1. ROAD FAILURES AND THEIR MAINTENAINCE
ABSTRACT
Roads are mostly used than other modes of transportation. The passengers and goods are
first transported by roads to railway station or airports so it acts as feeder system to other modes
of transportation.. Inadequate transportation facilities or bad condition of roads retard process of
socio economic development of country so Roads should have good condition for smooth riding.
Road maintenance is one of the most important components for entire road system. The
badly maintained road leads to a large number of accidents as result of which loss of lives every
year and greater consumption of fuel. Maintenance operations involve assessment of road
condition, diagnosis of the problem and adopting most appropriate steps for maintenance. Even
if highway are well designed and constructed but after a course of time they require maintenance
extent of which depend upon types of pavement and various types of failures in pavement
ranging from minor to major and general failure. So as to ensure smooth transportation these
failures are minimize using maintenance approaches.
Keywords: - Road
Failures, Road Maintenance, Pavement, transportation.
2. INTRODUTION
CHAPTER-1
1.0Introduction
Road can be defined as a line of communication (travelled way) using a stabilized base
other than rails or air strips open to public traffic, primarily for road motor vehicles running on
their own wheels, which includes bridges, tunnels, supporting structures, junctions, crossings,
interchanges, and toll roads.. In urban areas roads may diverge through a city or village and be
named as streets, serving a dual function as urban space easement and route. The main purpose
of a pavement or roads to provide a satisfactory smooth surface upon which traffic can operate
smoothly or easily. The term pavement is defined as a structure consisting of one or more layer
of the processed materials.1
1.1 Road Pavements are constructed to achieve the following objects To distribute the concentrated loads so that the bearing capacity of the subgrade soil is
not exceed.
To provide adequate thickness of each of the layer.
To give a clean surface free from dust or particles.
To provide adequate support for the loads imposed due to traffic on pavement.
To provide smooth and safe all weather riding surface.
Road pavement are constructed to provide a firm and even surface for carriage way.
Pavement is prepared using broken stones, stabilized soil and binder materials to bind aggregates
to form a homonogenous pavement section but earth road may not be able to fulfill any of above
mentioned objective especially during varying condition of traffic load and weather at high
moisture content soil become weaker and soft and yield under heavy loads. The unevenness and
undulations of road surface along longitudinal profile of the road causes vertical oscillations in
fast moving automobiles, increasing the fuel consumption and wear of the vehicle component
increase in vehicle operation cost, uneven pavement surface causes discomfort and fatigue to the
passenger of fast moving vehicle so road pavement carries wheel loads and transfer the load
stresses through a wider area on sub grade. When road is not in good condition and not fulfilling
its object this can be due to the failure of road pavement.
3. 1.2 General causes of road failures Failure or deterioration of roads can be due to any one of the reason
Use of inferior quality materials in construction.
Sudden increase in traffic loading especially on new roads where the design is based on
lesser traffic is a major cause of cracking. After construction of good road, traffic of other
roads also shifts to that road. This accelerates the fatigue failure (Alligator Cracking).
Temperature variation ranging from 50º C to below zero conditions in the plain areas of
North and Central India leads to bleeding and cracking.
Provision of poor shoulders leads to edge failures.
Provision of poor clayey subgrade results in corrugation at the surface and increase in
unevenness.
Poor drainage conditions especially during rainy seasons, force the water to enter the
pavement from the sides as well as from the top surface. In case of open graded
bituminous layer, this phenomenon becomes more dangerous and the top layer gets
detached from the lower layers.
If the temperature of bitumen/bituminous mixes is not maintained properly, then it also
leads to pavement failure. Over heating of bitumen reduces the binding property of
bitumen. If the temperature of bituminous mix has been lowered down then the
compaction will not be proper leading to longitudinal corrugations.
So identify the failure and repair the particular and maintain good condition of road.
Badly maintained Pavement create problems so the maintenance of roads in necessary so as to
keep the road carriageway for smooth flow of traffic. Better road system provides Benefits to
the society as:
Reduction in vehicle operation cost per unit length of road.
Saving in travel time.
Reduction in accident rates.
Improved level of service and ease of driving.
Increased comfort to passengers.
So for socio-economic development of country it is necessary to have good condition of
roads and a system is adopted for better and efficient maintenance of roads is termed as
4. maintenance management system. The various factors included in maintenance management
system are Field surveys for evaluation of maintenance required.
Type and extent of maintenance required and various possible alternatives and their
Economic evaluation.
Maintenance cost, availability of materials, man power and equipments.2
5. LITERATURE REVIEW
CHAPTER-2
A road is a thoroughfare, route, or way on land between two places, which has been
paved or otherwise improved to allow travel by some conveyance, including a horse, cart, or
motor vehicle. Roads consist of one, or sometimes two, roadways each with one or more lanes
and also any associated sidewalks and road verges. Roads that are available for use by the public
may be referred to as public roads or highways. road construction requires the creation of a
continuous right-of-way, overcoming geographic obstacles and having grades low enough to
permit vehicle or foot travel. and may be required to meet standards set by law or official
guidelines The process is often begun with the removal of earth and rock by digging or blasting,
construction of embankments, bridges and tunnels, and removal of vegetation (this may
involve deforestation) and followed by the laying of pavement material. A variety of road
building equipment is employed in road building.
After design, approval, planning, legal and environmental considerations
have
been
addressed alignment of the road is set out by a surveyor. The radii and gradient are designed and
staked out to best suit the natural ground levels and minimize the amount of cut and fill.
Roads are designed and built for primary use by vehicular and pedestrian traffic. Storm
drainage and environmental considerations are a major concern. Erosion and sediment controls
are constructed to prevent detrimental effects. Drainage lines are laid with sealed joints in
the road easement with runoff coefficients and characteristics adequate for the land zoning and
storm water system. Drainage systems must be capable of carrying the ultimate design flow from
the upstream catchment with approval for the outfall from the appropriate authority to
a watercourse, creek, river or the sea for drainage discharge.[ 1]
According to a May 2009 report by the American Association of State Highway and
Transportation Officials (AASHTO) and TRIP a national transportation research organization—
driving on rough roads costs the average American motorist approximately $400 a year in extra
vehicle operating costs. Drivers living in urban areas with populations more than 250,000 are
paying upwards of $750 more annually because of accelerated vehicle deterioration, increased
maintenance, additional fuel consumption, and tire wear caused by poor road conditions.
6. Development of a country depends on the connectivity of various places with adequate
road network. Roads are the major channel of transportation for carrying goods and passengers.
They play a significant role in improving the socio-economic standards of a region. Roads
constitute the most important mode of communication in areas where railways have not
developed much and form the basic infra structure for the development and economic growth of
the country. The benefits from the investment in road sector are indirect, long-term and not
immediately visible. Roads are important assets for any nation. However, merely creating these
assets is not enough, it has to be planned carefully and a pavement which is not designed
properly deteriorates fast. India is a large country having huge resource of materials. If these
local materials are used properly, the cost of construction can be reduced. There are various type
of pavements which differ in their suitability in different environments. Each type of pavement
has it’s own merits and demerits. still in India, 98% roads are having flexible pavements. A lot of
research has been made on use of Waste materials but the role of these materials is still limited.
So there is need to take a holistic approach and mark the areas where these are most suitable.3
Pavements –That portion of a road designed for the support of, and to form the running
surface for, vehicular traffic. The portion of the road, excluding shoulders, placed above the
design sub grade level for the support of, and to form a running surface for vehicular traffic.
