Conceptual Maintenance and Rehabilitation Strategies

Dr. S.S.Seehra Former Director Grade Scientist & Head, Rigid Pavements Division, CRRI Chief Consultant–Pavement and Geotech, Span Consultant Pvt. Ltd. New Delhi

Introduction

Highway maintenance is an important activity of every highway department. The safety and convenience of traffic using the road are governed to a large extent by the quality of maintenance. The operation – economics of road transport is influenced by the degree of maintenance imparted to the road. The life of an asset can be preserved and prolonged if adequate maintenance measures are undertaken well in time. In developing countries, stage construction of pavements is often resorted to, with lesser pavement thickness and lower specifications than needed for a full design. The proper maintenance of roads, therefore, assumes greater significance in such situations.

This paper emphasizes the need for conceptual mechanism that will ensure the maintenance management procedures to be planned timely with adequate preventive maintenance interventions for effective sustainability of these roads. The financial resources at the command of a maintenance engineers are always short of demands, and it becomes necessary to utilize the same in the most judicious manner, by applying the best engineering practices and managerial skills. Poor road drainage and particularly failure to prevent ingress of water into the subgrade and into the lower pavement layers is considered to be the single main culprit of road failures in India. Maintenance of the drainage system is usually a relatively low cost operation, and one which can significantly reduce the need for far more costly pavement repairs and rehabilitation.

Road maintenance is an essential activity to rejuvenate roads in the safest condition, and to ensure that Pavement Management System (PMS) should also be an integral part of a larger overall Road Maintenance Management System (RMMS).

Need for Maintenance

A bituminous surface deteriorates with the passage of time owing to

1. The action of traffic, especially of overloading of heavy commercial vehicles.
2. Environmental factors, such as ingress of water, oxidation of the binder and loss of volatiles.
3. Inadequacies in the initial design, specifications and construction standards of the bituminous layers; and
4. Lack of adequate support from the lower pavement layers.

Timely and proper maintenance will prolong the life of a pavement system. Road maintenance is a routine, periodic and special activities to be performed to upkeep the pavement, shoulders and other facilities provided for road users, as nearly as possible in its constructed conditions under normal conditions of traffic and forces of nature.

Pavement Management Systems

Modern methods of highway maintenance make use of good management principles, which are invaluable aids in planning and programming of maintenance operations. Many Pavement Management Systems (PMS) have been developed and are extensively used worldwide. A PMS is a computer package, which facilitates advance planning of maintenance operations and optimal allocation of resources. It consists of the following elements

1. A basic road data bank, builtup and updated periodically by road inventories and condition surveys.
2. A pavement performance model, which predicts the future programme of a given pavement system.
3. A transportation cost model, which calculates the road user costs for the given condition of the pavement.
4. Selection of Intervention levels.
5. Prioritizing the maintenance needs (renewal and overlay) for a given budget.

Rehabilitation in a Pavement Management System

One of the major reasons that pavement design was historically considered as a one shot process was the lack of an adequate concept for dealing with performance. This need was filled by the serviceability performance concept. Thorough examination of actual highway pavement life histories indicates that this cycle process shown in Figure 1 is more realistic than the so-called one shot design method. As a matter of fact, almost no pavements can be found that serve out a predetermined design life of 20 years or more without some rehabilitation.

Maintenance Management Systems

For a modern road to operate efficiently and effectively for the benefit of all users, it is required to meet defined customer requirements. Maintenance operations and technologies themselves are evolving rapidly to meet the demands of modern road networks. Road drainage performance plays a vital role in ensuring the efficient structural performance of a pavement. Figure 2 illustrates a range of factors, which contribute to the deterioration of a road and to its consequent condition at any given time.

Development of Pavement Management Systems

Efficient and effective maintenance management is most simply expressed as doing the correct thing at the correct time and in the correct place. Pavement Management Systems are most effective if they fulfill a number of essential requirements in relation to the roads and road network to which they are applied. They can assist the engineer in identifying the most cost-effective appropriate treatment on selected sections of the road network through the use of economic analysis, predictive models and time series information. An effective management system must meet a number of core or critical requirements, too much sophistication should be viewed with caution and additional modules should be justified incrementally. Fundamental requirements of maintenance management planning stages are shown in Figure 3.

Maintenance of Flexible Pavements

To meet the various treatments needs of different pavement types, industry and research institutions have developed a range of materials and treatments to offer the engineer a wide variety of effective solutions. The materials are variously required to meet a number of criteria including strength, resistance to deformation, impermeability, good skidding resistance, low noise and spray generation, efficient drainage system, and value for money. Many modern materials offer a good range of these qualities, but it is fair to say that the perfect materials have yet to be developed. Figure 4 shows the pavement performance modeling which is also applicable to other forms of infrastructure behaviour.

Surface Defects and their Rectification

Pavement tend, under continued trafficking, to lose their anti-skid properties as the texture wears out and the stone aggregates get polished. The skid resistance of a surface may also be reduced by bleeding, or ‘fatting up’ of the road surface with excess bitumen. Many countries carry out skid resistance measurements as part of their maintenance needs assessment. Those pavement sections which have lost their anti-skid properties may be treated with a fresh surface treatment.

