Keeping Up Appearances-Municipal Road Maintenance

7/27/2019 Keeping Up Appearances-Municipal Road Maintenance

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A Stitch in Time

Asphalt pavements are remarkably resilient and with proper

maintenance should last for at least 20 years. The key is

proper maintenance. As the garage owner on a commercial

for oil filters so eloquently put it: You can pay me now or you

can pay me later. Spending a dollar on preventive mainte-

nance in the tenth year of a pavements life can save up to five

dollars in corrective maintenance five years later.

Preventive maintenance is an organized, systematic

approach to maintain and improve the condition of a road and

slow future deterioration. By correcting small problems before

they become big ones, you eliminate the worst first syndrome(and the irate calls from motorists who have just had to have

a new alignment job), save money by postponing major reha-

bilitation projects, reduce traffic delays and improve the per-

formance of the entire road network.

An effective preventive maintenance program has three

components: identifying the most appropriate candidates for

maintenance, doing the maintenance before problems get out

of hand, and selecting the right maintenance technique.

An up-to-date pavement condition survey identifies the

type of pavement distresses in the road network, evaluates

those distresses based on severity and extent, and establishes

which roads need to be fixed first. A condition survey

shouldnt just tell you which pavements have problems that

need correcting today. It should also tell you which pavements

need treatment today to avoid problems tomorrow.

Knowing that a pavement needs maintenance is one

thing. Carrying out the treatment on time and on schedule is

another. You need to apply preventive maintenance treatments

before the problem gets out of hand, not after. It makes sense

for example, to rout and seal before a single crack spreads into

multiple cracks. When budgets are tight, preventive mainte-

nance is often one of the first items to be sacrificed. It isshort-term gain for long term pain. Dedicated funding needs

to be part of any preventive maintenance program.

Finally, you need to select the right treatment. There are a

number of preventive maintenance techniques, each of which

has been specifically developed to treat specific types of

distress at specific levels of severity. The decision as to which

treatment to use typically depends on the type of pavement

the type, extent and severity of the pavement distress, and the

type of road (its use, volume, and traffic speed).

You didnt see it coming but theres no mistaking that dull thud. Youve hit a pothole and its going to be expensive. Anew tire can cost up to $400. A wheel alignment costs about $200. Replacing the tire rims: as much as $800. Nowonder motorists vent their frustrations in the annual poll of the worst roads in the province. But if a municipality isscrambling to fill potholes and repair crumbling roads, its probably too little, too late and too expensive.

We asked three Ontario municipalities about their road maintenance and rehabilitation programs - a major urbancentre, a large county, and a small municipality.

But first, a maintenance and rehabilitation primer.

Municipal Road Maintenance and RehabilitationMunicipal Road Maintenance and Rehabilitation


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restores the pavements profile and cross-fall. Once the new

base is finished, the contractor completes the job with a new

layer of asphalt.

The entire construction process typically takes two to

three days after which the lane can be immediately opened for

traffic.

The County of Middlesex

Each year, we review every kilometre of the roads in our

network, says Chris Traini, the county engineer for Middlesex

County. It is something I like to do myself. First of all

because the road condition survey is subjective, having the

same person do it every year ensures consistency and secondit gives me the opportunity to see the condition of the roads

for myself. You get a much better appreciation of whats going

by getting out in the field than you do by reading a consul-

tants report.

Chris bases his assessment on OGRAs pavement condition

guidelines for the type of distress, the severity of the distress

and the ride quality and assigns a pavement condition index

rating to each road in the asset management model.

We have been using the pavement performance system

for almost a decade and we have council buy-in and support

to make sure that we are doing the right work, he says.

One of the things that we look at is the percent of the

system that is rated as adequate and we have seen some steady

improvement. Five years ago, 44 percent of our network was

rated adequate. Last year, it was 53 percent, which means tha

half the network should last at least another 10 years withou

major rehabilitation.