2.1 Types of road PavementsThere are two main types of road pavements; flexible pavements & rigid pavements
2.1.1 FLEXIBLE PAVEMENTFlexible pavements are so named because the total pavement structure deflects, or flexes,
under loading. A flexible pavement structure is typically composed of several layers of
material. Each layer receives the loads from the above layer, spreads them out, then passes on
these loads to the next layer below. Thus, the further down in the pavement structure a particular
layer is, the less load (in terms of force per area) it must carry.
In order to take maximum advantage of this property, material layers are usually arranged
in order of descending load bearing capacity with the highest load bearing capacity material (and
7. most expensive) on the top and the lowest load bearing capacity material (and least expensive)
on the bottom needed.
Fig. 1: - Typical section for a flexible pavement[4]
2.1.2 Basic Structural Elements
A typical flexible pavement structure consists of the surface course and the underlying
base and subbase courses. Each of these layers contributes to structural support and drainage.
The surface course (typically an HMA layer) is the stiffest (as measured by resilient modulus)
and contributes the most to pavement strength. The underlying layers are less stiff but are still
important to pavement strength as well as drainage and frost protection. A typical structural
design results in a series of layers that gradually decrease in material quality with depth.
Surface Course The surface course is the layer in contact with traffic loads and normally
contains the highest quality materials.
It provides characteristics such as friction,
smoothness, noise control, rut and shoving resistance and drainage. In addition, it serves to
prevent the entrance of excessive quantities of surface water into the underlying base,
subbase and subgrade (NAPA, 2001). This top structural layer of material is sometimes
subdivided into two layers (NAPA, 2001):
1. Wearing Course. This is the layer in direct contact with traffic loads. It is meant to
take the brunt of traffic wear and can be removed and replaced as it becomes worn. A
properly designed (and funded) preservation program should be able to identify
pavement surface distress while it is still confined to the wearing course. This way,
the wearing course can be rehabilitated before distress propagates into the underlying
intermediate/binder course.
8. 2. Intermediate/Binder Course. This layer provides the bulk of the HMA structure.
It's chief purpose is to distribute load.
Base Course The base course is immediately beneath the surface course. It provides
additional load distribution and contributes to drainage and frost resistance. Base courses
are usually constructed out of:
1. Aggregate. Base courses are most typically constructed from durable aggregates (see
Figure 2.5) that will not be damaged by moisture or frost action. Aggregates can be
either stabilized or unstabilized.
2. HMA. In certain situations where high base stiffness is desired, base courses can be
constructed using a variety of HMA mixes. In relation to surface course HMA mixes,
base course mixes usually contain larger maximum aggregate sizes, are more open
graded and are subject to more lenient specifications.
Sub base Course- The sub-base course is between the base course and the sub grade.
It functions primarily as structural support but it can also:
1. Minimize the intrusion of fines from the sub-grade into the pavement structure.
2. Improve drainage.
3. Minimize frost action damage.
4. Provide a working platform for construction.
The sub-base generally consists of lower quality materials than the base course but better than
the sub-grade soils. A sub-base course is not always needed or used. For example, a pavement
constructed over a high quality, stiff sub-grade may not need the additional features offered by a
sub-base course so it may be omitted from design. However, a pavement constructed over a low
quality soil such as swelling clay may require the additional load distribution characteristic that a
sub-base course can offer. In this scenario the sub-base course may consist of high quality fill
used to replace poor quality sub-grade (over excavation).5
9. Bitumen has been widely used in the construction of flexible pavements for a long time. This is
the most convenient and simple type of construction. The cost of construction of single lane
bituminous pavement varies from 20 to 30 lakhs per km in plain areas. In some applications,
however, the performance of conventional bitumen may not be considered satisfactory because
of the following reasons:
In summer season, due to high temperature, the bitumen becomes soft resulting in
bleeding, rutting and segregation finally leading to failure of pavement.
In winter season, due to low temperature, the bitumen becomes brittle resulting in
cracking, raveling and unevenness which makes the pavement unsuitable for use.
In rainy season, water enters the pavement resulting into pot holes and sometimes total
removal of bituminous layer.
In hilly areas, due to sub zero temperature, the freeze thaw and heave cycle takes place.
Due to freezing and melting of ice in bituminous voids, volume expansion and
contraction occur. This leads to pavements failure.
The cost of bitumen has been rising continuously. In near future, there will be scarcity of
bitumen and it will be impossible to procure bitumen at very high costs.
Recently, large number investigations have demonstrated that bitumen properties (eg.
viscoelsticity and temperature susceptibility) can be improved using an additive or a chemical
reaction modification.
2.1.3 Semi Rigid Pavements
The pavements constructed using the waste materials, which are more strong the
traditional aggregates may be treated as Semi-Rigid Pavement. A lot of research work has been
done in this direction. Visakhapatnam Steel Plant (VSP) at Visakhapatnam (AP) is one of the
major steel plants producing steel in the country. Granulated Blast Furnace Slag (GBFS) is also
generated as by-products of steel. Prior to 1991, a major portion of GBFS was being used by the
cement manufacturing industries located in the nearby areas but its utilization in this industry has
been decreasing gradually. This material has, therefore, been piling up gradually due to increased
production as a waste in the plant area a posing serious problem for its disposal. Two roads
namely Ankapalli-Pudimadaka Road (AP road) – a MDR and Bheemunipatnam-Narsipatnam
10. road (NB road) – a State Highway were selected for test track construction. The existing width of
the road pavement was about 3.5m and as per state PWD programme, has to be increased to
5.5m by 1m widening the carriageway on both sides of the road. The pavement thickness worked
out to be 425mm for the traffic parameter of 3 million standard axle (msa) for BN road and
480mm for the traffic parameter of 1.25 msa in case of AP road. The pavement compositions
were then, worked out considering the strength of GBFS, GBFS subgrade soil/moorum mixes for
the two roads. 3
2.1.4 Rigid Pavement
A rigid pavement structure is composed of a hydraulic cement concrete surface course
and underlying base and subbase courses (if used). Another term commonly used is Portland
cement concrete (PCC) pavement, although with today’s pozzolanic additives, cements may no
longer be technically classified as ―Portland.‖
The surface course (concrete slab) is the stiffest layer and provides the majority of strength.
The base or subbase layers are orders of magnitude less stiff than the PCC surface but still
make important contributions to pavement drainage and frost protection and provide a
working platform for construction equipment.
Fig.2 :- Typical section for a rigid pavement.6
11. Rigid pavements, though costly in initial investment, are cheap in long run because of low
maintenance costs. There are various merits in the use of Rigid pavements (Concrete pavements)
are summarized below:
Bitumen is derived from petroleum crude, which is in short supply globally and the price
of which has been rising steeply. India imports nearly 70% of the petroleum crude. The demand
for bitumen in the coming years is likely to grow steeply, far outstripping the availability. Hence
it will be in India's interest to explore alternative binders. Cement is available in sufficient
quantity in India, and its availability in the future is also assured. Thus cement concrete roads
should be the obvious choice in future road programmes.
1. Besides the easy available of cement, concrete roads have a long life and are practically
maintenance-free.
2. Another major advantage of concrete roads is the savings in fuel by commercial vehicles
to an extent of 14-20%. The fuel savings themselves can support a large programme of
concreting.
3. Cement concrete roads save a substantial quantity of stone aggregates and this factor
must be considered when a choice pavements is made,
4. Concrete roads can withstand extreme weather conditions – wide ranging temperatures,
heavy rainfall and water logging.
5. Though cement concrete roads may cost slightly more than a flexible pavement initially,
they are economical when whole-life-costing is considered.
