Conference Papers

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    SMA mixtures with modified asphalt and treated aggregates
    (American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2014) Goutham, G.; Lekha, B.M.; Monisha, M.; Ravi Shankar, A.U.
    Stone Matrix Asphalt (SMA) is a gap-graded asphalt rich mix with a high concentration of coarse aggregates. In the present investigation, SMA mixtures were prepared with chemically treated aggregates and Crumb Rubber Modified Bitumen (CRMB), and were compared for various characteristics. SMA samples were prepared in conventional Marshall and Superpave Gyratory Compactor (SGC) methods. Volumetric and Marshall properties, Indirect Tensile Strength (ITS), rutting and moisture susceptibility, fatigue behaviour and permeability characteristics were determined for these mixtures. From the laboratory studies it is evident that, chemically treated aggregates with normal bitumen (Viscosity Graded (VG) 30) and CRMB with normal aggregates can be used in SMA to meet the drain down requirements. CRMB mixes were observed to be having an upper hand in performance, even though treated aggregates mixes showed better moisture resistance properties. © 2014 American Society of Civil Engineers.
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    Laboratory Performance of Superpave Mixes for Perpetual Pavements
    (American Society of Civil Engineers (ASCE), 2017) Priyanka, B.A.; Goutham, G.; Lekha, B.M.; Ravi Shankar, A.U.
    Long life asphalt pavement, also known as "Perpetual Pavement", is a pavement with design life more than 50 years and needs only periodic surface renewal. It works on the concept of controlling horizontal tensile strain at the bottom of the asphalt layer and vertical compressive strain at the top of the subgrade to a particular limit. This can be achieved by increasing the binder content of the mix over the optimum binder content (OBC) and by increasing the overall pavement thickness. In the present study two Superpave mixes were prepared using conventional binder at OBC (optimum binder mixture [OBM]) and also at 0.5 % extra binder over OBC (rich binder mixture [RBM]) which can be used in Perpetual Pavements. The mixes were tested for indirect tensile (IDT) strength, moisture susceptibility, fatigue and rutting resistance. From the results it was observed that, OBM performed well as compared to RBM. However the fatigue life of RBM was more compared to the OBM and this helps in reducing the horizontal tensile strain at the bottom of the asphalt layer which in turn increases the life of the pavement. © ASCE.
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    Laboratory Evaluation on the Use of Natural Fibre in Gap-Graded Asphalt Mixtures
    (Springer Science and Business Media Deutschland GmbH, 2023) Chinnabhandar, R.K.; Ravi Shankar, A.U.; Sai Ganesh, V.; Cleetus, A.; Chourasia, S.
    Stone Matrix Asphalt (SMA) is a gap-graded mixture that consists of a high concentration of coarse aggregates, which imparts strength and rut resistance and a high binder content, making the mixture durable. The high binder content mortar consists of fine aggregates, filler, bitumen and stabilising additive. One of the limitations of SMA is it suffers from draindown of binder mortar which can be reduced by adding a mineral fibre, natural fibre or synthetic fibre. The addition of a stabilising additive not only controls the draindown but also improves the tensile strength because of the network of fibres in the mixture. In the present study, an attempt is made to determine the effect of Areca fibre, a natural fibre abundantly available in the southern Indian region. A comparison between two SMA mixtures prepared with and without stabilising additive is made. The Superpave mix design method was adopted, and tests such as draindown, fatigue, rutting and moisture-induced damage properties such as tensile strength ratio (TSR) were evaluated. The results indicate that the mixture with Areca fibre effectively controls the draindown and satisfies the volumetric and mix design criteria as per IRC SP 79. However, the performance of SMA without stabilising additive was better than the mixture with the stabilising additive with respect to resistance to rutting, fatigue and moisture-induced damage. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.