The county does maintenance and rehabilitation on abou

84 lane-kilometres a year, which means that the entire network

will be rehabilitated over an 18 year period - consistent with

Selecting the right treatment should also be as much an

economic decision as a technical one based on how long a

particular treatment can extend the life of the pavement and

thus postpone or eliminate expensive rehabilitation projects.

On the Road to Rehab

A typical asphalt pavement should last between fifteen and

twenty years. With a bit of luck (and a good preventative

maintenance program, a road can last as much as 30 years.

But eventually all roads require major rehabilitation as theyget close to the end of their useful life.

Most signs of distress such as cracks, small potholes, and

stripping can be fixed with normal maintenance techniques.

Even severe defects can be repaired relatively quickly and

easily as long as they are localized. In fact, a well-planned,

well-executed preventive maintenance program can extend

the life of roads by up to fifteen years. But when the pavement

starts to show extensive structural defects, it is time for a

complete rehabilitation.

All rehabilitation projects should start with an engineer-

ing inspection. Engineers will examine the road, take some

core samples, use ground penetrating radar to check subsurfaceconditions, carry out deflection tests and review the condition

and performance of the existing road to ensure that any

underlying problems are corrected before the new pavement is

laid. Drainage problems, for example, need to be corrected, the

road profile will need to be restored, and measures put in place

to avoid reflective cracking (the propagation of existing cracks

in a pavement into a new overlay)

The most popular method of rehabilitating roads is the use

of a hot mix overlay - a new layer of hot mix pavement laid

over a reconstructed base. Done properly, an overlay should

give between 15 and 20 years of extended pavement life -

almost as good as a brand new pavement at considerably lessexpense.

The contractor starts the process by preparing the old

pavement. In most cases if the pavement structure is still

sound, a shave and pave is all that is needed. The contractor

mills the top layer of asphalt (which can then be recycled) and

then lays the new layer of asphalt.

Pavements with severe structural problems will need

additional rehabilitation techniques. Cold In Place Recycling is

a construction technique that turns part of the existing

pavement into a new aggregate base. About three-quarters of

the existing pavement is removed (typically between 65 and

125 mm.), mixed with an emulsion or expanded asphalt,re-laid and then compacted. After a short period to allow the

stabilized mixture to cure, the contractor lays down one or

two lifts of asphalt to create a new pavement. The entire

process is carried out in-situ. None of the old pavement is

removed from the site.

Full Depth Reclamation takes the process one step further

by processing the entire flexible pavement and a predeter-

mined portion of the base material. By completely removing

the old pavement, full depth reclamation erases all deep cracks

thus eliminating any possibility of reflective cracking. It alsocontinued ..

County of MiddlesexRoad Maintenance and Rehabilitation

Population: 71,200

Area: 1,776 square kilometres

Roads:

1,583 lane kilometres

100% paved

90% rural / 10% urban

Action Areas:

Corporate Culture of Sustainability

Healthy Communities

Economic Vitality Sustainable Natural Environment

Education, Engagement and Partnerships

Sustainability Implementation and Monitoring

Road Budget (2009):

Capital - $8.9 million

Rehabilitation - $6.2 million

Kilometres to be rehabilitated - 64


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Keeping Up Appearancescontinued from page 11

the life span of most asphalt roads. This year, the county is

planning to do 64 kilometres of road rehabilitation, somewhat

less than normal due to an unusually large expenditure

scheduled for a major bridge rehabilitation project.

The county uses surface treatment and microsurfacing,

which typically extends the life of a road from two to fiveyears, for low volume lightly travelled roads. It also uses

surface treatment in urban areas as a stopgap measure on

roads scheduled for major utility work in the near future.

The countys preferred choice for road rehabilitation is

cold-in-place recycling with a hot mix overlay - a technique

that converts the old pavement into a new roadbed.

We have done about 400 lane-kilometres of CIP over the

last 13 years, says Traini. It eliminates transverse and edge

cracking and the quality of the surface holds up really well.

The county expects to do about 24 lane-kilometres of CIP

this year. Another 6 lane-kilometres will be completely recon-

structed.

