Conference Papers
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Item Stone matrix asphalt using aggregates modified with waste plastics(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2014) Goutham, G.; Lekha, B.M.; Ravi Shankar, A.U.R.Stone matrix asphalt (SMA) is a gap-graded asphalt mixture performing better than conventional dense-graded mixtures. It contains a high concentration of coarse aggregates (forming stone-on-stone contact between them) and high asphalt content. The coarse aggregate skeleton results in better load distribution and the high asphalt content adds durability to the mixture. Due to the high mastic (filler and asphalt) content, there is possibility of drain down during various stages in construction. SMA mix should be prepared with a suitable stabilizing additive to prevent the drain down of mastic material from the mixture. In this study, SMA mixtures are prepared in a Super pave Gyratory Compactor (SGC) with shredded waste plastics, which are mixed with aggregates prior to the addition of Viscosity Graded (VG) - 30 asphalt. Mixtures are prepared with asphalt contents of 5.0 to 7.0 per cent (by weight of aggregates) and stabilizer contents of 0, 4, 8, 12 and 16 per cent (by weight of asphalt). Volumetric and Marshall properties, tensile strength, and moisture susceptibility characteristics are determined. From the laboratory studies, it is observed that addition of waste plastics in shredded form can be used instead of stabilizers by controlling the drain down and enhancing the performance. © 2014 American Society of Civil Engineers.Item 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.Item 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.Item Investigation on the Effect of Anti Stripping Additives on the Moisture Sensitivity of Bituminous Concrete(Springer Science and Business Media B.V., 2018) Ravi Shankar, A.U.; Goutham, G.; Lekha, B.M.; Carlton-Carew, C.Moisture damage is one of the most common reasons for the premature deterioration of Hot Mix Asphalt (HMA) pavements. Over the years, extensive research has been carried out by scientists and engineers on this subject; however, pavements still succumb to early failure from infiltrating moisture. A very popular method of minimizing the moisture susceptibility of asphalt pavements is by the use of anti-stripping agents. These additives are chemical substances that alter the physicochemical properties of the asphalt by making it more hydrophobic. This study focuses on the effect of anti-stripping agents on the moisture susceptibility of Bituminous Concrete (BC) mixture. The anti-stripping agents used were hydrated lime and Zycosoil. Three mix types were studied, namely: BC mix without additive, BC mix with hydrated lime and BC mix with Zycosoil. Viscosity Grade (VG) 30 bitumen was used in all three groups of samples. Marshall mix design method was adopted and specimens were prepared at bitumen contents 4.5, 5.0, 5.5, 6.0, 6.5 and 7.0% by weight of mixture. Volumetric properties and Marshall characteristics were determined for each specimen, and using them, the Optimum Binder Content for each mixture was obtained. Moisture susceptibility of mixtures was assessed using Tensile Strength Ratio, Retained Stability and Stripping Value. From the experimental results, it is observed that the addition of anti-stripping agents had a significant positive influence on the results of the test properties being evaluated in each test. © 2018, Springer International Publishing AG.