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Complete report1123121

  1. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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
  50. 50. REFRENCE 1 2 book. Sk khanna $ c.e.g. justo (highway engg.) 3 4 5 2_body.htm 6 QFjAA& =xb8PU4rwKoH-rAe5s4HgAQ&usg=AFQjCNHD8CrmCmiC4_sAfNAgYkiPYTyLw&bvm=bv.61965928,d.bmk 7 8 9 10 11 12 13
  51. 51. 14 15