But when it comes to maintaining the roads and

preventing future distress, it is not always the most obvious

solution that has the biggest payoff.

Last year under a separate contract, the county added

about 12 kilometres of subdrains to the network. A lack of

good drainage is probably the biggest cause of pavement

failure, Traini points out. We are a big proponent of good

drainage and we put in subdrains where we can, which helps

eliminate settlement and alligator cracking.

A little bit of paint helps too.

We like to paint the edges of all our roads, concludesChris. It keeps the traffic to the center of the road and helps

keep the stress off the edges. Why spend the money fixing a

problem, if you can eliminate the problem in the first place?

The City of Ottawa

Keeping track of 5,000 kilometres of roads is almost a full time

job, says John Morand, project manager for the City o

Ottawas Infrastructure Services Branch, which is why the city

relies on its Pavement Management Application software

package. The PMA is used to maintain an inventory of all city

roads, tracking daily traffic volume, riding comfort, surface

distress, structural adequacy of the pavement structure andsoils, past maintenance history and other road inventory data

Ottawa went through a large amalgamation process in 2001

and considerable effort has been spent on validating the

inventory data.

Each year, the city updates the pavement condition infor-

mation on about 20 percent of the road network using trucks

mounted with sensors and cameras to collect data on riding

comfort and surface distresses. The field information is then

fed into the software, which uses the pavement condition data

to calculate a Pavement Quality Index.

About 20 percent of the road network is considered to be

in need but with current funding levels, we can only resurfaceabout 2 to 3 percent of the paved road network each year,

says Morand. We are starting to fall behind.

In order to make the most effective use of the funds that

are available (and to avoid subjective assessments by staff and

council), the city staff ranks each road section based on

technical priorities using factors such as traffic volume

improved Pavement Quality indicator, and need year. Roads

with higher traffic volumes and roads that have been in a

backlog condition for a number of years get higher scores

Arterial and collector roads, particularly those that carry sub-

stantial bus and truck traffic, are rehabilitated more frequently

than local roads.The staff then conducts a visual inspection of the highest

priority roads to ensure the validity of the ratings and prepares

a resurfacing list for the next capital budget.

Periodic resurfacing and rehabilitation is much more cost

effective in the long run than reconstruction, which can be a

costly and disruptive exercise, says Morand. By sealing the

road surface and correcting minor road imperfections, a pres-

ervation treatment extend the life of a pavement at signifi-

cantly lower cost than conventional mill and overlay

treatments, in-place recycling or reconstruction.

About one-third of Ottawas 2009 budget has been

allocated to preservation-type treatments such as microsurfac-ing, thin lift overlays, slurry seals, crack sealing and surface

treatments and will be used on roads that are not as yet tech-

nically identified as needs in the Pavement Management

system.

Morand is particularly enthusiastic about microsurfacing

We can get five to seven years more life out of a road

after microsurfacing and it improves rideability as well, he

says. A lot of our roads are heavily pitted and polished but

once they have been microsurfaced the skid resistance comes

City of OttawaRoad Maintenance and Rehabilitation

Population: 1,150,000


Roads:

Center line kilometres - 5,500 40% rural / 60% urban

50 % built before 1980

Action Areas:

Corporate Culture of Sustainability

Healthy Communities

Economic Vitality

Sustainable Natural Environment

Education, Engagement and Partnerships

Sustainability Implementation and Monitoring

Road Budget (2009):

$14.6 million for resurfacing $6.5 million for preservation


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City of BrockvilleRoad Maintenance and Rehabilitation

Population: 24,000


Roads:

120 center-lane kilometres

273 lane-kilometres

Road Budget (2009):

$350,000 (milling overlaying and crack sealing)

(plus an additional one-time expenditure of $130,000 from gas tax funding)

right back to where it should be. And at about $4 a square

metre, its almost half the cost of a thin lift overlay.