6. Reduction in the cost of concrete pavements can be brought about by developing semiself-compacting.3
12. 2.2 FLEXIBLE PAVEMENT FAILURESFailures Of Flexible Pavements Can Be Of The Following Types
1. Fatigue (Alligator) Cracking-
Fig.3 : - Bad fatigue cracking
Fig.4 : - Fatigue cracking from frost action
Fig.5 : - Fatigue cracking from edge failure
Description: - Series of interconnected cracks caused by fatigue failure of the HMA surface
(or stabilized base) under repeated traffic loading. In thin pavements, cracking initiates at the
bottom of the HMA layer where the tensile stress is the highest then propagates to the surface as
one or more longitudinal cracks. This is commonly referred to as "bottom-up" or "classical"
fatigue cracking. In thick pavements, the cracks most likely initiate from the top in areas of high
localized tensile stresses resulting from tire-pavement interaction and asphalt binder aging (topdown cracking). After repeated loading, the longitudinal cracks connect forming many-sided
sharp-angled pieces that develop into a pattern resembling the back of an alligator or crocodile.
13. Problem: Indicator of structural failure, cracks allow moisture infiltration, roughness, may
further deteriorate to a pothole.
Possible Causes: Inadequate structural support, which can be caused by a myriad of things.
A few of the more common ones are listed here:
Decrease in pavement load supporting characteristics
o
Loss of base, subbase or subgrade support (e.g., poor drainage or spring thaw
resulting in a less stiff base).
o
Stripping on the bottom of the HMA layer (the stripped portion contributes little to
pavement strength so the effective HMA thickness decreases)Increase in loading
(e.g., more or heavier loads than anticipated in design)
Inadequate structural design
Poor construction (e.g., inadequate compaction)
Repair: A fatigue cracked pavement should be investigated to determine the root cause of
failure. Any investigation should involve digging a pit or coring the pavement to determine the
pavement's structural makeup as well as determining whether or not subsurface moisture is a
contributing factor. Once the characteristic alligator pattern is apparent, repair by crack sealing
is generally ineffective. Fatigue crack repair generally falls into one of two categories:
Small, localized fatigue cracking indicative of a loss of subgrade support. Remove
the cracked pavement area then dig out and replace the area of poor subgrade and
improve the drainage of that area if necessary. Patch over the repaired subgrade.
Large fatigue cracked areas indicative of general structural failure. Place an HMA overlay over
the entire pavement surface. This overlay must be strong enough structurally to carry the
anticipated loading because the underlying fatigue cracked pavement most likely contributes
little or no strength (Roberts et. al., 1996).
14. 2.Bleeding-
Fig.6 :- BST bleeding in wheelpaths
Fig.7 :- HMA bleeding from overasphalting.
Description: A film of asphalt binder on the pavement surface. It usually creates a shiny,
glass-like reflecting surface (as in the third photo) that can become quite sticky.
Problem: Loss of skid resistance when wet.
Possible Causes: Bleeding occurs when asphalt binder fills the aggregate voids during hot
weather and then expands onto the pavement surface. Since bleeding is not reversible during
15. cold weather, asphalt binder will accumulate on the pavement surface over time. This can be
caused by one or a combination of the following:
Excessive asphalt binder in the HMA (either due to mix design or manuacturing)
Excessive application of asphalt binder during BST application .
Low HMA air void content (e.g., not enough room for the asphalt to expand into during
hot weather)
Repair: The following repair measures may eliminate or reduce the asphalt binder film on the
pavement's surface but may not correct the underlying problem that caused the bleeding:
Minor bleeding can often be corrected by applying coarse sand to blot up the excess
asphalt binder.
Major bleeding can be corrected by cutting off excess asphalt with a motor grader or removing it
with a heater planer. If the resulting surface is excessively rough, resurfacing may be necessary
(APAI, no date given).
3.Block Cracking :-
Fig.8 :- Block Cracking
Description: Interconnected cracks that divide the pavement up into rectangular pieces.
Blocks range in size from approximately 0.1 m2 (1 ft2) to 9 m2 (100 ft2). Larger blocks are
generally classified as longitudinal and transverse cracking. Block cracking normally occurs
over a large portion of pavement area but sometimes will occur only in non-traffic areas.
16. Problem: Allows moisture infiltration, roughness
Possible Causes: HMA shrinkage and daily temperature cycling. Typically caused by an
inability of asphalt binder to expand and contract with temperature cycles because of:
Asphalt binder aging
Poor choice of asphalt binder in the mix design
Repair: Strategies depend upon the severity and extent of the block cracking:
Low severity cracks (< 1/2 inch wide). Crack seal to prevent (1) entry of moisture
into the subgrade through the cracks and (2) further raveling of the crack edges.
HMA can provide years of satisfactory service after developing small cracks if they
are kept sealed (Roberts et. al., 1996).
High severity cracks (> 1/2 inch wide and cracks with raveled edges). Remove and replace the
cracked pavement layer with anoverlay
4.Corrugation and Shoving
Fig.9 :- Corrugation and Shoving
Description: A form of plastic movement typified by ripples (corrugation) or an abrupt wave
(shoving) across the pavement surface. The distortion is perpendicular to the traffic direction.
17. Usually occurs at points where traffic starts and stops (corrugation) or areas where HMA abuts a
rigid object (shoving).
Problem: Roughness
Possible Causes: Usually caused by traffic action (starting and stopping) combined with:
An unstable (i.e. low stiffness) HMA layer (caused by mix contamination, poor mix
design, poor HMA manufacturing, or lack of aeration of liquid asphalt emulsions)
Excessive moisture in the subgrade
Repair: A heavily corrugated or shoved pavement should be investigated to determine the root
cause of failure. Repair strategies generally fall into one of two categories:
Small, localized areas of corrugation or shoving. Remove the distorted pavement
and patch.
Large corrugated or shoved areas indicative of general HMA failure. Remove the
damaged pavement and overlay.
5.Depression
Fig.10 :- Depression in left lane and shoulder
Description: Localized pavement surface areas with slightly lower elevations than the
surrounding pavement. Depressions are very noticeable after a rain when they fill with water.
18. Problem: Roughness, depressions filled with substantial water can cause vehicle hydroplaning
Possible Causes: Frost heave or subgrade settlement resulting from inadequate compaction
during construction.
Repair: By definition, depressions are small localized areas. A pavement depression should be
investigated to determine the root cause of failure (i.e., subgrade settlement or frost heave).
Depressions should be repaired by removing the affected pavement then digging out and
replacing the area of poor subgrade. Patch over the repaired subgrade.
6.Joint Reflection Cracking
Fig.11 :- Joint reflection cracking on an arterial
Description: Cracks in a flexible overlay of a rigid pavement. The cracks occur directly over
the underlying rigid pavement joints. Joint reflection cracking does not include reflection cracks
that occur away from an underlying joint or from any other type of base (e.g., cement or lime
stabilized).
Problem: Allows moisture infiltration, roughness
Possible Causes: Movement of the PCC slab beneath the HMA surface because of thermal
and moisture changes. Generally not load initiated, however loading can hasten deterioration.
Repair: Strategies depend upon the severity and extent of the cracking:
19. Low severity cracks (< 1/2 inch wide and infrequent cracks). Crack seal to prevent
(1) entry of moisture into the subgrade through the cracks and (2) further raveling of
the crack edges. In general, rigid pavement joints will eventually reflect through an
HMA overlay without proper surface preparation.
High severity cracks (> 1/2 inch wide and numerous cracks). Remove and replace the
cracked
pavement layer with an overlay.
