Maryam S. Sakhaeifar

Trackless tacks are used to minimize the loss of tack materials caused by adherence to moving tires. During the last two decades, the paving industry and highway agencies have had an increasing interest in the use of trackless tacks to ensure an adequate bond between the overlay and the existing pavement. Therefore, the need for more studies on the bonding characteristics of various trackless tacks is growing. The purpose of this study is to measure the bonding potential of trackless tacks and identify several variables that affect the shear resistance in terms of bonding strength and energy using statistical analysis. The improvement of interlayer shear resistance by tack treatment is different depending on the tack and surface types. Higher tack reactivation temperatures increase the interlayer shear resistance. Compaction effort is considered to have only a marginal effect on bond performance. Tack and surface types play a more critical role in determining the shear bond strength than residual tack rate in the field experiment.

Rehabilitating and preserving the current pavement networks have become top priorities for many highway agencies. The structural overlay is one type of rehabilitation solution widely used to improve the structural capacity of pavements. Selecting the proper overlay mixture with the desired performance plays a significant role in extending the service life of an existing pavement. This study focuses on evaluating the performance of overlay mixtures commonly used in rehabilitation projects in Oklahoma. The overlay performance was assessed by integrating laboratory tests with field distress surveys. Five mixtures varying in binder content, nominal maximum aggregate size, and reclaimed asphalt pavement content were identified. Laboratory performance of these mixtures was determined through conducting dynamic modulus tests, direct tension cyclic fatigue tests, Hamburg wheel tracking tests, and indirect tension creep and strength tests. The effect of mixture variables on stiffness and performance was investigated, and resistance of mixtures to fatigue cracking, thermal cracking, and rutting was evaluated. Also, the correlation between five different types of performance test results was investigated. It is recognized that Hamburg and direct tension cyclic fatigue test results are highly correlated, and the mixtures with less permanent deformation under cyclic loading are less susceptible to fatigue cracking. Also, a strong correlation between dynamic modulus and direct tension fatigue test results was found. The laboratory-estimated performance of the selected mixtures was then compared with observations from field distress over a period of time after placement of overlays. A few representative flexible pavement sections in the Oklahoma highway network rehabilitated with these overlay mixtures were identified, and their distress data were monitored. It was observed that field performance data are in a good agreement with laboratory evaluations, and the ranking of mixtures for cracking and rutting susceptibility captured in the laboratory correlates well with observations from the field. At the end of this study, a decision table is suggested for the use of laboratory tests in the selection of appropriate overlay mixtures. The decision tree is developed to prioritize the use of performance tests based on the condition of existing pavements and correlation between the performance test results.

Proactive pavement preservation applies low-cost treatments frequently to mitigate deterioration, whereas the traditional approach to preservation is reactive to distresses, requiring intensive rehabilitation or reconstruction. Airfield pavement preservation requires adequate planning in order to efficiently mitigate pavement deterioration. Large airports generally have dedicated staff and specified budget for the management and maintenance of their pavement network; however, these resources may be lacking in many general aviation (GA) airports in the United States. Therefore, technical rules for pavement preservation should be documented and simplified for GA managers to inhibit quick deterioration and address proactive preservation. In this paper, a database and the development of guidelines for the selection of long-lasting and cost-effective treatments are introduced. A tool has been designed especially for nontechnical decision makers in GA. The developed guidelines cover both asphalt and concrete pavements, but this paper focuses on flexible pavements only. Selected treatments vary depending on different climate zones and airport traffic and service, which is reflected in airport categorization. Furthermore, the selection of an optimal treatment based on benefit-to-cost-ratio analysis is discussed.

The selection of long-lasting and cost-effective rehabilitation strategies is crucial to pavement engineers. Development of rehabilitation and preservation decision trees and support tools that involve performance scores are pursued by agencies across the world. However, for the purpose of rehabilitation selection, pavement scores determined from pavement-distress surveys reveal flaws in capturing pavement needs. This paper introduces a rehabilitation methodology based on the application of a damage ratio estimated from falling-weight deflectometer (FWD) data, and a rutting index determined from a distress survey. A detailed project-level investigation was conducted on a series of flexible and composite (asphalt over an existing portland cement concrete layer) pavement sections from a high-traffic-volume interstate highway network. The study includes the evaluation of existing pavements through back-calculation of FWD data and monitoring field-distress data, conducting asphalt mixture laboratory testing as well as mechanistic–empirical pavement design guide and life cycle cost analysis. The results of analyses are used to develop a robust methodology and a series of time-based rehabilitation strategies for a network of flexible and composite pavement sections located in Oklahoma.

