Review on the Pavement-repairing Measures as a Condition for the Choice of Road-Maintenance Strategy

The road-maintenance strategies vary from one country to another, and even between the road management authorities within a one single country. It is not surprising, as there is not best maintenance method, nor a universal set of strategies that can be applied equally everywhere. Generally, there are strategies acceptable in certain conditions, but the factors influencing the selection process are diverse and very complex. This paper will present a review of the various measures that can be applied on the roads, which is certainly the basic condition of selection of an appropriate maintenance strategy.


Introduction
The selection of the method of maintenance of the road network in a region or on the whole territory of the country is very complex and intricate.Part of the strategy selection procedure includes the knowledge of the available measures and technologies of pavement maintenance.But, the approach must be a multi-disciplinary one as the selection of the road maintenance strategy is not reduced to the choice of the best maintenance measure, but is the selection of an optimal set of activities in a given time period with the purpose of obtaining an acceptable level of service rendered to the users, but with the lowest possible investments by the state.Some of the factors influencing the application of a certain type of treatments, and thereby the selection of the maintenance strategy include the following: x Previous maintenance; x Available materials; x Access to funds; x Traffic load; x Classification of the roads and the method of their use; x Environmental influence.
Maybe the most important factor is the final effect that a certain treatment will yield onto the pavement in the sense of the pavement behavior and of course, of the users on the short and the long run.The review of the maintenance effects starts with an analysis of the generally accepted measures of pavement repair.They are divided into six categories as follows: x Routine maintenance; x Preventive maintenance; x Thin layers; x Overlay; x Rehabilitations; x Reconstructions.
Each category is organized according to the effect that it is supposed to leave on the pavement and its users, on a design period for which it has been envisaged.The pavement repair measures and a short description of the procedures are given in Table 1.The table offers an overall demonstration of the categories and the maintenance types referring to each category.They are presented hierarchically pursuant to their effect on the overall behavior of the pavement.Of course, there are other maintenance methods, but these procedures are the most frequent and the most widely accepted ones in the world.

Scraping and asphalting in thick layers
Removal of a part of the layer or of one or two layers and their replacement by new ones.

Reconstruction Reconstruction
Removal of the entire asphalt to the lower bearing base and its replacement with new layers.

Routine maintenance
Routine maintenance can be defined as the treatment of the pavement or of the drainage system when it is necessary, to provide for normal functioning of the pavement and of the road in general.Thus, routine maintenance is often referred to as reactive maintenance, meaning that it is performed as a reaction to specific conditions and damages.
Routine maintenance should be continuous, at least when it includes the drainage and the damages signs on the road.An example thereof is the patching, as it cannot be envisaged as a treatment, but is carried out as the pothole appears.
This also includes winter maintenance of the roads, depending on the climate in the country and/or in the region; it must be taken into consideration in order to timely provide the resources for its performance.

Preventive maintenance
Contrary to routine maintenance, in preventive maintenance the treatments are applied before the damages occur.These treatments are meant to prolong the life of the pavement, by restoring or maintaining the desirable characteristics with still economical measures.Maybe the most frequent type of preventive maintenance is the micro-overlay which is applied to protect the pavements against aging and oxidizing.These treatments include application of a thin bitumen layer which is to be absorbed in the surface layer of the pavement.
The preventive maintenance measures are most suitable on pavements which have not yet shown any damage, as is the considerable cracks or disintegration.Most frequently, no aggregate is applied or, if it is, the maximal dimension of the grains is of 10mm.Preventive maintenance is not an efficient method with structure damages, as rutting or crocodile-skin cracks.1.This layers.They can be applied as preventive treatment, but also to restore the skid resistance and the bearing capacity of the pavement.They are also referred to as functional overlay as they are supposed to restore and increase the capacity of the road functioning, but they not increase the bearing features of the construction.The thin layers are usually applied in case of small cracks, small potholes and minimal rutting.Larger rutting can be treated by filling or in combination with thin surface treatment.2. Overlay.Overlays primary purpose is to increase the bearing features of the construction.Considerable improvement of the bearing capacity is achieved when the overlay is more than 40mm thick.It is applied in initiation of structural deformations of the pavement (rutting, potholes, crocodile-skin cracks) or in case of increased traffic load which has not been envisaged by the pavement design.It is carried out with an asphalt layer which is also used in constructing of new roads.The best results are achieved by first repairing the existing road and then applying the new asphalt layer.3. Rehabilitation.Rehabilitation is a large modification of the pavement construction.Unlike the overlay, rehabilitation always includes interventions on one or more asphalt layers.They include scraping, which removes the surface layer and often goes deeper than one layer, with new or recycled material.Rehabilitation is the most effective measure on pavements where signs of structural damage have occurred (most frequently crocodile-skin cracks or rutting), but not to the degree that would require complete reconstruction.4. Reconstruction.Reconstruction implies removal and replacement of asphalt layers to the sub-base and/or replacement of the blanket course to the grade.Upon partial reconstructions some parts of the original construction are left unchanged.Complete reconstruction consists of removal of all included materials, grade treatment and building of a new construction.Reconstruction is justified when the pavement is destroyed, and the grade requires enforcement (including drainage).5. Other treatments.There is other maintenance treatment, but it is not easy to classify them.For example, simple scraping without the application of an asphalt layer or emulsion is also performed to decrease the rutting level or increase friction.If it can be proved that there will be no more rutting, than such a measure is justifiable.If rutting is expected again, this measure is considered as temporary.Recycling is often related to rehabilitation.In fact, it can be part of any maintenance strategy, as many bitumen types and aggregates can be reused if treated properly.Recycling is an efficient strategy if the materials are in good shape and if the procedure is economical.

Maintenance effects
The application of a certain maintenance treatment should be considered immediately after the decision to intervene, before the occurrence of new deformations under the influence of the new traffic load and under the influence of the climate factors.In certain cases all the damages will thus be eliminated, or some of them will be eliminated partially, depending on the treatment applied.The following Tables (2 to 7) give the relation of individual maintenance treatments and their effects on different types of deformations.5 gives the percentages of decrease of change coefficient depending on the intensity of damage for the different layers of the pavement construction.Table 8.Suggested values of reduction of the change coefficients a i depending on the pavement condition.The change of the structural number of the construction with time is the basic condition in the selection of the technology that shall be applied upon the pavement repair.

Conclusion
The introduction of a road network management system is a precondition for the adoption of a road strategy.Only with detailed knowledge of the road network, its damages, the needs of maintenance and the available technologies, it is possible to initiate the adoption of a strategy of maintenance, of course, considering the available financial resources.Here, special emphasis should be laid on the analyses of different maintenance scenarios, whereby it is necessary to analyze the funds necessary for each of them, and then adopt the most favorable one considering the available finances, and to establish the future maintenance strategy.The application of this kind of method in planning and programming of the maintenance will contribute to the definition of a strategy of maintenance, by which would provide for the most optimal use of the financial resources in order to provide for the maximal improvement of the economic life of the pavements of the country's road network.

Table 2 .
Influence of certain treatments on the pavement's crack level.

Table 3 .
Influence of certain maintenance treatments on ravelling. 2023Table