2.3 Rigid Pavement Distress
Failures of rigid pavements can of following types
1.Blowup (Buckling)
Fig.12 :- Severe blowup
Description: A localized upward slab movement and shattering at a joint or crack. Usually
occurs in spring or summer and is the result of insufficient room for slab expansion during hot
weather.
Problem: Roughness, moisture infiltration, in extreme cases (as in the second photo) can pose
a safety hazard
20. Possible Causes: During cold periods (e.g., winter) PCC slabs contract leaving wider joint
openings. If these openings become filled with incompressible material (such as rocks or soil),
subsequent PCC slab expansion during hot periods (e.g., spring, summer) may cause high
compressive stresses. If these stresses are great enough, the slabs may buckle and shatter to
relieve the stresses. Blowup can be accelerated by:
Joint spalling (reduces slab contact area and provides incompressible material to fill
the joint/crack)
D cracking (weakens the slab near the joint/crack area)
Freeze-thaw damage (weakens the slab near the joint/crack area)
Repair: Full-depth patch
2.Corner Break
Fig.13 :- Corner break on a residential street
Fig.14 :- Corner break on a highway
Description: A crack that intersects the PCC slab joints near the corner. "Near the corner" is
typically defined as within about 2 m (6 ft) or so. A corner break extends through the entire slab
and is caused by high corner stresses.
Problem: Roughness, moisture infiltration, severe corner breaks will fault, spall and
disintegrate
21. Possible Causes: Severe corner stresses caused by load repetitions combined with a loss of
support, poor load transfer across the joint, curling stresses and warping stresses.
Repair: Full-depth patch.
3.Durability Cracking ("D" Cracking)
Fig.15 :- "D" cracking at panel corners
Description: Series of closely spaced, crescent-shaped cracks near a joint, corner or crack. It
is caused by freeze-thaw expansion of the large aggregate within the PCC slab. Durability
cracking is a general PCC distress and is not unique to pavement PCC.
Problem: Some roughness, leads to spalling and eventual slab disintegration
Possible Causes: Freeze-thaw susceptible aggregate.
Repair: "D" cracking is indicative of a general aggregate freeze-thaw problem. Although a fulldepth patch or partial-depth patch can repair the affected area, it does not address the root
problem and will not, or course, prevent "D" cracking elsewhere.
22. 4.Faulting
Fig.16 :- Faulting from ground level
Fig.17 :- Faulting in the truck lane
Fig.18 :- Up close near a bus stop
Description: A difference in elevation across a joint or crack usually associated with
undoweled JPCP. Usually the approach slab is higher than the leave slab due to pumping, the
most common faulting mechanism. Faulting is noticeable when the average faulting in the
pavement section reaches about 2.5 mm (0.1 inch). When the average faulting reaches 4 mm
(0.15 in), diamond grinding or other rehabilitation measures should be considered (Rao et al.,
1999).
Problem: Roughness
Possible Causes: Most commonly, faulting is a result of slab pumping. Faulting can also be
caused by slab settlement, curling and warping.
23. Repair: Faulting heights of less than 3 mm (0.125 inch) need not be repaired. Faulting in an
undoweled JPCP between 3 mm (0.125 inch) and 12.5 mm (0.5 inch) is a candidate for a dowel
bar retrofit. Faulting in excess of 12.5 mm (0.5 inches) generally warrants total reconstruction.
5.Joint Load Transfer System Deterioration
Fig.19 : - Exposed failure with rusted dowel bars
Fig.20 :- Patched Failure
Description: Transverse crack or corner break developed as a result of joint dowels.
Problem: Indicator of a failed load transfer system, roughness
Possible Causes: Load transfer dowel bars can fail for two principal reasons:
Corrosion. If inadequately protected, dowel bars can corrode over time. The
corrosion products occupy volume, which creates tensile stresses around the dowel
bars, and a severely corroded dowel bar is weaker and may fail after repeated loading.
Misalignment. Dowel bars inserted crooked or too close to the slab edge may create
localized stresses high enough to break the slab. Misalignment can occur during
original construction or during dowel bar retrofits.
Repair: Removal and replacement of the affected joint load transfer system followed by a fulldepth patch for affected area.
24. 6.Linear (Panel) Cracking
Fig.21 :- Large panel crack
Fig.22 :- Panel cracks on a residential street
Fig.23 :-Panel cracking in the truck lane
Description: Linear cracks not associated with corner breaks or blowups that extend across
the entire slab. Typically, these cracks divide an individual slab into two to four pieces.
Problem: Roughness, allows moisture infiltration leading to erosion of base/subbase support,
cracks will eventually spall and disintegrate if not sealed
25. Possible Causes: Usually a combination of traffic loading, thermal gradient curling, moisture
stresses and loss of support.
Repair: Slabs with a single, narrow linear crack may be repaired by crack sealing. More than
one linear crack generally warrants a full-depth patch
7.Patching
Fig24 :- Patch on a residential street
Fig.25 :- Large utility patch
Fig.26 :- Patch with poor edges
Description: An area of pavement that has been replaced with new material to repair the
existing pavement. A patch is considered a defect no matter how well it performs.
Problem: Roughness
26. Possible Causes:
Previous localized pavement deterioration that has been removed and patched
Utility cuts
Repair: Patches are themselves a repair action. The only way they can be removed is through
an overlay or slab replacement.
8.Polished Aggregate
Fig.27 :-Aggregate after almost 40 years of wear
Fig.28 :- A closer look
Description: Areas of PCC pavement where the portion of aggregate on the surface contains
few rough or angular aggregate particles.
Problem: Decreased skid resistance
Possible Causes: Repeated traffic applications. Generally, as a pavement ages the protruding
rough, angular particles become polished. This can occur quicker if the aggregate is susceptible
to abrasion or subject to excessive studded tire wear.
Repair: Diamond grinding or overlay.
27. 9.Popouts
Fig.29 :-Large popouts
Fig.30:-Popout close-up
Description: Small pieces of PCC that break loose from the surface leaving small divots or
pock marks. Popouts range from 25 - 100 mm (1 - 4 inches) in diameter and from 25 - 50 mm (1
- 2 inches) deep.
Problem: Roughness, usually an indicator of poor material
Possible Causes: Popouts usually occur as a result of poor aggregate durability. Poor
durability can be a result of a number of items such as:
Poor aggregate freeze-thaw resistance
Expansive aggregates
Alkali-aggregate reactions
Repair: Isolated low severity popouts may not warrant repair. Larger popouts or a group of
popouts can generally be repaired with a partial-depth patch.
28. 10.Pumping
Fig.31:-Pumping in action Fig.32 :-Pumping evidence during HVS test Fig.33:-Pumping
11.Punchout
Fig.34:-Severe punchout
Description: Localized slab portion broken into several pieces. Typically a concern only with
CRCP.
Problem: Roughness, allows moisture infiltration leading to erosion of base/subbase support,
cracks will spall and disintegrate.
Possible Causes: Can indicate a localized construction defect such as inadequate
consolidation. In CRCP, it can be caused by steel corrosion, inadequate amount of steel,
excessively wide shrinkage cracks or excessively close shrinkage cracks.
Repair: Full-depth patch.
29. 12.Reactive Aggregate Distresses
Fig.35 :-Severe crazing
Description: Pattern or map cracking (crazing) on the PCC slab surface caused by reactive
aggregates. Reactive aggregates are those that either expand or develop expansive by products
when introduced to certain chemical compounds.
Problem: Roughness, an indication of poor aggregate - will eventually lead to PCC slab
disintegration.
Possible Causes: This type of distress is indicative of poor aggregate qualities. Most
commonly, it is a result of an alkali-aggregate reaction.
