

• Badly maintained shoulders

• Penetration of water and loss of bearing strength

• Poor drainage


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• Edge subsidence and Rutting (continued)

– Development

if neglected, subsidence increases rapidly leading to disintegration of edges

– Remedies

• Slight subsidence (< 50 mm): filling of ruts and depressions; restoration of shoulder

• Deep subsidence: local restoration of pavement structure and shoulder

• Improvements to drainage

(see maintenance treatments)


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• Defect: Potholes– Location

• No particular location, often in cracked areas, deformation or aggregate loss

– Main causes

• Poor quality of pavement material

• Infiltration of water

• Break away of material under action of traffic

– Development

If neglected progressive enlargement of pothole and formation ofadditional potholes

– Remedies

• Local restoration of pavement structure


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Common Types of Pavement Defects: Potholes


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Common Types of Pavement Defects: Shoving


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Common Types of Pavement Defects: Surface

Shoving or Creep


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Common Types of Pavement Defects: Edge Damage


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Common Types of Pavement Defects: Ravelling


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Common Types of Pavement Defects: Fatting up or

Bleeding


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Common Types of Pavement Defects: Edge Step


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Common Types of Pavement Defects: Pavement Slip


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Common Types of Pavement Defects: Transverse

Cracks


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Common Types of Pavement Defects: Block Cracks


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Common Types of Pavement Defects: Cracking in

Wheeltracks


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Common Types of Pavement Defects: Crocodile

Cracking


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Common Types of Pavement Defects: Wheeltrack

Rutting (I)


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Rutting (II)


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Rutting & Cracking


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TRL Dynamic Cone Penetrometer

Handle

Falling Hammer (8kg)

Top rod (Hammer shaft)

Coupling

Handguard

Clamp ring

Bottom rod

1 meter rule

600 cone

dia 20 mm

600 inc

Fig. TRL Dynamic Cone Penetrometer


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DCP Test ResultLog10(CBR) = 2.48 – 1.057Log10(pen. rate)


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Sources of Presentation Material

• PIARC Road Maintenance Hand Book

• TRL Overseas Road Note 31

• Road Deterioration in Developing Countries – World Bank Policy Study


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Pavement Maintenance

END OF TALK

Pavement maintenance, nac

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