Faculty Publications
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Item Alkali Activated Black Cotton Soil with Partial Replacement of Class F Fly Ash and Areca Nut Fiber Reinforcement(Springer Science and Business Media Deutschland GmbH, 2023) Chethan, B.A.; Ravi Shankar, A.U.; Chinnabhandar, R.K.; Kumar, D.H.Alkali activation has received great attention for improving the soil properties with suitable precursor materials. Industrial byproduct class F fly ash was suitably utilized to improve Black Cotton (BC) soil properties along with ordinary Portland cement by various researchers. However, the CO2 emission associated with cement production has enforced the evaluation of alternative binders. Laboratory investigations were conducted on BC soil by admixing various fly ash dosages (0–50%) and reinforcing the mix with 0.5% areca nut fiber. Alkali activator solution prepared using 8 molar sodium hydroxide solution (SH) and sodium silicate solution (SS) at 1.5 SS/SH ratio showed significant improvement in Unconfined Compressive Strength (UCS) of stabilized BC soil on 7 and 28 days curing. The reinforcement was effective in improving the flexural strength of stabilized mixes. Exorbitant unsoaked California Bearing Ratio (CBR) values were observed on 28 days of curing. However, the samples could retain low soaked CBR values despite reinforcement. Scanning Electron Microscope (SEM) images showed the reduction of shrinkage cracks and strong bonding of fibers in the stabilized mix. X-Ray Diffraction (XRD) patterns evidenced the formation of various hydration products due to the alkali reaction, which resulted in the high strength gain of mixes at ambient temperature curing. The leaching of mineral constituents from the set mix lead to the failure of durability samples. Due to nondurability, the alkali activation with a selected precursor cannot suit pavement materials requirements. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item 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.Item Unmodified Bitumen in SMA: A Sustainable and Cost-Effective Approach(Springer Science and Business Media Deutschland GmbH, 2025) Arun, U.; Chinnabhandar, R.K.; Talkeri, H.T.; Yatish, R.G.; Ravishankar, A.U.Stone Matrix Asphalt (SMA) is a Hot Mix Asphalt (HMA) mixture consisting of a discontinuous aggregate gradation characterised by a high coarse aggregate content (between 70 and 80%), a high percentage of binder (typically between 6 and 7%) and a filler content as high as about 10%. SMA has an aggregate skeleton which imparts high strength and rutting resistance to the mixture. The high binder content though provides the mixture with durability, it also drains through the void spaces in the aggregate skeleton during production, transportation and placement of the mixture in the field. Hence, to reduce the drainage of bitumen and bitumen mortar, the SMA guidelines suggest using a modified bitumen or pelletised cellulose fibres in the mixture when a conventional bitumen such as Viscosity Graded (VG 30) is used. However, the production of cellulose fibres is not only expensive but also requires trees to be cut since cellulose is obtained from plant sources leading to deforestation. Due to the high cost of Polymer Modified Bitumen (PMB), the SMA mixtures prepared with the modified bitumen are also expensive. Hence, the present study focuses on the laboratory evaluation of SMA mixes using a conventional Viscosity Graded bitumen (VG 40) without the use of pelletised cellulose fibres. The results indicated that the susceptibility of mixtures to drainage of binder and/or binder mortar was within the permissible limit of 0.3% by weight of the mixture. The mechanical and moisture susceptibility tests conducted on compacted specimens indicated that the performance is comparable to that of the mixtures prepared using PMB. Further, it was noted that only the grades of bitumen softer than VG 40 required cellulose fibres to reduce drain-down. The study also revealed a reduction in cost due to not using cellulose fibres with VG 40 bitumen or modified bitumen, which makes it more environmentally friendly and sustainable. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item A review of the potential application of lignin in the production of bio-binder: challenges and opportunities(Springer, 2024) Yatish, R.G.; Kumar, D.H.; Chinnabhandar, R.K.; Raviraj, H.M.; Ravi Shankar, A.U.R.The aim is to treat nature in such a way that usage of natural resources has little to zero hazards to our environment. There is a need to protect the earth and its ecology from approaching disasters brought on by anthropogenic activity, particularly the combustion of fossil fuels for energy. The net-zero emission shall be achieved worldwide by embracing sustainable bio-energy resources. Under this domain, the invention of bio-ethanol also known as 2G-ethanol from crop residue (lignocellulosic biomass) took place and is contributing toward rural development and energy independence. Similarly, researchers have modified the conventional petroleum-based bitumen by incorporating various types of lignin, including wood lignin, kraft lignin, soda lignin, lignosulfonates, and lignin-derived from biofuel production. This review encompasses the growth in biofuel production and advantages stemming from bitumen modified using lignin obtained as a byproduct from bio-fuel industries. The study also explores potential approaches for producing a direct alternative bio-binder using lignin. However, there remains a necessity for dedicated research and development to optimize the production methods of bio-binders. Using bio-bitumen or bio-binder in constructing bituminous layers shall contribute to reducing the dependency on fossil fuels, lowering the carbon footprint, improving the performance, and valorizing the biowaste. This review comprehensively outlines the challenges in the production of bio-binder from lignin. Also, this shall serve as a starting point for further research projects by highlighting the potential of lignin as a source for developing a direct alternative bio-binder in pavement engineering. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.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.Item Effect of aggregate gradation and bitumen type on mechanical properties of semi-flexible asphalt mixtures(Elsevier Ltd, 2023) Kumar, D.H.; Chinnabhandar, R.K.; Chiranjeevi, K.; Ravi Shankar, A.U.R.Semi-Flexible Asphalt (SFA) mixture is a wearing course in which Open-Graded Asphalt (OGA) mixes having air voids of 20–35% are grouted with cement mortar. The grout consists of cement, sand, superplasticizer, and water. In the present work, an effort was made to assess the effect of the Sand-Cement (S/C) ratio in determining the optimal grout proportions. Taguchi technique combined with Grey Relational Analysis was used to obtain the optimal grout proportion. The optimum grout was found to be the mixture prepared with an S/C ratio of 0.6, a water-to-cement (W/C) ratio of 0.40, and a polycarboxylic ether-based superplasticizer (SP) content of 0.75% by weight of cement. The SP content was the most influencing factor, while the S/C ratio was the second most influencing factor. To investigate the effect of aggregate gradation and bitumen type on the mechanical properties of SFA mixtures, a new aggregate gradation with neat and modified bitumen was used to prepare OGA mixtures and later grouted with optimal grout proportion. The Marshall Stability, compressive strength, Indirect Tensile Strength, Cantabro loss, fatigue resistance, moisture and Oil spillage resistance tests were conducted. The results showed that the SFA mixtures prepared with polymer-modified bitumen and the new aggregate gradation have better mechanical properties, implying the significance of bitumen type and aggregate gradation. © 2023