Repair: Partial-depth patch for small areas of scaling or slab replacement for large areas of
scaling.
13.Shrinkage Cracking
Fig.36: - Shrinkage Cracking
30. Description: Hairline cracks formed during PCC setting and curing that are not located at
joints. Usually, they do not extend through the entire depth of the slab. Shrinkage cracks are
considered a distress if they occur in an uncontrolled manner (e.g., at locations outside of
contraction joints in JPCP or too close together in CRCP).
Problem: Aesthetics, indication of uncontrolled slab shrinkage. In JPCP they will eventually
widen and allow moisture infiltration. In CRCP, if they are allowed to get much wider than
about 0.5 mm (0.02 inches) they can allow moisture infiltration (CRSI, 1996).
Possible Causes: All PCC will shrink as it sets and cures, therefore shrinkage cracks are
expected in rigid pavement and provisions for their control are made. However, uncontrolled
shrinkage cracking can indicate:
Contraction joints sawed too late. In JPCP, if contraction joints are sawed too late the
PCC may already have cracked in an undesirable location.
Poor reinforcing steel design. In CRCP, proper reinforcing steel design should result
in shrinkage cracks every 1.2 - 3 m (4 - 10 ft.).
Improper curing technique. If the slab surface is allowed to dry too quickly, it will
shrink too quickly and crack.
High early strength PCC. In an effort to quickly open a newly constructed or
rehabilitated section to traffic, high early-strength PCC may be used. This type of
PCC can have a high heat of hydration and shrinks more quickly and to a greater
extent than typical PCC made from unmodified Type 1 portland cement.
Repair: In mild to moderate severity situations, the shrinkage cracks can be sealed and the slab
should perform adequately. In severe situations, the entire slab may need replacement.
Shrinkage cracks on brand new slabs
Severe shrinkage cracking
31. 14.Spalling
Fig.37:-Linear crack spalling
Fig.38:-Spalling from a bad construction joint
Description: Cracking, breaking or chipping of joint/crack edges. Usually occurs within
about 0.6 m (2 ft.) of joint/crack edge.
Problem: Loose debris on the pavement, roughness, generally an indicator of advanced
joint/crack deterioration
Possible Causes: Possible causes are (AASHTO, 1993):
Excessive stresses at the joint/crack caused by infiltration of incompressible materials
and subsequent expansion (can also cause blowups).
Disintegration of the PCC from freeze-thaw action or "D" cracking.
Weak PCC at a joint caused by inadequate consolidation during construction. This
can sometimes occur at a construction joint if (1) low quality PCC is used to fill in the
last bit of slab volume or (2) dowels are improperly inserted.
Misalignment or corroded dowel.
Heavy traffic loading.
32. Repair: Spalling less than 75 mm (3 inches) from the crack face can generally be repaired with
a partial-depth patch. Spalling greater than about 75 mm (3 inches) from the crack face may
indicated possible spalling at the joint bottom and should be repaired with a full-depth patch.7
33. CHAPTER -3
METHDOLOGY
3.0HIGHWAY MAINTENANCE
Roads are of vital importance in order to make a nation grow and develop. Especially in
the Third world, good maintained roads also will enhance poverty reduction by improving
accessbetween regional and rural communities and, ultimately, enhancing socio-economic
growth and development. Road networks form vital links between production centersand
markets. In Addition its multiple function of providing access to employment, social, health and
education Services makes road network crucial in fighting against poverty by opening up more
areas and Stimulating economic and social development.
There is a problem, however, which is common throughout the world, the neglect of
maintaining our roads. Building new roads cost money, but without maintaining the roads
properly, they deteriorate very quickly. If nothing is done, roads with a design life of decades can
need replacing or major repair work after just a few years. That deterioration will very fast infect
road transport in general where the costs will soar, This again will infect the economy of the
transporters. The transporters will transfer their Expenses to the customers and the economy of
the whole country will suffer. As the road Network deteriorates, the whole country loses major
assets build up over years, assets created With vast amounts of money, time and effort.
Yet even small budgets for maintenance make a difference with proper planning and the
right Priorities. The situation in many countries concerning the road condition is not only urgent,
it is critical. It is important to know the costs involved in road maintenance and the costs of not
maintaining the roads. The money which is saved in the maintenance budget by not maintaining
the roads, is ultimately paid by the users and the society. I will call it the invisible
Tax, and the total cost to the economy is huge.
In most countries it is believed to be a political benefit to be in favour of investing money in
Building new roads. However, maintenance does not have the same status or does not give the
same opportunity to stake holders or decision makers to present themselves to the public.
Something has to be done with this situation. We as professional people have to sell the message
that maintaining roads are of decisive importance for a country.
34. The overall purpose of highway maintenance is to fix defects and preserve the pavement's
structure and serviceability. Defects must be defined, understood, and recorded in order to select
an appropriate maintenance plan. Defects differ between flexible and rigid pavements.
3.1MaintenanceAccording to Haas (1978) the definition of maintenance varies among agencies. In a
physical sense, maintenance consists of a set of activities directed toward keeping a structure in a
serviceable state. For pavement, this includes such work as patching, crack, filling and so on.
Following are some definition of maintenance from different sources.
i. Definition from BS3811 : 1984 describes maintenance as combination of Technical and
management work done on a specific asset or structure to Ensure the structure is in good
condition and is functioning at its maximum capacity .
There are two types of maintenance:
Maintenance involving repairing work
Maintenance involving prevention work.
Reparation can be described as rehabilitation or replacement of spoiled components meanwhile
prevention is to prevent defects from occurring.
ii. Definition from Oxford Advance Learner’s English Dictionary describes maintenance as the
action of maintaining something or the state of being maintained.
iii. From Majdi, et al (2002), definition of pavement maintenance can be described as methods
and techniques used to restore or maintain a specified level of service and to prolong pavement
life by slowing its deterioration rate. As a summary, the main and only objective of maintenance
is to ensure the specific structure being maintained is in a good and acceptable condition and will
not cause inconvenience to the users. 8
3.2Main Objectives of Highway Maintenance:
Repair of functional pavement defect.
Extend the functional and structural service life of the pavement.
Maintain road safety and signage.
35. keep road reserve in acceptable condition
Through routine maintenance practices, highway systems and all of their components can be
maintained to their original, as-built condition.2
3.3Road MaintenanceProper road maintenance contributes to reliable transport at reduced cost, as there is a direct
link between road condition and vehicle operating costs (VOC). An improperly maintained road
can also represent an increased safety hazard to the user, leading to more accidents, with their
associated human and property costs. In general, road maintenance activities can be broken into
four categories:
Routine works. These are works that are undertaken each year that are funded from the
recurrent budget. Activities can be grouped into cyclic and reactive works types. Cyclic works
are those undertaken where the maintenance standard indicates the frequency at which activities
should be undertaken. Examples are verge cutting and culvert cleaning, both of which are
dependent on environmental effects rather than on traffic levels. Reactive works are those where
intervention levels, defined in the maintenance standard, are used to determine when
maintenance is needed. An example is patching, which is carried out in response to the
appearance of cracks or pot-holes.
Periodic works. These include activities undertaken at intervals of several years to preserve
the structural integrity of the road, or to enable the road to carry increased axle loadings. The
category normally excludes those works that change the geometry of a road by widening or
realignment. Works can be grouped into the works types of preventive, resurfacing, overlay and
pavement reconstruction. Examples are resealing and overlay works, which are carried out in
response to measured deterioration in road conditions. Periodic works are expected at regular,
but relatively long, intervals. As such, they can be budgeted for on a regular basis and can be
included in the recurrent budget. However, many countries consider these activities as discrete
projects and fund them from the capital budget.