The city expects to be able to use pavement preservation

techniques on about 70 kilometres of roads this year. An

additional 30 kilometres of roads will be completely resurfaced,

typically using shave and pave and partial and full depthin-place recycling techniques.

The city also hopes to use more warm mix next year (a

new asphalt that is laid at cooler temperatures than tradi-

tional hot mix and thus conserves energy and reduces

greenhouse gas emissions).

We did a 3,500 tonne warm mix trial to pave about seven

kilometres on John Quinn Road last year and its holding up

well, Morand concludes.

City of Brockville

Smaller municipalities dont need a complicated or sophisti-cated pavement management program, maintains Conal

Cosgrove, director of operations for the city of Brockville.

With just over a hundred kilometres of roads, it is a

relatively small inventory. Handling the assessment is a very

manageable job for one person to do and because the appraisal

is somewhat subjective, having the same person do it every

year provides some consistency.

Each road is given a pavement condition index based on

a visual rating and the ratings are updated annually.

Reconstruction work is based on a three-year forward looking

assessment and integrated with the 10-year capital budget.

The reconstruction plan is also co-ordinated with a utilitiesco-ordinating committee to make sure, as Conal says, that we

are not working at cross-purposes.

Council sets the budget and then we try to maintain a

balance between reasonable size paving jobs and making sure

that we are covering as much of the city as we can, he says.

But at the rate that we are reconstructing our roads, it is

going to take about 50 years to do the entire network and

asphalt pavement just doesnt last that long. Even though our

budget is increasing, we are falling behind.

Last year, the city rehabilitated just under three kilometres

of roads - less than 3 percent of the road network.

Over 90 percent of our roads are urban cross-section and

our biggest issue is reflective cracking so surface treatment is

not usually effective, Cosgrove points out. If we are going to

do the work, we prefer to do a mill and overlay to get rid ofshallow cracking and re-establish a good drainage profile.

The Brockville staff periodically reviews the latest

pavement technology and mixes to see if any of them are

applicable but given the volume of traffic in the city, Cosgrove

says that the tried and true works fine.

We are not going to use something just because it is new

A smaller municipality has the advantage of keeping i

simple.

continued with Glossary ofPavementMaintenanceTechniques..


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Hot Mix Overlay: placing a layer of hot mix over existingpavement. Thin overlays are at least 40mm thick if conventionalasphalt is used but thinner overlays can be laid with specializedmixes. The most common rehabilitation technique (as opposed topreventive maintenance technique) is a similar form of hot mixoverlay. Commonly known as Shave and Pave, this processinvolves the contractor milling and replacing up to 80mm ofasphalt. Thicker overlays can extend the life of a pavement bybetween 15 and 20 years.

Benefits: provides new waterproof surface mitigates surface ravelling

seals small cracks improves ride quality and corrects surface irregularities improves surface friction

Selection and Application: used on stable pavements with asound base, but have a surface which exhibits minor surfacedistresses such as cracking, rutting, ravelling and roughness.Can be used to strengthen pavements. Do not use onpavements showing structural distress or pavement failure.Defects will quickly reflect through the new surface.

Service Life: 5 to 15 years

Hot in Place Recycling: heating the existing pavement andreblending the asphalt. Rejuvenators and virgin hot mix may beadded. Typical thickness: 25 - 50 mm.

Benefits: provides new waterproof surface slows surface ravelling seals small cracks improves ride quality and corrects surface irregularities improves surface friction

Selection and Application: used on stable pavements with asound base, when the surface exhibits minor surface distressessuch as cracking, rutting, ravelling and roughness. Can be used

to strengthen the pavement when applied in conjunction withan HMA overlay. Do not use on pavements showing structuraldistress or pavement failure. Defects will quickly reflectthrough the new surface.

Service Life: 5 to 12 years

GLOSSARY OFPAVEMENT MAINTENANC

Micro-surfacing: the application of a cold mix of dense-gradedaggregate, polymer modified asphalt emulsion, water, and minerafillers. Capable of filling wheel ruts up to 40mm deep when thepavement has stabilized and is not subject to plastic deformation.

