This synthesis report will be of special interest to pavement designers, materials engineers, and others seeking information on portland cement concrete resurfacings (overlays) placed over both portland and asphalt cement concrete pavements. Information is presented on the various practices in use for the design, material selection, and construction techniques associated with each pavement type. Additional information is provided on resurfacing experience and performance, including an Appendix cataloging more than 700 existing resurfacing projects in North America. Transportation agencies in the United States are continuing to develop pavement management systems which take an objective and structured approach to life-cycle cost analysis requirements for pavement rehabilitation project analysis. This report of the Transportation Research Board also discusses the considerations involved in the selection of technically feasible resurfacing alternatives. Based on the longitudinal experience of 375 resurfacing projects that were cataloged in 1982 and the more than 700 projects identified in 1993, much useful information on the performance characteristics of portland cement concrete resurfacing is presented.

Fabric reinforcement was used in an attempt to prevent reflection cracking of two bituminous concrete layers overlying an 8-inch plain (unreinforced, unjointed) concrete base that was underlain by a portland cement stabilized subbase material. On these pavements it was expected that the extremely rigid base and subbase layers would reduce vertical motion to a minimum. Similar pavements constructed with no overlay reinforcement readily showed reflection cracking in the bituminous layers, presumably because of horizontal, thermally induced movements of shrinkage cracks in the concrete base.

At head of title: National Cooperative Highway Research Program.

This synthesis report will be of special interest to pavement engineers and pavement construction and maintenance personnel responsible for portland cement concrete (PCC) pavement joints. Still pertinent information from NCHRP Synthesis 19 (1973), as well as new or updated information in the areas of joint design, construction, and maintenance are included. This report of the Transportation Research Board records the state of the practice with respect to the design, construction, and maintenance of PCC pavement joints. In addition, information on joint materials and sealing, the control of water on and in pavements, and the evaluation of pavement joint performance is provided.

This report summarizes the activities undertaken to implement a pavement management system at 56 general aviation airports coming under the jurisdiction of the Virginia Department of Aviation (VDOAV). The system, which is called Micro-PAVER, is a proprietary program developed by the U.S. Army Corps of Engineers. It is reported to be used at many airports in the U.S. and abroad and by many local government agencies in the U.S. Implementation involved the training and the use of highway employees as airport inspectors, the development of an historical data base for each airport, cataloging the current condition of each runway pavement, and the development and inclusion of feasible maintenance policies and their estimated costs in a computer package. Finally, a series of condition and projected future condition reports as well as reports concerning the estimated rehabilitation costs were developed from the computer package for each airport. The project covered a period of approximately 18 months and utilized nearly 50 VDOT employees. Several recommendations to the VDOAV concerning the future of general aviation airport pavement management are included.

The report describes the Virginia Department of Transportations' first modern experience with the construction of thin-bonded Portland cement concrete overlays of existing concrete pavements and with the fast track mode of rigid paving. The study was conducted in cooperation with the Federal Highway Administration (FHWA) and used a paving mixture verified in an FHWA mobile laboratory. The study showed that the fast track mode will permit lane closure times as short as 48 hours. Of special interest was the finding that adequate strength of the bond between the old pavement and the overlay is not dependent on the use of a bonding grout.

Studies of efforts in Virginia to reduce the incidence of reflection cracking when portland cement concrete pavements or bases are overlayed with asphaltic concrete are reported. The methods of reflection crack reduction discussed are: (1) The use of sand as a bond breaker between portland cement concrete pavements and asphaltic overlays, (2) the use of a high tensile strength fabric as a stress relieving layer between two asphaltic concrete overlays of an old portland cement concrete pavement on a weak subbase, and (3) the use of two types of fabric as stress relieving layers between asphaltic layers and a concrete base on a very strong subbase and subgrade. The following conclusions were drawn. 1. Neither sand as a bond breaker nor high strength fabrics as stress relieving layers are effective in reducing reflection cracking where vertical joint movement (differential deflection) is a significant factor. 2. When differential deflections are greater than about 0.002 in (0.05 mm) reflection cracks form early. Such cracking is delayed for lower differential deflection but may occur as the magnitude and frequency of wheel loadings increase. 3. Both an asphalt impregnated polypropylene fabric and an unwoven, spun-bonded nylon fabric, when placed to span joints in portland cement concrete base and covered with an asphaltic concrete, overlay, are able to sustain the formation of reflection cracking in the overlaying layer without undergoing damage. 4. An asphalt impregnated polypropylene fabric spanning the joints in portland cement concrete pavements, and placed between the pavement and an asphaltic overlay, may be effective in reducing the infiltration of surface water to pavement sub-layers. There is some evidence that pavement pumping may be reduced by this method. 5. Both an asphalt impregnated polypropylene fabric and an unwoven, spun-bonded nylon fabric can delay the formation of reflection cracking. There is strong evidence, however, that such cracking is fatigue in nature and will eventually develop under the application of repetitive wheel loadings.

The construction and performance of seven Virginia flexible pavements containing at least some experimental features were evaluated. The objective was to evaluate the performance of the pavements incorporating new or timely design concepts and to assess the flexibility of these concepts for further use.

An evaluation was made of the applicability of the geophysical technique of radar subsurface profiling to estimating the extent of sidewalk undermining. It was found that there is a distinct difference between the observed radar echo patterns of a nonundermined sidewalk and those from an undermined sidewalk. Therefore, it is feasible to determine from the radar scan of a sidewalk the length of the sidewalk that is undermined. It is also feasible to determine the approximate depth of voids underneath an undermined sidewalk; however, this may sometimes be difficult to achieve. The approximate cost of surveying a sidewalk with the technique was also estimated.

A study of the KJ. Law Model 8300 Roughness Surveyor was begun in 1985 to determine the feasibility of replacing Mays Meter roughness testing equipment with an easier to use and more repeatable alternative. The original schedule called for completion of the study in late 1986. However, the study was badly delayed because of equipment failures, long delays by the manufacturer when the equipment was returned for trouble shooting, and altered priorities placed on the research staff: Because of these altered priorities, the study was tabled for several years so that final testing was not completed until mid-1991. It was found that, with certain limitations, the Surveyor (sn 1372) is capable of correlation with other roughness testing equipment and of providing test results meeting the requirements ofHPMS Class II equipment. Among the major limitations are the following: (1) on coarse-textured surfaces, the device is highly sensitive to variations in testing speed, and (2) the device is highly sensitive to changes in ambient temperature. The author concludes that these limitations are too severe for the device to be used in any except very uncritical roughness testing.