Special works. These are activities whose need cannot be estimated with any certainty in
advance. The activities include emergency works to repair landslides and washouts that result in
the road being cut or made impassable. Winter maintenance works of snow removal or salting
36. are also included under this heading. A contingency allowance is normally included within the
recurrent budget to fund these works, although separate special contingency funds may also be
provided.
Development. These are construction works that are identified as part of the national
development planning activity. As such, they are funded from the capital budget. Examples are
the construction of by-passes, or the paving of unpaved roads in villages.9
3.4Maintenance of Earth RoadsRoad maintenance is characterized as the continuing care of the roadway and providing
for its intended use until such time as needed improvements are identified and undertaken.
Within the scope of recurrent and deferred maintenance activities, opportunities are identified to
improve cost effectiveness of surfacing and ditch maintenance and reduce future capital
improvements. The selection of equipment, materials and procedure is either a commitment to
long-term transportation system goals or they create future constraints. 10
Problems occurred in earth roads areFormation of dust in dry weather.
Formation of longitudinal ruts along wheel path or vehicles.
Formation of cross ruts along surface after monsoon.
Damage caused in earth roads need frequent maintenance and dust nuisance can remedied
by-
Periodic sprinkling of waterSpreading water periodically in winter season overcome problem of dust very effectively.2
Use of Dust PalliativesDust palliatives are substances applied to a road surface to reduce airborne dust. They
may be applied every few hours on a busy construction site, or every few years at a site with
little traffic. There are many, many kinds of dust palliatives, and many companies produce
them. It’s big business, because ―fugitive dust‖ must be controlled at many construction and
industrial sites across the nation. The basic categories of dust palliatives include water, water
37. absorbing products, petroleum based products, and organic nonpetroleum based products,
electrochemical products, polymer products, synthetic fluids, enzymes, and clay additive
products. Palliative used are, Water Absorbing Products (deliquescent salts) - calcium
chloride, magnesium chloride, molasses/sugar beet products, animal fats, vegetable oils.
Palliatives WorkSome Palliatives Work by Increasing Moisture Content Moisture in the surface of dirt
roads causes particles to stick together. The moisture content of dirt roads can be increased
either through spreading water or application of salts which attract water. Though water is
available in almost all Alaskan communities, moving water to unpaved roads can be a
problem. Larger communities may have water trucks to take advantage of local water
supplies. Smaller communities may not have such equipment. When water can be applied, it
only provides a short term reduction in dust. Regular, light watering is better than less
frequent, heavy watering. The application of deliquescent salts to road surfaces can control
road dust. A deliquescent salt, like calcium or magnesium chloride, absorbs water from the
air. Soils treated with these salts have a higher water content than untreated soils. Slippery
wet roads and vehicle corrosion are disadvantages of salt application. Also, rainfall
eventually removes salts from the roadway. 11
Treatment with calcium chloride (cacl2)Due to the hygroscopic nature of mix it retains water so prevents water to enter in
subbase or subgrade of road then save road from damage. An effective maintenance
management system helps identify and prioritize needed improvements. Planning, scheduling
and performing roadside ditch, travel way and shoulder maintenance requires knowledge and
expertise to be successfully and economically accomplished. Basic maintenance approaches
and concepts are suggested and new considerations proposed for aggregate, earth and native
surfaced roads.2
3.5Maintenance of Water Bound Macadam Roads:
38. Most of the driveways built today are those which are known as Telford roads. These are
usually constructed of twelve inches of stone over all. An eight-inch foundation is provided of
hard quarry stone, laid on edge, with the longest dimension placed at a right angle to the side line
of the drive. Very often this large stone can be found on the property. After the stones are placed
they should be gone over with napping hammers and made fairly even by breaking off the
irregular edges; the pieces of stone so broken off should be used to fill in chinks. Over this
should be placed three inches of one and one-half inch stone. Then a light covering of threequarter inch stone may be placed as a binder and finished with clean breaker dust. The drive
should be rolled before and after placing the three-quarter inch stone, with a roller weighing not
less than five tons. The three-quarter inch stone and the dust should never be mixed together; the
dust will work through and the stone find the surface, making it rough and troublesome. When
rolling the finished surface it should be wetted constantly until a wave of water appears in front
of the roller.
Fig.39 :- Water Bound Macadam’s Road.12
Damage of Water Bound Macadam Roads is caused due to Heavy mixed traffic
Adverse climatic conditions
Due to combined effect of traffic and rain water washing away soil binder from
surface
39. Stone aggregates protrudes out or get loose on surface layers.2
The maintenance of water bound macadam surface consists of :
Dust nuisance can be prevented by providing bituminous surface on WBM pavements.
Filling potholes ruts with additional material and adequately compacting.
Removing corrugations by dragging.
Repairing leveled surface (in which loose aggregates appear on the road) by adding fresh
binding material, watering and compacting.
Restoring broken edges by fresh material.
Renewal of surface (50-75 mm) once in 2-6 years depending upon traffic.
3.6Maintenance of Bituminous Surfaces-
Bituminous Surface Treatments (BST)
Wearing surface that is applied to a pavement or base course. BSTs can provide all of the
following:
A water proof layer to protect the underlying pavement.
Increased skid resistance.
A fill for existing cracks or raveled surfaces.
An anti-glare surface during wet weather A bituminous surface treatment, also known
as a seal coat or chip seal, is a thin protective and an increased reflective surface for
night driving.
3.6.1A single layer BST is constructed in the following steps:
40. 1. Surface preparation. Surface defects, such as potholes, are repaired and the existing
surface is cleaned (e.g., by a street sweeper).
2. Asphalt material application. Typically, an asphalt emulsion is applied from a spray
truck to the surface of the existing pavement .
3. Aggregate application. A thin aggregate cover (only one stone thick) is spread over
the asphalt material before it has set .The aggregate usually has a uniform gradation.
4. Aggregate embedding. A roller (usually a pneumatic tire roller) is used to push the
aggregate into the asphalt material and seat it firmly against the underlying pavement
Generally, about 50 percent of each aggregate particle should be embedded in the
asphalt material after final rolling. About 70 percent of each aggregate particle will
be embedded after several weeks of traffic. It is common to place an aggregate
"chokes tone" on top of the uniformly graded larger aggregates after embedment.
Choke stone is essentially a finer aggregate gradation (e.g., less than 12.5 mm (0.25
inches)) used to make a more dense aggregate matrix at the level of embedment .
This more dense matrix helps prevent excessive aggregate loss due to traffic.
Purpose: Preventive maintenance.Wearing course, waterproof covering for the existing
pavement.
Materials: Asphalt (as asphalt binder, cutback asphalt or asphalt emulsion) and aggregate
(uniformly graded).
Patches: Patches are a common method of treating an area of localized distress. Patches can
be either full-depth where they extend from the pavement surface to the subgrade (see Figure
10.12) or partial where they do not extend through the full depth of existing pavement .
Full-depth patches are necessary where the entire depth of pavement is distressed. Often times,
the underlying base, subbase or subgrade material is the distresses root cause and will also need
repair. Partial depth patches are used for pavement distresses like raveling, rutting, delaminating
and cracking where the depth of crack does not extend through the entire pavement depth.
41. Patching material can be just about any HMA or cold mix asphalt material as well as certain
types of slurries. Typically some form of HMA is used for permanent patches, while cold mix is
often used for temporary emergency repairs.
3.6.2 Semi-Permanent Pothole Patch Remove all water and debris from the pothole.
Square up the pothole sides so they are vertical and have in-tact pavement on all sides.
