Faculty Publications
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Item Air-cured Alkali activated binders for concrete pavements(Chinese Society of Pavement Engineering, 2015) Palankar, N.; Ravi Shankar, A.U.; Mithun, B.M.The present study focuses on the possibility of use of alkali activatedbinders for use in concrete pavements. Alkali Activated Slag Concrete (AASC) and Alkali Activated Slag Fly ash Concrete (AASFC) are prepared and the properties are compared with Ordinary Portland Cement Concrete (OPCC). The Ground Granulated Blast FurnaceSlag (GGBFS) and Fly Ash (FA) are blended in the ratios 100:0, 75:25, 50:50 and 25:75 as binder and activated using strong alkaline solution. Trial mixes are carried out to identify the optimal Activator Modulus (Ms) for each combination of GGBFS and FA. The mix design for the optimal activator modulus is optimised to achieve sufficient strength for Pavement Quality Concrete (PQC) and the fresh and mechanical properties are studied in detail. The results indicate the properties of AASC and AASFC are similar or slightly better than conventional OPCC and satisfy the minimum strength requirements for concrete pavements. The application of alkali activated binders will minimise the environmental hazards occurring from augmented OPC production, along with effective utilisation of industrial waste materials and conservation of natural resources. © Chinese Society of Pavement Engineering.Item Comparison of Stone Matrix Asphalt mixtures with polymer-modified bitumen and shredded waste plastics(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2016) Goutham, G.; Lekha, B.M.; Krishna, G.; Ravi Shankar, A.U.Stone Matrix Asphalt (SMA) is a gap-graded bituminous mixture characterised with its improved rut resistance and durability. It has comparatively higher proportion of coarse aggregates and binder mastic with bituminous binder and mineral filler. Drain down of mastic content at various stages of construction is a common issue with SMA, and generally, some fibre additives are used to stabilise the mixture or a modified bitumen is used as the binder material. In this study, shredded waste plastics (SWP) are used instead of other stabilising additives, to prepare SMA mixtures with conventional viscosity graded (VG) 30 bitumen. Mixtures were prepared with four different levels of SWP content, and another mixture without any stabilisers was also prepared using polymer-modified bitumen (PMB). Specimens were prepared in superpave gyratory compactor (SGC) for all mixtures at different bitumen contents to determine volumetric and Marshall properties, and optimum bitumen content (OBC) was calculated for each mixture. Tensile strength, moisture susceptibility, rutting resistance and fatigue behaviour were also determined for all mixtures at corresponding OBC. From the available results, the optimum level of SWP in SMA mixture was determined as 8% by weight of bitumen. The study showed that even though mixture with PMB performed the best, SMA with 8% SWP provided comparable results. Based on the present investigation, waste plastic in suitable dosage can be recommended in SMA, instead of a stabilising additive. © 2015 Informa UK Limited, trading as Taylor & Francis Group.Item A study on the effect of rejuvenators in reclaimed asphalt pavement based stone mastic asphalt mixes(Springer, 2019) Durga Prashanth, L.; Palankar, N.; Ravi Shankar, A.U.The present paper focuses on the behavior of Stone Mastic Asphalt (SMA) mixes incorporating rejuvenated Reclaimed Asphalt Pavement (RAP) materials. The RAP materials were tested for its physical properties and later were rejuvenated using various rejuvenators such as waste cooking oil, waste engine oil and shredded plastics. The rejuvenated RAP materials were incorporated in the SMA mixes at various replacement levels i.e. 0%, 30%, 50% and 70% (by weight). Various binder properties such as viscosity, rheological properties and chemical composition were evaluated for the aged and rejuvenated material. The rejuvenators were incorporated at different dosage levels i.e. 2%, 4% and 6% (by weight of binder). The optimal rejuvenation dosage for each type of rejuvenator was identified and mix design for the SMA was optimized for evaluating its physical and mechanical properties. Based on the results, the optimum rejuvenator dosage was identified at 6% for waste cooking oil and waste engine oil, while 2% for shredded plastics. It was observed that the addition of rejuvenators improved the performance of RAP based SMA mixes. © 2019, Chinese Society of Pavement Engineering. Production and hosting by Springer Nature.Item Laboratory Evaluation of SMA Mixtures Made with Polymer-Modified Bitumen and Stabilizing Additives(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2019) Shiva Kumar, G.; Ravi Shankar, A.U.; Ravi Teja, B.V.S.Stone matrix asphalt (SMA) is a gap-graded mixture that consists of two parts, a high concentration coarse aggregate skeleton and a high binder content mortar. The coarse aggregate skeleton provides the mixture with stone-on-stone contact, giving it strength, while the high binder content mortar adds durability. The mortar is typically composed of fine aggregate, mineral filler, asphalt binder, and a stabilizing additive. A stabilizing additive such as natural fibers, mineral fibers, or polymers is added to SMA mixtures to prevent draindown. In addition, it has the potential of reinforcing and improving the tensile strength and cohesion of SMA mixtures. In this study, banana fiber (BF) and pelletized fiber (VP) are used as stabilizing additives to prepare SMA mixtures with conventional viscosity-graded (VG) 30 bitumen. Mixtures were prepared with different levels BF and VP content, and another mixture without any stabilizers was also prepared using polymer-modified bitumen (PMB). Superpave mix design, draindown, fatigue, rutting, workability, and moisture-induced damage properties were evaluated. Results indicated that addition of natural and pelletized fiber controls binder draindown and improves resistance to rutting, fatigue, and moisture-induced damage of SMA mixture. Further, polymer-modified SMA mixtures take less energy for densification compared to SMA mixtures with natural and pelletized fiber. Results also showed that even though polymer-modified SMA mixtures performed better, SMA mixtures with pelletized fiber provided comparable results. © 2019 American Society of Civil Engineers.Item Evaluation of Superpave mixtures for perpetual asphalt pavements(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2019) Priyanka, B.A.; Goutham, G.; Ravi Shankar, A.U.Early deterioration of flexible pavements, due to increased traffic volume, environmental conditions, poor maintenance and construction quality, causes difficulties to road users, all around the world. The structural failures such as fatigue and rutting demand the reconstruction of the pavements which further leads to significant construction cost. One potentially sustainable solution to this problem is to adopt perpetual pavement technology. The fatigue and rutting distresses in the pavements can be minimised to some extent by utilising Superpave mixtures with perpetual pavement concept. This paper proposes two polymer-modified Superpave mixtures, one with optimum amount of binder and the other with rich binder content, for the asphalt intermediate and base layers of perpetual pavement, respectively. The optimum mixtures were prepared with two aggregate gradations having nominal maximum aggregate sizes 25 mm and 19 mm for the intermediate layers to enhance the rutting resistance. Rich mixtures were prepared with the same gradations for the asphalt base layer to improve the fatigue resistance. Laboratory tests were conducted on these mixtures to determine moisture susceptibility, rutting resistance, fatigue behaviour and resilient modulus. The fatigue and rutting criteria of perpetual pavement sections were evaluated using KENPAVE software and the critical strains were found to be within the limits. The experimental results and analysis on perpetual pavement sections with proposed mixtures for the intermediate and base layers show that they can be considered as a better alternative for conventional pavements. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.