Compaction at the Longitudinal Construction Joint in Asphalt Pavements (KYSPR-00-208)

Poor compaction practices at longitudinal construction joints in hot-mix asphalt (HMA) pavements lead to premature pavement failure. The hypothesis is that poorly constructed or compacted HMA joints tend to be more permeable and allow water to enter into the pavement structure, accelerating pavement deterioration processes. In recent years, it has become evident how critical proper longitudinal joint construction is to the life of the pavement structure. Recent water and icing problems on US 460 and US 23 in Pike County, premature pavement failures on I-75 in Scott County, and other problems found throughout the state indicate that construction joints may be allowing water to rapidly enter the pavement structure. The water appears to be causing several problems such as debonding of surface layers, mixture stripping, aging of the asphalt (oxidizing and hardening), and other associated problems, all of which accelerate pavement failure. Many pavements have been, or are in the process of being, resurfaced as a direct or indirect result of longitudinal joint deterioration. The objectives of this study were to evaluate the level of compaction at the construction joint in HMA pavements on new and existing projects; to determine the level of water infiltration and segregation at the joint and its effect on joint performance; to determine the most promising joint construction methods around the nation and worldwide by reviewing specifications, experiences, and construction practices for joint construction and the prevention of joint segregation; to develop specifications and construction methods to ensure the level of density necessary at the joint for proper performance; and to review special paving equipment (attachments) for improving the densification of the unsupported edge. Four methods of joint construction were evaluated in this study. These were the notched wedge (12:1), restrained edge, joint reheater, and Joint Maker. In addition, a number of joint adhesives were used. Some of the major conclusions and recommendations from the study include: • Contractors are consistently achieving levels of density at or near the construction joint that are within three percent of the lane density. It is recommended that specifications be written that would require contractors to achieve that level of density at or near the construction joint. • The reheater achieved the highest joint density of all the methods; however, only one short project was included in the study. The effects of reheating the mat could not be determined during construction, but will be evaluated during long-term monitoring. The restrainededge method of joint construction achieved the second highest overall densities and statistically was significantly better than the conventional method of construction. The notched wedge only marginally improved densities overall, while the Joint Maker showed no improvement over conventional construction techniques. It is recommended that more projects be constructed using the restrained-edge method. • It appeared the notched-wedge method produced the lowest permeabilities at the joint. • Preliminary performance data indicate that all projects are currently performing well with projects having joint adhesives performing as well as, or better than, projects without joint adhesives. It is recommended that other projects be constructed using joint adhesives. 1 1.0 INTRODUCTION Poor compaction practices at longitudinal construction joints in hot-mix asphalt (HMA) pavements can lead to premature pavement failure. The hypothesis is that poorly constructed or compacted HMA joints tend to be more permeable and allow water to enter into the pavement structure, accelerating pavement deterioration processes. In recent years, it has become evident how critical proper longitudinal joint construction is to the life of the pavement structure. Recent water and icing problems on US 460 (Figure 1) and US 23 in Pike County, premature pavement failures on I-75 in Scott County (Figure 2), and other problems found throughout the state (Figure 3) indicate that construction joints may be allowing water to rapidly enter the pavement structure. The water appears to be causing several problems such as debonding of surface layers, mixture stripping, aging of the asphalt (oxidizing and hardening), and other associated problems, all of which accelerate pavement failure. Many pavements have been, or are in the process of being, resurfaced as a direct or indirect result of longitudinal joint deterioration. The objectives of this study were to evaluate the level of compaction at the construction joint in HMA pavements on new and existing projects; to determine the level of water infiltration and segregation at the joint and its effect on joint performance; and to determine the most promising joint construction methods around the nation and worldwide by reviewing specifications, experiences, and construction practices for joint construction and the prevention of joint segregation. These reviews included Kentucky, other states, countries, and agencies that are involved in joint construction. Additional objectives were to develop specifications and construction methods to ensure the level of density necessary at the joint for proper performance; and to review special paving equipment (attachments) for improving the densification of the unsupported edge. 2.0 A REVIEW OF NATIONAL EXPERIENCE WITH EXPERIMENTAL LONGITUDINAL CONSTRUCTION JOINTS A detailed literature review and phone survey of users and manufacturers of joint-construction equipment were conducted to determine the most promising construction methods to improve longitudinal construction joints in Kentucky. From this literature review and survey, three primary methods were chosen. These methods were the notched-wedge joint, restrained edge, and Joint Maker. Other methods were later added to this research effort which were showing promising results for other state departments of transportation (DOTs). These methods included reheating the cold joint and adhering the joint between adjoining lanes together with a joint adhesive (either a mastic joint tape or a hot extruded adhesive). The cutting wheel method was considered but was not tested because of questionable feasibility of statewide implementation. Extensive joint research has been conducted by the National Center for Asphalt Technology (NCAT) and several participating DOTs. In 1992, NCAT conducted a joint study evaluating seven construction techniques in Michigan and eight in Wisconsin (NCAT Report No. 94-1). The techniques utilized and density results obtained are shown in Table 1. Of the techniques tried in Michigan, the two wedge joints gave the highest density at the joint, followed by the cutting wheel. In the Wisconsin test sections, the restrained edge had the highest density at the joint and the cutting wheel had the second highest density.