Maryam Sakhaeifar

Evaluation of Long-Lasting Perpetual Asphalt Pavement with Life-Cycle Cost Analysis

In 2006, the Oklahoma Department of Transportation sponsored work at the pavement test track of the National Center for Asphalt Technology to compare the performance of two sections that had been designed to determine the necessary thickness for perpetual pavement. One section (Section N9) was designed to be a perpetual pavement at 14 in. thick. The other section (Section N8), at 10 in. thick (according to the AASHTO 1993 design guide), was used to test performance and to identify the thickness needed for perpetual pavement. This paper presents a life-cycle cost analysis for quantifying the benefits of a perpetual pavement section compared with the long-term cost of the thinner section. The life-cycle cost analysis was conducted with RealCost 2.5, which was available through FHWA, and included a determination of quantitative estimates of construction schedule, work zone user costs, and agency costs for initial construction and rehabilitation activities. The perpetual pavement section was found to have had a lower life-cycle cost than the conventional pavement section and to have provided better service to highway users. For better planning of future preservation studies, the estimated present serviceability rating as a function of the international roughness index for two designs (perpetual and nonperpetual) was evaluated. The findings of surface measurements for both sections demonstrate a clear difference between perpetual and conventional pavement serviceability for a given level of roughness and accumulated traffic. These results are also useful for assessing the improvement of conventional pavement after rehabilitation treatments.

Mechanistic-empirical methodology for the selection of cost-effective rehabilitation strategy for flexible pavements

Abstract A well-planned rehabilitation approach helps agencies to optimise the allocation of annual investment in pavement rehabilitation programs. Currently, many agencies are struggling with the selection of an optimal time-based and cost-effective rehabilitation solution to address the long-term needs of pavements. This study offers the use of a mechanistic-empirical methodology to develop a series of time-based rehabilitation strategies for high traffic volume flexible pavements located in Oklahoma. Six different pavement family groups are identified in the state, and comprehensive evaluation of existing pavements are conducted through analysis of falling weight deflectometer data and performance measures available in Oklahoma Pavement Management System database. The inadequacy of performance measures to fully characterise the condition of existing pavements are indicated, and damage factor determined from FWD data are suggested as trigger factor to select rehabilitation candidates. Three levels of rehabilitation activities including light, medium and heavy are considered as potential alternatives for rehabilitation candidates. A mechanistic-empirical methodology is employed to obtain an estimate of the performance of rehabilitation and extension in service lives of pavements. Also, an assessment output matrix is developed, which can be served as a supplemental tool to help the decision-makers in the highway agency with the rehabilitation related decision-making process. Cost-effectiveness of rehabilitation alternatives is determined through life cycle cost analysis, and three time-based renewal solutions are developed for pavement family groups that are in need of rehabilitation.

Selection of Structural Overlays Using Asphalt Mixture Performance

AbstractRehabilitating 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 t...

Decision-making Tool for the Selection of Pavement Preservation Treatments in General Aviation Airport Pavements

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 United States (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.

Tyre–pavement interaction noise levels related to pavement surface characteristics

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.

Evaluating Tack Properties of Trackless Tack Coats Through Dynamic Shear Rheometer

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.

Development of Rehabilitation Strategies Based on Structural Capacity for Composite and Flexible Pavements

AbstractThe selection of long-lasting and cost-effective rehabilitation strategies is crucial to pavement engineers. Development of rehabilitation and preservation decision trees and support tools ...

Chemical-Mechanical Interaction of Non-Tracking Tack Coat and Aggregate on Bond Strength

The effectiveness of a hot-mix asphalt (HMA) overlay is largely dependent on the quality of its bond to the existing surface. A good bond will evenly disperse traffic loads from one layer into the next, while a poor bond will concentrate stresses within relatively thin upper layer. This condition will expedite premature distresses like fatigue cracking, slippage cracking and delamination. All of these problems are then exacerbated by moisture accumulating at the bonded interface. Non-tracking tacks, recently introduced to the paving industry, bond asphalt layers together while avoiding the tracking problems under traffic associated with traditional tacks. While traditional tack has been well studied, these new products require further evaluation. Of particular concern is the loss of adhesion between exposed aggregate on the existing road and asphalt binder. The objectives of this study were to characterize existing non-tracking products, and measure the bonding potential of different types of aggregate from a chemo-mechanical perspective. For this purpose, the rheological properties of the emulsion residues and base binder of five non-tracking tacks and one conventional tack were characterized. The bonding potential between the tack and different aggregate substrates was measured with a pneumatic adhesion tester. The results show significant differences in bond strength of aggregates with rough surface and the control binder or emulsion residue at different testing temperatures. The control binder and emulsion residue at different testing temperatures were also found to develop different bond strength with any given aggregate. The results show that the control binder and emulsion residue have different degrees of sensitivity to aggregate type in terms of their bond strength.

Development of Test Procedures to Measure Tracking Resistance of Non-Tracking Tack Coat

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 Texas Transportation Institute (TTI) sand adhesion test, and the modified dynamic shear rheometer (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.

Tackiness Properties of Non-Tracking Tack Coats

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.