Simple maintenance procedure for correcting common distresses in flexible pavements including patching, crack and surface sealing through resurfacing. Skin patches, alligator cracks, deep patches, edge cracks, joint cracks, shallow depressions, hungry and caked surface, reflection cracking, shrinkage cracks and slippery cracks arriving from different technical conditions over a pavement are to be treated differently. This makes it increasingly necessary to find a method of common distress confinement and rehabilitation with a broad based applicability. Figure 5 shows the components of defectiveness profile recorded for surface treatment.

Assessment of Maintenance Needs

Maintenance needs are assessed every year as part of planning of maintenance. The assessment is done on the basis of condition surveys, which can take various forms such as :

• Visual rating
• Roughness measurements
• Benmkelman Beam Deflection measurements
• Skid Resistance Measurements

Visual rating is a simple method of inspecting the pavement surface for detecting and assessing the type and severity of the damage. Manifestation of distress or damage occurs in the form of; rutting, corrugations, ravelling, flushing, potholes, transverse cracking, longitudinal cracking, depressions, settlement, polished surface, streaking, hungry surface, edge cracking, reflection cracking, shrinkage cracking, deformation, slippage, shoving, stripping, disintegration, loss of aggregate, alligator cracking and edge failure etc. These serviceability indicators are to be kept intact through proper maintenance cycles methodology and strategies.

Preventive Bituminous Surface Maintenance through Micro-Surfacing

Future maintenance strategies for renewal surfacing activity is the need of the hour at regular intervals of time so that the constructed roads perform satisfactorily throughout their designed service life. Periodic renewals consist of the provision of micro-surfacing layer so as to preserve the required characteristics of the pavement and offset the wear and tear of the surface caused by traffic and weathering etc. Periodic renewals represent preventive maintenance, which is needed to prevent deterioration of the pavement characteristics and to ensure that initial qualities are kept up for the future requirements of traffic during the design life of the pavement. Early detection and repair of noticeable defects can prevent a major break down of the surface. For instance, if symptoms like hungry surface, raveling etc. are noticed at an early stage and suitable preventive action by way of renewal of surface is taken to arrest further deterioration, the life of the pavement can be prolonged. Micro-surfacing is a thin layer of a mixture of a modified bitumen based emulsion, aggregate, water and additives like cement and lime in desired proportions. Microsurfacing is generally applied over a hungry, baked flexible pavement surface and also in case of fretting of aggregate over already laid surface, shallow depressions and fine cracks to moderate cracks (3mm to 6mm wide).

It is relatively thin sections in which the mix is laid over the surface which is called microsurfacing. Micro-surfacing mix can be applied more frequently by machine application up to a thickness of 5mm in one application, where the situation demands there can be two applications of the same thickness. Micro-surfacing can be easily sweeped into cracks and fishers. Since a cationic type modified bitumen emulsion is used in preparing micro-surfacing the surfacing has got the unique feature of resisting action of water and preventing damage due to rains in the sealed pavement which may prove a good remedial measure. Micro-surfacing is a low cost preventive maintenance treatment that retards the deterioration of pavement surface caused by environmental and the associated oxidation of the existing surface. Micro-surfacing is now recognized as most cost-effectiveway to treat the deteriorated surface. The micro-surfacing treatment should only be used on structurally sound pavement without extensive cracking or other deterioration. This preventive maintenance treatment is applied in one or two courses and does not require compaction. Traffic can usually be located back on to the roadways within one hour under ideal condition. The micro surfacing mix provides excellent smoothness and good friction with minimal increase in pavement noise levels.

Micro-surfacing may be suitably used on cracked pavement in lieu of more conventional rehabilitation such as crack to sealing, fog seal, liquid seal and double surface treatments. Microsurfacing provides a convenient economical way of addressing pavement distress such as raveling and cracking.

Highway Design and Maintenance Standards

The World Bank had developed the highway design and maintenance standards model and its Version-3 has been in use. HDM-4 has been developed and released for use. For the proposed planning model, HDM-4 has been calibrated for Indian deterioration and user cost models and customized for the chosen computer system platform, which will bring the planning process to the state-of-the-art level. National Highway network maps can be digitized using Survey of India (SOI) base maps and the mapping data can be held in the Geographic Information System (GIS) format in a cartographic database. It may also be possible to overlay, the maps with all the other relevant information collected during the socio-economic, road condition and road inventory surveys. The entire highway management system needs to be established on a computer system platform on client server model at the headquarters of Ministry of Road Transport and Highways (MoRT&H). The regional centers could be linked with the headquarters through a communication system so as to enable data transfer from the field to the headquarters. Computer operating system can be selected to ensure compatibility of the hardware and the facility of upgradation at a later date. Software for GIS, HDM, image processing software, terrain modeling software, and Autocad may be required for the proposed planning model.

Future Suggestions of Road Maintenance

There is a need for the guidelines on the strategic maintenance of flexible pavements, which should be easy to use, understandable, and cost-effective and provide uniformity in evaluation, process and management methodology.

