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This paper presents the development of a laboratory testing procedure for the evaluation of flexible pavement crack routing and sealing techniques. The testing procedure simulates both sealant installation techniques and environmental and traffic conditions. An experimental program involving the affecting factors has been designed and is represented in the paper. For the covering abstract of this conference, see IRRD number 863140.
This study used over forty-four lane miles of test site to gather up to three years of comparative performance data on thirteen crack sealants. The data indicates that the more durable, high ductility materials when applied in a band-aid configuration can be expected to give significantly better performance than the lower ductility materials used by the Utah DOT prior to 1983. Evaluation of sealant placement procedures indicates that routing is a questionable practice, and that the hot compressed air lance may significantly improve the performance of materials placed during cold or wet conditions. Evaluation of UDOT maintenance activities indicates that sealant melters cannot achieve or maintain the required sealant application temperatures under colder winter conditions. The efficiency of melter units should be improved or not operated under those conditions. More accurate temperature gauges on melter units should be acquired. Inaccurate gauges may cause impaired sealant performance and safety.
A survey of all 50 United States was conducted in September of 1990 to determine the state of the art of crack sealing procedures on flexible asphalt concrete pavements. The results were tabulated and a summary report prepared. A meeting was held at the U.S. Army Cold Regions Research and Engineering Laboratory to discuss the draft report; the comments and suggestions received were incorporated into this report. At the meeting the group identified the need for a trade organization to develop uniform specifications and terminology and to promote proper equipment, methodology, materials, training and education in the pavement crack sealing industry.
The primary purpose of this study was to develop criteria to improve the effectiveness of Utah's flexible pavement crack sealing practice. The methodology involved field measurements of seasonal variation in crack width and in-depth interviews of Department members at various levels of management in maintenance, materials, construction, and research. Other states were queried by questionnaire in order to obtain a comparative base on with to evaluate Utah's practice. Findings indicate that flexible pavement cracking is a significant problem in the Far West, Rocky Mountains, Great Lakes, and New England. Criteria to determine when to seal (fill) cracks, and materials or techniques to be used vary widely. Choice of materials if affected by storage requirements and equipment available. Prepackaging of materials especially designed for crack sealing has resulted in improvements in control of mix and material properties; further gains can be anticipated as mix design improves and material specifications become more exact.. Low temperature and freeze thaw cycles significantly affect the amount of thermal cracking and the performance of crack sealant. Poor rideability, increased pavement deterioration, obscured traffic markings, lowered skid resistance can result from inappropriate selection and installation of crack sealants. Ductile sealants such as Crumb rubber/asphalt cement mixes, in combination with routing appear to offer substantial gains in sealant life and performance. These gains are partially offset by increased installation cost and hazard to the operator. Existing data is insufficient for benefit/cost analysis.
Crack sealing and filling are two of the main traditional techniques of asphalt pavement preventive maintenance. However, these techniques have the shortcomings of low operating efficiency and poor performance such as secondary cracking and edge failure. In this paper, the investigation results of field performance of crack seal band are presented. The seal band is a promising material of crack repair because it results in fewer secondary cracks and greater operating efficiency (two to four times more efficient than crack sealing). However, the field investigation also revealed four major failure modes of seal band, namely, unevenness, cohesion failure, adhesion failure, and pullout that provide the demand to carry out laboratory studies on the properties of seal band material. The following standards are referenced in the studies: (1) standard of hot-applied sealant, (2) standard of building waterproof roll, and (3) standards of related enterprises. Six evaluating test methods are put forward based on the laboratory studies, including: thickness meterage, width meterage, cone penetration test, softening point test, pullout test, and bond test. Fifteen seal band samples are tested in a laboratory evaluation. Based on the field investigation and test results, the technical requirements of different seal bands used in different areas are proposed.
Crack sealing is a practice used for routine and preventive maintenance as part of a pavement's preservation strategy. However, crack sealant failures are common in Texas, particularly within the first 3 years of application (or service life). The major causes of sealant failures can be classified under two categories: Adhesion failure and cohesion failure. Although both failures can lead to a significant reduction in the service life of a pavement structure, adhesive failure is in most cases the dominant failure type. Several laboratory tests such as rotational viscosity, penetration, softening point, ductility, and bond tests are currently used to evaluate the properties of crack sealants. Among these tests, the bond test is specifically used to evaluate the adhesive failure of crack sealants and the procedure of the bond test is well documented in ASTM D5329-07. However, the bond test often takes several days to complete, and the pass/fail criterion is determined through visual observation, which is a very subjective process. Furthermore, the correlation between the bond test and adhesive failure performance of crack sealants in the field was found to be either weak or non-existent. In an attempt to minimize these problems, a simple, fast, and adhesive performance-related laboratory test method is developed in this paper to ensure the proper selection of a sealant for a given project.