Benefits: improves surface friction slows surface ravelling, seals small cracks improves ride quality and corrects surface irregularities

Selection and Application: used on stable pavements with asound base that have minor surface distresses such ascracking, rutting, ravelling and roughness. Can be used tocorrect rutting. Do not use on pavements showing structura

distress or pavement failure. Defects will quickly reflectthrough new surface

Service Life: 5-7 years

Fog Seal: a light application of diluted slow-setting emulsion.

Benefits: rejuvenates dry and brittle asphalt surfaces seals very small cracks and surface voids slows the rate of weathering and oxidation

Selection and Application: Use on structurally sound

pavements to improve surface conditions on pavementsshowing signs of minor cracking, weathering, segregation oravelling.

Service Life: 1 - 2 years

Crack Sealing: routing, cleaning and filling the crack with sealantMoisture infiltration is the primary cause of pavement deteriora-tion Crack sealing prevents water and debris from entering a crackCrack Filling does not involve routing and does not fully seal thecrack.

Benefits:

prevents moisture and debris from getting into cracks prevents water damage to the pavements structure extends pavement life by 3-5 years

Selection and Application: use for cracks less than 25mmwide, spaced uniformly along the pavement and with limitededge deterioration. Use Crack Filling for older pavements withwider, more random cracking. Best applied during cool dryweather (0C - 15C) when cracks are almost fully open.

Service Life: 3- 5 years


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TECHNIQUES*

Cold Planing or Milling: removes bumps, ruts and irregularities,restores the profile and leaves a uniform, textured surface.

Benefits: improves ride quality and corrects surface irregularities .improves surface friction

Selection and Application: cold plane before applying a rec-ommended resurfacing product. A tack coat should be appliedto all milled surfaces prior to paving the new riding coarse

Service Life: Typically resurfaced within 48 hours; whenoverlaid with HMA, service life is similar to milland overlay treatment

Cold In-Place: reprocesses existing pavements in-situ to a depthof 100 mm. Typically overlaid with 1 or 2 lifts of HMA to producea sound pavement structure.

Benefits: uses 100% existing aggregates and asphalt mitigates reflective cracking corrects cross fall and longitudinal grades of existing

pavements

Selection and Application: use on stable pavements with asound base showing surface distresses such as cracking,

rutting, ravelling and roughness.

Service Life: 10- 12 years

Chip Seals: a uniform application of asphalt emulsion to a preparedpavement surface followed by a rolled aggregate cover (OPSS 304Class 1-6 Surface Treatments). Can postpone the need for heaviersurface treatments or resurfacing for 2 to 4 years.

Benefits: improves surface friction slows surface ravelling and oxidation, corrects minor deformations and seals small cracks

provide temporary cover for a base course until the finalasphalt courses can be placed

Selection and Application: provides an economical all-weather surface for light to medium traffic (polymer-modifiedemulsions and high quality aggregates should be for highertraffic volume applications). Must be applied to structurallysound pavements.

Service Life: 5 to 7 years for chip seals and 2 to 4 years forsand seals

Slurry Seal: a cold mix paving technique using a mixture of dense-graded aggregate, asphalt emulsion, water, and mineral fillers.


Selection and Application: use on stable pavements with asound base showing minor surface distresses such as crackingrutting, ravelling and roughness. Do not use on pavementswith structural distress, as cracks will quickly reflect throughnew surface. Minimum thickness is 9.5mm

Service Life: 5 years plus

Cape Seal: a chip seal followed by a slurry seal.


Selection and Application: use on stable pavements with asound base showing minor surface distresses such as crackingrutting, ravelling and roughness. Do not use on pavementswith structural distress, as cracks will quickly reflect through

new surface.

Service Life: 5 -7 years

*Adapted from the Ontario Hot Mix Producers Associations publication The ABCs of Pavement Preservation. The entire ABC asphalpaving series is available at www.ohmpa.org

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