Faculty Publications
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Item Fatigue and Engineering Properties of Chemically Stabilized Soil for Pavements(Springer, 2013) Lekha, B.M.; Ravi Shankar, A.U.; Goutham, G.Soil stabilization is a technique to improve the weak soils and making them to meet certain requirements of the specific engineering projects. The type of soils available in Dakshina Kannada region of Karnataka State is laterite and Lithomarge clay. Its Plasticity Index is very high due to the presence of high percentage of silt and clay content. In the present investigation, an attempt is made to study the behaviour of laterite with and without adding chemicals. A chemical named Zycosoil, when added to water and mixed with soil alters its engineering properties that depend upon the type of the soil and dosage of chemical. These chemicals are liquid additives, which act on the soil to reduce the voids between soil particles and minimize adsorbed water in the soil for maximum compaction. In the present study, the effectiveness of Zycosoil in stabilizing the laterite soils of South Canara district is investigated through laboratory experiments. Various geotechnical properties are studied and correlations between different geotechnical properties and improvement in the soil properties with different percentages of chemical additions are derived. The important properties such as index properties, compaction characteristics, unconfined compressive strength parameters, California bearing ratio values and fatigue behaviour were studied. The results obtained indicate that there is an improvement in almost all properties with the addition of Zycosoil. © 2012 Indian Geotechnical Society.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 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 Stabilisation of lithomargic clay using alkali activated fly ash and ground granulated blast furnace slag(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2020) Amulya, A.; Ravi Shankar, A.U.; Praveen, M.A suitable ground improvement technique is essential in order to confront the problems associated with lithomargic clay for road construction. The efficacy of alkaline solutions such as sodium hydroxide and sodium silicate along with class F fly ash and Ground Granulated Blast Furnace Slag (GGBS) as additives to improve the properties of lithomargic clay is examined. The different mixes are prepared by replacing the soil with 20%, 30%, and 40% of GGBS and fly ash. The Maximum Dry Density (MDD) obtained from the soil replaced with 40% GGBS and for the soil replaced with 30% fly ash. An activator modulus of 1.25 is kept constant for the varying sodium oxide dosage at 2, 3 and 4 per cent. The Unconfined Compressive Strength (UCS) of the alkali-activated soil cured for 3, 7 and 28 days is determined and compared with the UCS of the soil replaced with fly ash and GGBS at both standard and modified proctor densities. The different mixes are tested for the durability, California Bearing Ratio (CBR). The soil is replaced with GGBS and fly ash does not pass the durability test while the alkali-activated mixes with 4% sodium oxide dosage is found to be durable. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.Item Laboratory evaluation of use of areca fibres in SMA mixes(Taylor and Francis Ltd., 2023) Chinnabhandar, R.K.; Kumar, H.K.; Yatish, R.G.; Ravi Shankar, A.U.One of the problems associated with Stone Matrix Asphalt (SMA) mixes is the drain down of binder mortar during production, transportation and placement of the mixes. A commonly adopted method to control the drain down is to add a stabilising additive such as natural, synthetic or mineral fibres to the mixture, which is also known to improve the mechanical and volumetric properties of SMA. The present study evaluates the feasibility of using areca fibres extracted from areca husk in SMA as a stabilising additive. Three SMA mixtures were prepared with Viscosity Grade VG 30 bitumen using areca fibre (SMA-AF), coconut fibre (SMA-CF) and cellulose fibre in pelletised form (SMA-PF) and their performance was compared with a control SMA mixture prepared using Polymer Modified Bitumen (SMA-PMB). The prepared SMA specimens were evaluated for volumetric and Marshall properties, workability characteristics, Indirect Tensile Strength (ITS), fatigue, rutting and moisture susceptibility. The drain down test results indicated that the fibres controlled the drain down, and the optimum fibre content was 0.3% for the mixes with fibres. All the mixtures satisfied the requirements of SMA per IRC:SP 79-2008. The statistical analysis conducted revealed that the fibre type had a significant effect on the properties of SMA mixes. The SMA-PMB and SMA-CF mixes required the least and the highest energy for compaction. Among the mixes with natural fibres, SMA-AF performed better than SMA-CF. © 2022 Informa UK Limited, trading as Taylor & Francis Group.