Faculty Publications
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Item Utilization of Ferrochrome and Recycled Concrete Aggregates for Sustainable Pavement Base Layers—A Laboratory Study(Springer Science and Business Media Deutschland GmbH, 2025) Chiranjeevi, K.; Kumar, D.H.; Yatish, R.G.; Talkeri, H.T.; Mulangi, R.H.; Ravi Shankar, A.U.The paramount importance of incorporating alternative aggregates cannot be overstated, as it plays a pivotal role in resource conservation, sustainability promotion, and efficient waste management. This study focuses on the utilization of ferrochrome aggregate (FCA) and recycled concrete aggregate (RCA) within cement-treated base layers, aiming to entirely substitute natural coarse aggregate (NCA). The research meticulously fabricated cement-treated recycled and ferrochrome aggregate (CTRFA) samples with cement contents of 3, 5, and 7%. These specimens incorporated varying blends of RCA and FCA, ranging from 0 to 100%. In this investigation, strength properties such as unconfined compressive strength (UCS), flexural strength, elastic modulus, and indirect tensile strength (ITS) were performed alongside durability. The experimental results indicated that the cement content exerted a more pronounced influence on both strength and durability. The CTRFA mixes containing 50% RCA, 50% FCA, and 5% cement meet IRC 37 2018 strength and durability standards and can be used as a base layer for flexible pavement instead of conventional cement-treated base (CTB). © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.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 Optimization and Characterization of Ferrochrome and Recycled Concrete Aggregate Mixes for Pavement Base Layers(American Society of Civil Engineers (ASCE), 2025) Chiranjeevi, K.; Kumar, D.H.; Yatish, R.G.; Mulangi, R.H.; Ravi Shankar, A.U.Utilizing alternate aggregates is crucial for conserving resources, promoting sustainability, and managing waste effectively. The focus of the current study was the utilization of ferrochrome aggregate (FCA) and recycled concrete aggregate (RCA) in cement-treated base layers with the objective of entirely replacing natural coarse aggregate (NCA). The study meticulously prepared cement treated recycled and ferrochrome aggregate (CTRFA) specimens with 3%, 5%, and 7% cement content. These specimens incorporated varying blends of RCA and FCA, ranging from 0% to 100%. Response surface method (RSM) was used to optimize the mixes by considering strength and durability criteria for cement treated bases (CTB). Microstructural characterization was aimed to explore aggregate surface roughness, mortar hardness, mineral phases, cracks, and elements within the matrix. The outcomes of optimization revealed that the optimal mixture, meeting the specifications of the Indian Road Congress, could be achieved by substituting 61% RCA and 39% FCA with 4.8% cement content. © 2024 American Society of Civil Engineers.Item Preliminary evaluation of treated bio-residue as a modifier for bitumen(Elsevier B.V., 2025) Yatish, R.G.; Chiranjeevi, K.; Kumar, D.H.; Raviraj, H.M.; Ravi Shankar, A.U.R.With the global shift toward sustainable construction practices, the reuse of organic industrial by-products in pavement applications is gaining momentum. Bio-residues, when appropriately treated, can serve as eco-friendly alternatives to conventional binders. This study presents a preliminary investigation into the use of thermally treated Caffeine Spent Residue (CSR) as a partial replacement for bitumen in binder formulations. The CSR, derived from organic industrial waste, underwent thermal pretreatment to improve compatibility with the bituminous phase. The treated CSR was then mixed with bitumen (VG-40) by replacing it at varying levels—0 %, 3 %, 6 %, 9 %, 12 %, and 15 % by weight using a laboratory-scale high-shear mixer to produce Bio-residue Modified Bitumen (BRMB). The resulting BRMB samples were evaluated through penetration and softening point tests, along with rheological characterization using the Superpave rutting parameter (G?/sin ?) to assess the influence of treated CSR on fundamental binder properties. Both unaged and RTFO-aged samples were analyzed to capture the impact of short-term ageing on consistency and rutting resistance. Additionally, a cradle-to-gate assessment of embodied energy (EE) and embodied carbon (EC) revealed that replacing 10 % of bitumen with treated CSR significantly reduced the energy consumption and carbon emissions per kilogram of binder. The findings establish that treated CSR, particularly at a 9–10 % replacement level, offers a promising pathway for enhancing the sustainability of bituminous binders. © 2025 Elsevier B.V.Item Comparative Analysis of 85th Percentile Operating Speeds for Different Vehicle Categories Under Daytime and Nighttime Conditions: A preliminary Investigation(Nigerian Institution of Professional Engineers and Scientists, 2025) Sanganaikar, R.S.; Mulangi, R.H.; Yatish, R.G.Understanding spatiotemporal variations in vehicle operating speeds is essential for improving road safety on rural highways, particularly under low visibility nighttime conditions. This study investigates 85th percentile operating speeds (V85) of three vehicle categories, motorized two wheelers (MTWs), passenger cars (CARs), and heavy commercial vehicles (HCVs) at five key points along 30 horizontal curves on a two-lane rural highway in Karnataka, India. Spot speed data, collected using laser speed cameras under free flow conditions, were statistically validated and analysed across both daytime and nighttime. Results reveal consistent speed reductions at night, with CARs showing the highest nighttime deceleration, particularly at curve midpoints, while MTWs maintained moderate speeds across lighting conditions. Paired t-tests, Wilcoxon signed rank tests, ANOVA, and post hoc Tukey analyses confirmed significant inter vehicle and inter segment speed variability. The segment from point of curvature (PC) to midpoint (MC) emerged as the most critical for all vehicle types and conditions based on composite variability rankings. These findings underscore the need for targeted countermeasures such as enhanced mid curve delineation, vehicle specific entry warnings, and improved nighttime visibility, tailored to segment and vehicle class. The study offers a replicable framework for prioritizing design and safety interventions and highlights the value of integrating statistical diagnostics and composite ranking approaches in rural highway safety assessments. © 2025 NIPES Pub. All rights reserved.