Place the patching material into the clean squared-up hole. The material should mound in
the center and taper down to the edges so that it meets flush with the surrounding
pavement edges.
Compact the patching material starting in the center and working out toward the edges.
Compaction can be accomplished using a vibratory plate compactor or a single-drum
vibratory roller. Check the compacted patching material for a slight crown. This is done
so that subsequent traffic loading will compact it down to the surrounding pavement
height.
3.6.3Throw-and-roll Place the patching material into the pothole without any preparation or water/debris
removal.
Compact the patching material using the patching truck tires (usually 4 to 8 passes).
Check the compacted patch for a slight crown. If a depression is present add more
patching material and compact.
Although it may seem that the semi-permanent technique would produce a higher quality
patch than the throw-and-roll technique, the FHWA's Long Term Pavement Performance (LTPP)
Study found that the "throw-and-roll technique proved just as effective as the semi-permanent
procedure for those materials for which the two procedures were compared directly" (FHWA,
1998). Since the semi-permanent technique is more labor and material intensive, the throw-androll technique will generally prove more cost effective if quality materials are used.13
42. 3.6.4 Asphalt Resurfacing
Asphalt surfaces have a typical service life of 8 to 12 years, depending on traffic and
weather conditions. Asphalt resurfacing is necessary when the asphalt surface has reached the
end of its service life or if other methods of restoration cannot repair the roadway. A new asphalt
surface will improve driving conditions as well as the aesthetics of the roadway. Asphalt
resurfacing is a multi-step process that usually involves several work crews, accompanied by
proper construction signs and work-zone traffic control measures to maintain public safety.
Resurfacing an asphalt roadway requires the following steps:
Adjustment (lowering) of utilities to allow milling machines to traverse the roadway
without damaging utility assets.
Removal (milling) of old surface using a milling machine. All milled surfaces must be
cleaned by the milling contractor and marked appropriately to safely direct traffic.
(Milling may not be required on streets with no curb and gutter; however, the edges of
streets with no curb and gutter may be trimmed prior to milling in order to provide a
more uniform milled surface.)
Re-adjustment (raising) of utilities so that they will again be flush with the new surface
that will be applied.
Application of a tack coat to milled surface to serve as a binder for the new surface that
will be applied.
Application of new paving surface by paving machines.
Application of new thermal plastic pavement markings on new pavement surface
3.6.5Rejuvenation
Rejuvenation is a preventive maintenance technique applied to newly paved streets to
replenish lighter oils and rejuvenate the roadway in order to prolong its service life. Because the
cost of applying surface treatments is minimal compared to resurfacing the roadway, Metro
makes an effort to utilize surface treatments to extend the service life of streets throughout
Davidson County
43. Rejuvenation Process includes following steps:
Before surface treatment can be applied, the roadway must be cleaned. A power broom is
used to clean the roadway surface.
The surface treatment will be applied from a distributor truck.
Workers will manually spray corners and hard to reach areas.
The street will be covered with a layer of sand for approximately 24 hours while the
surface treatment cures.
The sand will be swept by the contractor.
3.6.6Crack Sealing
Over time, sunlight oxidizes the oils in asphalt, causing the asphalt to become brittle and
develop cracks. Cracks in asphalt roadways provide a place for moisture to reach the pavement
base and will ultimately lead to more extensive deterioration. Crack sealing is a maintenance
method to repair construction joints, and longitudinal cracks in the roadway. Crack sealing is
necessary to prevent water from entering the base of the roadway, which could require major
reconstruction.
The Crack Sealing Process includes the following steps:
The cracks in the roadway may be cut out to a specified depth.
The workers will clean and dry the open roadway cracks with high-pressure air and heat.
A hot-pour crack sealant will be applied.
Sand will be placed over the sealant to reduce stickiness.14
3.7Cement Concrete road Maintenance / RepairConcrete is used in roads, highways and airport pavements because of its load carrying
capacity and low maintenance. Better knowledge of speedy repair techniques would be a further
advantage in supporting the use of concrete pavements. This report examines the repair and
restoration of concrete pavements systematically by distress classification and the underlining
objectives of each concrete repair and restoration technique. It also covers the composition and
44. characteristics of a broad range of repair materials for cracks, spalling, potholes, rough patches
and sunken slab. The review covers techniques used in routine maintenance of concrete
pavements but excludes slab replacement. Emphasis will be given to road pavements but they are
also applicable to other concrete pavements.
Structural distress
Structural distress affects the pavement capacity to carry the traffic. Cracking and joint
deterioration are typical structural distresses. Cracks that extend through the depth of a slab are
structural cracks. They are unplanned and can occur as longitudinal, transverse, corner, or
intersecting cracks. They can be caused by loading, excessive joint-spacing, shallow or late joint
sawing, base or edge restraint, and joint lock-up. Pumping of the subbase/subgrade, curling and
warping of the slab, or culvert or utility trench subsidence can also cause cracking. Corner breaks
and intersecting cracks indicate that a slab has marginal support developed when heavy loads
cause large vertical deflections at the slab edges or corners, and pump fines from beneath the
slab. Other causes including curling and warping of the slab because of temperature and moisture
gradients; heaving and swelling of frost- or moisture-susceptible soils; and settling of backfill
over culverts or underground utility structures.
Joint deteriorations --such as spalling, breaking, cracking, chipping, or fraying of the slab
edges usually occur within 50 mm of joints. Such deterioration starts when incompressible center
and become lodged in the joints or cracks during cool weather. As the temperature rises, the
slabs expand, causing high compressive stresses in the concrete which results in joint
deterioration. The deterioration results in more incompressible entering the joint or crack causing
further deterioration.
Punchouts- mainly occurs in continuously reinforced concrete pavements (CRCP). They occur
between two closely spaced transverse cracks that split at the longitudinal edge or joint. They
develop when high deflections at the pavement edge or longitudinal joint pump subbase material
from beneath the slab and cause a loss of support. Further loading creates a cantilever action,
which eventually ruptures the longitudinal steel at the crack faces. Continued loading pushes the
small segment of concrete into the subbase and causes a punchout.
45. Durability Distress
Durability distress is caused by the premature deterioration of concrete such as D-cracking and
alkali-aggregate reaction (AAR).
D-cracking- is D-shaped hairline cracks that occur near joints, cracks, and free edges when
certain aggregates in a concrete become saturated, freeze, and expand. The expansion causes the
surrounding concrete matrix to crack.
Alkali-Aggregate reaction- is caused by a chemical reaction that occurs when free alkalis
in the concrete combine with certain siliceous aggregates to form an alkali-silica gel. As the gel
forms, it absorbs water and expands, which cracks the surrounding concrete. For further
Functional distress:Functional distress affects the ride quality and safety of the pavement. It includes roughness,
noise and surface polishing.
Roughness is mainly caused by faulting – a difference in elevation between slabs at joints or
cracks. Faulting is caused by differential load transfer inducing high deflections at theslab
corners, resulting in the support material being pumped from under the slab or movedfrom one
side of the joint to the other. Roughness can also be built into a pavement duringconstruction.
Two other sources of roughness are heaving/swelling of frost- or moisturesusceptiblesoils and
settlement over culverts or underground utilities.
Surface polishing is the wearing away of the surface texture to expose the concrete coarse
Aggregate on heavily trafficked pavements. It leaves the surface smooth and reduces the
pavement’s skid resistance and surface friction capabilities.
Noise is defined as 'unwanted sound' and is typically described as a high-pitched sound. The
main source of the noise is the surface/tyre interaction that develops when a vehicle speed
exceeds 55 km/h on pavements with certain surface texture such as uniformly spaced transverse
tining.
