Faculty Publications
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Item Evaluation of properties of nonfoaming Warm mix asphalt mixtures at lower working temperatures(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2017) Shiva Kumar, G.; Suresha, S.N.Warm mix asphalt (WMA) is a green technology which has the potential to replace hot mix asphalt (HMA) because it reduces greenhouse gas emissions and energy consumption by lowering the temperature at which asphalt mixtures are produced and placed. During the design process, evaluation of the mix design and mechanical properties of WMA mixtures is necessary. Therefore, the ability to quantify compactability would be very useful. This paper presents details on the evaluation of asphalt mix design, workability, and mechanical properties of asphalt mixtures modified with nonfoaming WMA additives at lower working (mixing and compaction) temperatures. Further, it seeks to provide a wider gap between mixing and compaction temperatures to ensure that WMA mixtures are suitable for longer haul distances. Asphalt mix design properties were evaluated by the Superpave method for various design gyrations (Ndes), and workability properties were evaluated in terms of Superpave gyratory compactor (SGC) densification indices using the Bahia and locking point methods. Mechanical properties such as resistance to moisture-induced damage were evaluated by the tensile strength ratio (TSR) approach, rutting resistance was evaluated by a laboratory wheel tracking test using a wheel rut tester (WRT), and flexural fatigue characteristics were evaluated by four point bending using a repeated load testing (RLT) machine. The effects of nominal maximumaggregate size (NMAS), working temperature, and type of mixture on the properties ofWMAmixtures were investigated. The experimental results were statistically analyzed to identify the major influencing factors and their significance. © 2017 American Society of Civil Engineers.Item Evaluation of workability and mechanical properties of nonfoaming warm mix asphalt mixtures(ASTM International, 2018) Shiva Kumar, G.; Suresha, S.N.Laboratory evaluation of mix design and mechanical properties of Warm Mix Asphalt (WMA) mixtures is necessary during the design process; consequently, the ability to quantify the compactability of WMA mixtures would be very helpful. This article presents the findings of an experimental study aimed at evaluation of the influence of mixing and compaction temperature on mix design and mechanical and workability properties of nonfoaming WMA mixtures. Asphalt mix design properties were evaluated by the Marshall method and the Superpave method. Mechanical properties such as rutting resistance were evaluated by a laboratory wheel tracking test using a Wheel Rut Tester (WRT), and the resistance to moisture-induced damage was evaluated by the Tensile Strength Ratio (TSR) approach. Workability properties were evaluated in terms of Superpave Gyratory Compactor (SGC) densification indexes using the Bahia and locking point methods. Test results indicate that WMA mixtures compacted using SGC at a lower compaction temperature of 110°C, which satisfied the Voids in Total Mixture (VTM) requirement. In order to ensure the Voids in Mineral aggregate (VMA) and Voids Filled with Asphalt (VFA) requirements of WMA mixtures, compaction temperature should be restricted to 120°C. Furthermore, WMA mixtures prepared at lower compaction temperatures exhibited higher resistance to rut deformation because of higher Traffic Densification Index (TDI) values. The energy needed to compact the WMA mixtures at lower compaction temperatures was lower due to lower Compaction Densification Index (CDI) values. WMA mixtures made with surface-saturated dry aggregates and compacted at 110°C marginally fulfilled the minimum TSR requirement because of significant reduction in the Indirect Tensile Strength (ITS) values of conditioned specimen. © © 2018 by ASTM InternationalItem State of the art review on mix design and mechanical properties of warm mix asphalt(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2019) Shiva Kumar, G.; Suresha, S.N.Warm mix asphalt (WMA) is a high-speed emerging technology of producing asphalt mixture at lower temperature with equivalent performance of hot mix asphalt (HMA). It offers benefits such as energy savings, compaction aid for stiffer mixes, reduces emission, and reduces asphalt binder aging during production. This paper is an overview of mix design concept, mix design properties and mechanical properties (moisture-induced damage, rutting resistance and fatigue life) of WMA and same was compared with the properties of control HMA mixtures. Review indicates that mix design concept of WMA is similar to that of control HMA and possesses better mix design properties. Regarding mechanical properties, WMA mixtures were found more prone to moisture-induced damage, rutting and fatigue than control HMA mixtures due to lower production temperature but similar or better resistance were noticed with the use of modified and higher grade binders, addition of anti-stripping agents (ASA) and hydrated lime (HL), use of open graded mix and inclusion of recycled asphalt pavement (RAP). Further, the effect of nominal maximum aggregate size (NMAS) and design gyration (Ndesign) on mix design, NMAS and aggregate type and its water absorption on moisture-induced damage, NMAS, wheel load, test temperature, air voids, and binder grade on rutting, and NMAS, air voids, and stress or strain levels on fatigue properties of asphalt mixtures were analysed. Results indicated that NMAS had the significant effect on moisture-induced damage, rutting resistance and fatigue life of WMA mixtures. WMA mixtures made with aggregates of higher water absorption values were more prone to moisture-induced damage and even fail to meet minimum (tensile strength ratio) TSR requirements. Results also indicated that WMA mixtures made with modified and higher grade binder grade were high rut resistant. WMA mixtures tested at high stress or strain levels shows higher fatigue damage compared to WMA mixtures tested at lower stress or strain levels. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.Item Laboratory evaluation of long-term aging effect on linear viscoelastic and fatigue properties of FAM mixtures(Elsevier Ltd, 2020) Ningappa, A.; Suresha, S.N.Aging is considered as one of the major factor which causes an increase in stiffness and brittleness to asphaltic mixture. This study aimed at evaluating the effect of different aging protocol on viscoelastic and fatigue properties of Fine Aggregate Matrix (FAM) which represents the finer portion (passing 2.36 mm sieve size) of asphalt concrete mixtures. To evaluate the effect of aging on viscoelastic and fatigue properties of FAM mixtures, six different long-term aging levels (6 h at 135 °C, 12 h at 135 °C, 24 h at 135 °C, 5 days at 95 °C, and 12 days at 95 °C aging on FAM loose mixture and 5 days at 85 °C on compacted FAM specimens) were considered. Linear Visco-Elastic (LVE) limit of each FAM mixtures was initially determined by conducting strain sweep test. Viscoelastic properties (|G*| and ?) and master curve shape parameters of FAM mixtures were further determined from temperature and frequency sweep test. Fatigue properties of FAM mixtures at different aging levels were evaluated using strain controlled time sweep test. Irrespective of the aging level applied to the FAM specimen, the LVE limit was found almost constant for all FAM mixtures. Viscoelastic properties (|G*| and ?) for FAM specimen aged for 24 h at 135 °C, and 12 days at 95 °C aged FAM mixtures showed similar results from the master curve plots. The fatigue properties of FAM mixtures decreased as the aging level changed from 5 days at 95 °C to higher level aging of 12 days at 95 °C. Despite of the similar viscoelastic properties, the trend observed between FAM mixtures aged 12 days at 95 °C and 24 h at 135 °C were not found to have similar fatigue properties. Findings of this study on FAM phase can be successfully used to characterize the effect of long-term aging on performance studies of FAM mixtures. © 2020 Elsevier Ltd