In recent years, the quieter pavement surface which can affect traffic noise levels has been needed largely due to increasing public awareness and demand. The objective of this research is to utilise two methods of measuring tyre–pavement interaction noise and to investigate the influence of different pavement characteristics on tyre–pavement noise level. The first method used the close-proximity noise trailer and the second method used on-board sound intensity measurement. The pavement characteristics considered are pavement texture and smoothness, air voids, pavement stiffness, and nominal maximum aggregate size (NMAS) of asphalt mixtures. The tyre–pavement noise was measured by different techniques from various types of pavement sections in the National Center for Asphalt Technology test track. Testing was conducted on four major family groups of Superpave fine and coarse graded, open-graded friction course, and stone matrix asphalt mixes from 2009 Test Track research cycle to evaluate the changes over time. Relative significance analysis is performed to detect the combined effect of pavement texture and smoothness, air voids, pavement stiffness, and NMAS on tyre–road noise levels. The results show that the noise levels vary widely according to pavement surface type. The evaluation confirms that macrotexture increases the low-frequency noise and higher air void content reduces the high-frequency noise level, while other surface characteristics were found to have less influence on noise levels. The content of this study can be used in the vehicle and pavement noise development process to decrease the tyre–pavement interaction noise and for pavement design and construction to determine appropriate quieter pavement surfaces.

Tracking of traditional tack coat materials is a common concern during hot-mix asphalt overlay construction. This problem can be avoided by using trackless tacks, which are recently developed tack products that resist sticking to tires. Thus loss of tack materials from the paving surface is preventable. Various trackless tack products have been introduced to the market; however, there is still a lack of evaluation on their tracking resistance. The objective of this study was to measure the rheological and tack properties of trackless tack materials through the dynamic shear rheometer. Six trackless tacks and a traditional tack were evaluated. To identify rheological characteristics, the dynamic shear rheometer frequency sweep test was performed on the tack residues. Also, the modified dynamic shear rheometer tackiness test was conducted on both tack emulsions and residue at different temperatures. The emulsion samples were tested throughout the curing period. The tack samples were categorized into soft and stiff binder groups with respect to complex shear modulus obtained from the frequency sweep test. The tack energy was estimated to quantify the stickiness in the tackiness test. A significant difference in tack energy was observed between soft and stiff group binders. The stiffness of the investigated tack materials with respect to the complex shear modulus is well correlated with the tack material properties.

Non-tracking tacks are introduced to improve the bonding of pavement layers by preventing the tracking problems associated with conventional tacks. However, the evaluation of the non-tracking tacks has not been well-established as compared with the traditional tack coats. The goal of this research was to measure the rheological properties, the bonding potentials and tack properties of non-tracking tack materials. For this purpose, the dynamic shear rheometer (DSR) frequency sweep test was performed on the tack residues for investigating their rheological properties. Also, a pneumatic adhesion tester was used to measure the pull-off strength of the interaction between the residues and aggregate. The DSR tackiness test was conducted to identify the tracking resistance and quantify the tack energy. Three non-tracking tack coats and a traditional tack coat were used. The results of the DSR frequency sweep test showed that the non-tracking tack materials are stiffer than the traditional tack coat. The results from the pull-off testing and the DSR tackiness test demonstrated that the effect of tack type on the bond strength and tackiness was significant. Furthermore, it was shown in the tackiness test that the testing temperature had a major impact on the change of tack energy for the non-tracking tacks.

Adequate planning for airfield pavement preservation is required for efficient mitigation of pavement deterioration due to loading and environmental conditions. Large airports generally have trained staff for managing their pavement network and a significant budget for routine maintenance. However, there are many general aviation (GA) airports in the U.S. which may lack these resources. Therefore, technical rules for pavement preservation need to be simplified for GA airport managers. While the typical approach to managing these pavements is reactive, which requires costly rehabilitation/reconstruction, proactive preservation uses more frequent, low-cost treatments. In this paper, a tool for the selection of durable and cost-effective treatments for pavement preservation, and steps and database used for development of this tool are introduced. This tool can be used by non-technical decision makers in general aviation. The results for selection of treatments vary depending on different climate zones and airport traffic reflected on airport categories.

Non-tracking tacks, recently introduced to the paving industry, bond pavement layers while avoiding the tracking problems associated with traditional tacks. Initially, there was only one supplier of non-tracking tack in Texas, but now multiple producers are bringing products to the market. Performance to date has been good, but there are no established methods to test tackiness/tracking resistance of current and new products. The objective of this research, therefore, was to develop and assess three tests for measuring tracking resistance: the modified no-pick-up time test, the TTI sand adhesion test, and the modified DSR tackiness test. These methods were evaluated on four tack materials, three curing temperatures, and at 10-minute curing time intervals. The results from the modified no-pick-up time test were clearly influenced by curing time and curing temperature. The TTI sand adhesion test could discern among different tack materials. Track free time may be defined as less than 2 g of sand adhesion. The modified DSR tackiness test showed measurable differences among the tack types and different temperatures and times. Of these test methods, the researchers recommend adoption of the modified no-pick-up time test for routine tracking resistance testing. “Track-free time” should be defined as less than 10% tracking in 40°C curing. Testing of this and other tests should continue, especially with other conventional and non-tracking tacks.