Surface defects comprise scaling, popouts, crazing, and plastic shrinkage cracking. Scalingis
caused by overworking the surface; popouts are due to reactive or absorptive aggregates; while
46. crazing and plastic shrinkage cracking are usually the result of poor curing procedures.Such
distresses may affect the pavement’s ride and noise characteristics. information on minimizing
the risk of AAR damage to concrete.
Repair Methods
There are a range of concrete repair and restoration techniques which are used as
corrective, preventive, and corrective-and-preventive measure. They can be used individually but
are typically more effective when several are used together. Although concrete repair and
restoration does not necessarily increase structural capacity of a pavement, it does extend the
pavement’s service life.
Corrective Techniques :Corrective techniques are used to repair a given distress and improve the serviceability of the
pavement.
Full-depth repairs Full-depth repairs fix cracked slabs and joint deterioration by removing at
least a portion of the existing slab and replacing it with new concrete. This maintains the
structural integrity of the existing slab and pavement. Full-depth repair is also appropriate for
shattered slabs, corner breaks, punchouts in CRCP, and some low-severity durability problems. It
involves marking the distressed concrete, saw cutting around the perimeter, removing the old
concrete, providing load transfer, and placing new concrete. Each repair must be large enough to
resist rocking under traffic, yet small enough to minimize the amount of patching material.
More-detailed information can be found in the ACPA Guidelines for Full Depth Repair 4 or the
Queensland Transport Pavement Rehabilitation Manual5. Full-depth precast concrete slab repairs
were trialled by the Ministry of Transportation Ontario (MTO) in 2004 using three proprietary
methods and are reported on by Lane and Kazmierowski6. The methods differ in how the base is
prepared and how the precast slabs are installed and dowelled to the adjacent concrete slabs.
Following the construction, nondestructive testing was undertaken to assess the load transfer
efficiency at the pavement joints and detect loss of support beneath the slab. The overall
assessment by the MTO was that the precast trials went well. The work was carried out within
the required time frames and seems to be performing well. The precast repairs are similar in both
ride and appearance to fast-track repairs made along the same section of highway. Some surface
47. tolerance requirements were not met, but diamond grinding would improve the ride. The report
includes recommendations were given to help future precast concrete repairs go as smoothly as
possible.
Partial-depth repairs Partial-depth repairs correct surface distress and joint/crack
deterioration in the upper third of a concrete slab. When the deterioration is greater in depth or
reaches embedded steel, a full-depth repair must be used instead. It involves removing the
deteriorated concrete, cleaning the patch area, placing new concrete, and reforming the joint
system. More-material detailed information can be found in the ACPA Guidelines for Partial
Depth Repair7. RTA QA Specification M2248 was developed specifically for the non-structural
repair of surface spalls in concrete pavement. The area to be repaired should have dimensions of
at least 100 mm and extend 20 mm beyond the deteriorated concrete. M224 specifies that the
repair must: have its largest aggregate no greater than one third of the minimum depth of the
repair; bond permanently with the base concrete without cracking; be UV stable, non-shrink and
none expansive; cure and harden within the time specified; and be of similar colour to the
surrounding wearing surface when cured.
Cracking and seating This technique is used prior to placing an asphalt or concrete overlay
to control reflective cracking in the overlay. It is sometimes referred to as pavement breaking or
pavement shattering. It is intended to create concrete pieces that are small enough to reduce
horizontal slab movement to a point where thermal stresses which contribute to reflective
cracking will be greatly reduced, yet still be large enough and still have some
Aggregate interlock between pieces so that the majority of the original structural strength of
PCC pavement is retained. It is used to re-establish support between the subbase and the slab
where there may be voids.
A nationwide survey conducted by the Florida Department of Transportation (FDOT9) indicated
that most states have a relatively-small number of cracking and seating (rubblized) sections,
although three states have over ten sections each. The construction techniques, overlay
thicknesses, and field performance varied from state to state. However, it was clear that most
states were highly satisfied with rubblization as a means of eliminating reflected cracks.
Problems were mainly due to weak subgrade. Guidance on design, construction and specification
48. of cracking and seating, is given in the Queensland Transport Pavement Rehabilitation Manual5
and the US Federal Highway Administration Pavement Rehabilitation Manual3.
3.2 Preventative Techniques : Preventative techniques are proactive activities that slow or prevent the occurrence of a
distress in order to maintain serviceability.
Joint and crack resealing Joint and crack resealing minimizes the infiltration of surface
Water and incompressible material into the joint system. Minimizing water infiltration reduces
subgrade softening; and slows pumping and erosion of subgrade or subbase fines. Minimizing
incompressible reduces the potential for spalling and blow-ups.
RTA QA Specification M21510 was prepared specifically for the routing and sealing of
cracks in concrete pavement as a combined activity. It applies where the width of cracking (or
longitudinal joint opening) is at least 1 mm or the surface arris is spalled. It suggests the use of
urethane as a substitute for silicone sealant where distillate fuels are likely to be in concentration.
The Queensland Transport Pavement Rehabilitation Manual5 summarises some of the
proprietary crack filler products commonly available and their properties.
Retrofitting concrete shoulders Retrofitting concrete shoulders adds a tied concrete
shoulder to an existing pavement. It is similar to dowel-bar retrofit because it decreases the
critical edge stresses and corner deflections and reduces the potential for transverse cracking,
pumping, and faulting. On CRCP, retrofit concrete shoulders can decrease the outside pavement
edge deflection and cantilever action, which reduced the potential for punchouts.
Retrofitting edge drains Adding a longitudinal drainage system to a pavement aids in the
rapid removal of water and may prevent pumping, faulting, and durability distress from
Developing.
3.3 Corrective-and-preventative Techniques Corrective-and-preventative techniques
are used to repair and slow down or prevent the occurrence of a given distress and improve the
serviceability of the pavement.
49. Diamond grinding Diamond grinding improves a pavement ride by creating a smooth, uniform
profile by removing faulting, slab warping, studded tyre wear, and patching unevenness. This
extends the pavement’s service life by reducing impact loadings, which can accelerate cracking
and pumping. More detailed information can be found in the ACPA Diamond Grinding and
Concrete Pavement Restoration 200011.
Dowel-bar retrofit Dowel-bar retrofit increases the load transfer efficiency at transverse
cracks and joints in PCP and JRCP pavements by linking the slabs together so that the loadis
distributed evenly across the joint. Improving the load transfer increases the pavement’s
structural capacity and reduces the potential for faulting.
Slab undersealing Slab under sealing is a means to stabilize existing pavement slabs by
filling small voids beneath the slab and base or base and subbase. The under sealing is intended
to restore slab support and does not include the lifting of the pavement slab (slab jacking) to a
prescribed elevation or to an original profile. Several grouts have been trialled and Portland
cement grout was found to produce best results. Guidance on design, construction and
specification of slab undersealing is given in the Queensland Transport Pavement Rehabilitation
Manual5 and the US Federal Highway Administration Pavement Rehabilitation Manual3.
Cross-stitching Cross-stitching is used to repair longitudinal cracks that are in a fair
condition. It increases load transfer at the crack by adding steel reinforcement to restrict
widening of the crack. It is not an alternative for cracks that are severely deteriorated or
functioning as a joint.
Grooving Grooving restores skid resistance to concrete pavements. It increases the surface
friction and surface drainage capabilities of a pavement by creating small longitudinal or
transverse channels that drain water from underneath the tyre, reducing the hydroplaning
potential.15
