Maintenance engineers have been applying treatments to both flexible and rigid pavements ever since there have been these types of pavements. The types and application of various treatments for both corrective and preventive maintenance have been the subject of research studies over a number of years, and many publications have reported these findings. FHWA recently initiated an effort to encourage departments of transportation at all levels to begin, or extend, the practice of preventive maintenance, since there simply is not enough money available to continue the types of maintenance currently employed. Flexible pavement preventive maintenance is specifically addressed, including the types of pavements that are candidates for preventive maintenance, the available treatments, where and when they should be used, their cost-effectiveness, factors to be considered in selecting the appropriate treatment strategy, and a methodology to determine the most effective treatment for a particular distress.

Preventive maintenance techniques are considered useful in extending the life of a pavement if applied at the right time. Discussed here is a framework for a process that can be used to select the proper maintenance strategies for different distress types in asphalt pavements, depending on traffic level and environment. Maintenance treatments addressed include only crack seals, fog seals, slurry seals, microsurfacings, chip seals, thin asphalt concrete overlays, and other thin surface treatments. Types of distress considered include roughness, rutting, fatigue cracking, longitudinal cracking, raveling, weathering, and bleeding. Decision trees, based on the authors' experiences, are presented to illustrate the process in selecting appropriate maintenance treatments. A framework for evaluating the cost-effectiveness of the various maintenance treatments is presented. Existing methods for evaluating cost-effectiveness of maintenance are discussed together with their strengths and weaknesses. An example of cost-effectiveness for different maintenance treatments is also briefly presented.

No abstract

A variety of materials have been used for wearing surfaces on steel bridge decks. The requirements for these paving materials are identified, the various asphalt-based materials that have been used are described, a description of the construction process is provided, and the expected field performance and maintenance requirements for the most common materials used are discussed. The selection of the wearing surface should be based on life-cycle costs, not just initial construction costs. Life-cycle-cost calculations must include consideration of initial construction costs, expected life, maintenance and rehabilitation costs, and user delay costs associated with the removal and replacement of failed surfaces. The reliability, durability, and skid resistance of the wearing surface are very important to prolongation of the life of the surfacing and minimization of delays to users caused by frequent replacements.

One of the major difficulties in asphalt concrete pavement construction is the control of materials and the subsequent level of payment to contractors for materials not conforming to specifications. The effect of this noncompliance on pavement serviceability is not fully established; however, it frequently results in reduced payments to contractors, which, in turn, causes much controversy between the two parties. Specific mixture properties outside specification tolerance, which are accepted by most agencies through reduced payment include percent compaction, asphalt content, and mix gradation. The reduced payment used normally relies heavily on the experience and judgment of the agencies; therefore, there is often wide disparity in the pay adjustment factors used. The paper summarizes currently available techniques for estimating the modulus and fatigue life of asphalt mixtures and shows how these, together with existing failure criteria for fatigue and permanent deformation may be used to estimate the effects of changes in compaction on pavement life. Secondly, the results of extensive laboratory tests on asphalt mixtures from three projects in Oregon are reported. Tests were performed to evaluate the effect of mix variations (including density) on mix properties (modulus, fatigue life, and resistance to permanent deformation). Tests were run using both as-compacted and conditioned (vacuum saturated followed by freezing then heat soaking) specimens. The test used throughout was the ASTM Repeated Load Diametral Test (D 4123-82) modified slightly such that fatigue life could be evaluated. The results of the test program indicated that percent compaction (or void content) was the most significant factor affecting mix performance. An increase in void content is associated with a decrease in modulus, fatigue life, and resistance to permanent deformation. The result of the study findings was the development of new asphalt concrete compaction specifications for the state of Oregon. Not only does the Oregon Department of Transportation (DOT) now require a higher standard of compaction (91% of American Association of State Highway and Transportation Officials [AASHTO] T209 maximum specific gravity), but they have also spelled out clearly the penalties for not achieving density.