There is no doubt that the external influences which affect road operators and authorities will continue to play a major part in shaping the development of road maintenance. Indeed, it is probable that the most successful road maintenance will be that which is noticed least in terms of its impacts on the road user, the environment, and those living and working close to the carriageway. Some general indicators of future challenges for the road maintenance engineer are given below:-

1. Obtaining Good quality information about road conditions is an essential pre-requisite for sound decision making about the need for road maintenance, and type of treatment that is subsequently applied. Increased interest is likely to be paid to the concept of smart roads, which use sensors within road components to feed real – time information regarding their condition and performance.
2. A greater emphasis is also likely to be placed on improving communication with road users to provide them with up-to-date and reliable advice about the state of the road, including weather, traffic, safety and other conditions. Capabilities of this type could eventually form the basis of better highway maintenance control if the demand for limited road space grows excessively.
3. The very wide use of roads, and their impact upon those which they serve, offer great challenges to road maintenance engineers to ensure that theassets for whose upkeep they are responsible are maintained for the benefit and convenience of all the road users.
4. Most important aspect of the future is where does the future of Pavement Management Systems go from here? How can we upgrade and improve the technology of the Pavement Management System? How can we improve the Pavement Management System itself.
5. No existing system is directly applicable to another agency, do not be afraid to take advantage of the benefits of others experience. Much could be gained from expert sources with previous experience in the Pavement Management Systems.

• Efficient and effective maintenance management is simply expressed as doing the correct thing at the correct time and in the correct place.
• Making good decision regarding road maintenance is a complex process that involves the right treatment for the right road at a right time.
• A thin hot mix asphalt overlay on the principle of microsurfacing will improve the riding quality and skid
• resistance, revitalize the existing surface free of ruts and potholes, and other surface defects.
• The preventive maintenance approach through microsurfacing will not only save our scare funds but also provide a safe and comfortable ride to our road users.
• Micro-surfacing is one of the latest mixtures of surface treatments, such as chip seal, liquid seal, slurry seal and fog seal composed of polymer modified asphaltemulsion, crushed aggregates, mineral filler, water and field control additive as needed.
• The traffic on National Highways is likely to increaseenormously in the futuristic scenario. To meet the demand optimally, and thereby to ensure rapid economic progress of the country, it is essential to develop and establish an efficient highway planning and management systems. For this the existing deficiencies in the system need to be overcome and new capabilities need to be developed.
• Effort is also required to integrate various systems related to highway management system carried out in
• India and abroad. Committed manpower resources will have to be developed and adequate infrastructure will have to be established to bring the highway planning and management system to the state-of-the-art level and comparable to those existing in developed countries.
• Maintenance-by-Contract of National Highways and expressways should be privatized or as a part of construction contract to reduce the burden on the exchequer. The best possible way shall be to run pilot projects in every state and on National Highways and State Highways to start with.
• We should follow-up strict construction supervision and stringent quality control measures and must protect our investment with minimal maintenance costs.
• Proper pavement design, regular inspection and maintenance of drainage system is of utmost importance in preserving the investment made on the construction of highway pavements. The drainage conditions be improved along the highways so that the damage to the sub-grade due to seepage of water be avoided. The special attention is required for the maintenance of roads and highways in the snow and desert areas.
• The above highway maintenance strategies would be useful to reduce the losses caused due to bad condition of roads. The saving due toreduction in losses can be used for the construction of new roads and improvement of existingroads and highways.

1. Butler, B.C. and L.G. Byrd “Maintenance Management,” Section 25 of Handbook of Highway Engineer, Van NostrandReinhold, 1975.
2. Stacy, A.F., “The determination of Pavement Maintenance Strategies” proceedings, Australian Road Research Board, 1978.
3. Asphalt Technology and Construction, Asphalt Institute Park, Maryland, USA, 1978.
4. Local Authority Associations, Highway Maintenance – A Code of Good Practice, Association of County Councils, London, 1989.
5. New Roads and Street Works Act, HMSO, London, 1991.
6. IRC:82-1982 “Code of Practice for Maintenance of Bituminous Surfaces of Highways,” The Indian Roads Congress, New Delhi.
7. Ralph Mass and Ronald Hudson, “Pavement Management Systems” Robert E.Krieger Publishing Company, Florida, 1982.
8. Federal Highway Administration (FHWA), “Construction, Maintenance, Implementation and Management of Highways,” Washington, D.C. 1972.
9. IRC:81-1997, “Tentative Guidelines for strengthening of Flexible Pavements using Benkelman Beam Deflectio Technique,” Indian Roads Congress, New Delhi–1997.
10. Seehra, S.S., “Causes of Failure of the Existing Pavements and their Evaluation for Strengthening.” The Annual Journal of the Institution of Engineers (India), Vol. 11, 1972.
11. Transportation Research Record No. 1597, “Maintenance of Highway Pavements and structures“Transportation Research Board, Washington, D.C.1997.
12. 12. Mookerjee, A.K., “Road Rehabilitation and Maintenance,” International Seminar on Highway Rehabilitation and Maintenance, Organized by Indian Roads Congress, New Delhi, 1999.