A pavement performance and life-cycle cost evaluation of a polymer modified asphalt cement Styrelf) has shown technical advantages and cost savings. The evaluation involved seven Ontario asphalt concrete pavements, representing various traffic and climatic conditions, placed between 1987 and 1992. A surface distress survey was completed for representative sections with the polymer modified asphalt cement and control sections with conventional asphalt cement. Rut depth was determined from transverse profiles. The surface distress information was analyzed using the American Public Works Association PAVER procedures to determine the Pavement Condition Index for each section. This information was used to model the pavement condition through a 30 year analysis period. Life-cycle costing was completed to determine the present worth of the construction, maintenance and rehabilitation costs. The pavement performance modelling indicated the polymer modified asphalt cement extended the pavement service life by about 4 to 6 years compared to conventional asphalt cement. This service life extension was confirmed by testing representative asphalt concrete cores in the Nottingham Asphalt Tester, which indicated improved rutting resistance and increased fatigue life. The results of the life-cycle cost analysis showed significant life-cycle cost savings for pavements incorporating polymer modified asphalt cement mixes. For the covering abstract of this conference see IRRD number 872978.

This synthesis will be of interest to pavement designers, maintenance engineers, and other concerned with selection of pavement designs and pavement rehabilitation alternatives. Information is presented on how life-cycle can be used to select the alternative that is least expensive over time.

This Interim Technical Bulletin recommends procedures for conducting Life-Cycle Cost Analysis (LCCA) of pavements, provides detailed procedures to determine work zone user costs, and introduces a probabilistic approach to account for the uncertainty associated with LCCA inputs.

Polymer-modified binders (PMB) have been shown over the decades to improve the mechanical properties of asphalt mixtures compared to unmodified binders. Considering the higher initial cost of PMB, selecting the best alternative is very important, especially for local agencies given their limited budgets. A challenge in the materials selection process for low-volume roads is the limited information available, which could allow engineers to determine whether using PMB is cost-effective. In this research, we investigate the use of PG 58H-34 PMB binders (grade C) and PG58S-28 unmodified binders (grade B) for low-volume roads in Minnesota. Historical pavement performance data are analyzed to compare the field performance of modified and unmodified mixtures. Laboratory experiments are performed to compare the low-temperature cracking properties of polymer-modified and unmodified binders and mixtures commonly used in Minnesota. Based on the experimental results, a life-cycle cost analysis (LCCA) is performed comparing the use of polymer-modified and unmodified binders for low-volume roads in Minnesota. The results show that using PMBs for new construction is expected to extend the pavement service life by 6 years, and that using PMB is more cost-effective than using unmodified binders for low-traffic roads.

In 2014, researchers at the Virginia Transportation Research Council initiated a study to evaluate the effectiveness of using high polymer-modified (HP) binders in surface asphalt concrete (AC) mixtures. The results were promising enough to support a field study investigating the use of HP binders in asphalt mixtures over jointed concrete pavement. Since 2015, HP AC overlays have been placed at several sections over existing jointed concrete pavement and cracked asphalt pavements in an effort to mitigate reflective cracking. The purpose of this study was to assess the viability of using HP AC mixtures in Virginia as a reflective crack mitigation technique or when deemed appropriate as a tool for increased crack resistance on higher volume facilities. Information on the state of the practice and lessons learned from the use of HP AC mixtures in the United States and Canada are also provided. In general, HP AC mixtures have been used in a wide range of applications under heavy traffic on interstates and slow-braking loads at intersections. No major field-related construction issues in terms of mixing temperatures and in-place compaction of HP AC mixtures were reported and standard construction practices and equipment were used. Good communication between the polymer/binder supplier and the contractor and solid planning prior to the work being conducted were important lessons learned with regard to paving with HP AC mixtures. The performance characteristics of conventional polymer-modified asphalt (PMA) and HP field-produced mixtures were evaluated in the laboratory in terms of durability and resistance to rutting and cracking. Based on the mixtures tested in this study, HP AC mixtures showed better performance when compared with PMA mixtures regardless of the mixture type (dense-graded surface mixtures and stone matrix asphalt [SMA]). Moreover, SMA mixtures showed better performance when compared with surface mixtures regardless of the asphalt binder type (PMA and HP). Overall, SMA-HP mixtures showed the most promising performance among all evaluated PMA and HP mixtures. Distress survey data collected from VDOT’s Pavement Management System of HP field sections were compiled, documented, and compared with that of their control PMA sections. The HP sections showed the most promising performance 5 years after construction (2015-2020) regardless of the traffic level and the pre-existing pavement conditions. In general, none of the evaluated mixtures (HP or PMA) was able to stop reflective cracking totally. Moreover, performance evaluations using the network-level pavement management data were conducted to estimate the life expectancy of HP AC overlays. Overall, PMA and HP AC overlays had an average predicted service life of 6.2 and 8.3 years, respectively, indicating a 34% extension of performance life of the AC overlays with HP modification. The study recommends continued assessment of the as-constructed properties in future HP projects for the purpose of compiling a materials characterization database. Further, the performance of all existing and future HP sections should be monitored. This will help in updating and revising the service life prediction models and the cost-effectiveness of using HP AC mixtures as the existing sections continue to age and more data are available. Finally, the use of the balanced mix design approach should be investigated to promote further the design of more durable and longer-lasting PMA and HP mixtures in Virginia.