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 Utilization of Recycled Concrete Aggregates Processed Using the Ball Milling Method in Cement-Treated Bases for Pavements(Springer Science and Business Media Deutschland GmbH, 2024) Chiranjeevi, K.; Kumar, D.H.; Kumar, A.J.; Thapas, N.D.S.; Ravi Shankar, A.U.Pavement construction and maintenance have become very common worldwide as traffic volumes and vehicular axle weights continue to rise as the global population grows and technology advances. The extensive utilization of natural resources implies that their existence for long-term availability cannot be assured. Using materials from the various damaged and collapsed structures will save money and find a solution to the trash disposal issue. These materials have inferior engineering properties compared to conventional materials and cannot be used directly in pavement applications. These materials must be processed or stabilized by mechanical and chemical stabilization techniques. Processing of Recycled Concrete Aggregates (RCAs) has gained more importance in improving the physical properties. In the current investigation, construction and demolition (C&D) waste was processed in two stages successively. In the first stage, C&D waste was subjected to manual crushing and further processed through jaw crushing. The aggregates were processed through ball milling in the second stage. The natural aggregates are entirely replaced with the RCA in cement-treated bases (CTBs) at 3, 5, and 7% stabilization levels. Mechanical and durability properties were evaluated. The RCA produced from the ball milling method performs better than the unprocessed RCA. The mix having 7% cement content with processed RCA met the specifications for CTB. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.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 Optimisation of recycled concrete aggregates for cement-treated bases by response surface method(Taylor and Francis Ltd., 2023) Chiranjeevi, K.; Kumar, D.H.; Srinivasa, A.S.; Ravi Shankar, A.U.Sustainability is a primary concern that needs to be addressed since infrastructure development requires significant natural resources. Using Recycled Concrete Aggregates (RCA) for road construction has numerous benefits in saving natural resources and the environment. In the present investigation, the demolition waste is being used for road construction, partially/fully replacing natural aggregates. The Cement Treated Recycled Concrete Aggregate (CTRCA) specimens were prepared at 3%, 5%, and 7% cement with various blends of RCA and Natural Coarse Aggregates (NCA) ranging from 0 to 100%. The strength characteristics in terms of Unconfined Compressive Strength (UCS), Flexural Strength (FS), Elastic Modulus, Indirect Tensile Strength (ITS) and durability tests were conducted on cured samples. Microstructural analysis using Scanning Electronic Microscope (SEM) revealed that the pores and cracks in the old mortar have a detrimental influence on the mechanical properties of CTRCA mixes. However, Energy Dispersive Spectroscopy (EDS) and durability tests have shown positive results. The Response Surface Method (RSM) was utilised to optimise the RCA and cement content in CTRCA mixes. The research resulted in the maximum possible RCA of up to 70% with a cement content of 5.8%, which met the Indian Road Congress (IRC) specifications for Cement Treated Bases (CTB). © 2023 Informa UK Limited, trading as Taylor & Francis Group.Item Utilization of recycled concrete aggregates for pavement base courses – A detailed laboratory study(Elsevier Ltd, 2024) Chiranjeevi, K.; R G, Y.; Kumar, D.H.; Mulangi, R.H.; Ravi Shankar, A.U.R.Pavement construction and maintenance have become prevalent globally due to increasing traffic volumes and higher vehicular axle weights, driven by population growth and technological advancements. However, the extensive reliance on natural resources raises concerns about their long-term availability and sustainability. An emerging trend in construction involves the application of alternative materials, such as demolished waste and industrial by-products, as substitutes for natural materials like aggregates. This study examined strength properties, including unconfined compressive strength (UCS), flexural strength, elastic modulus, indirect tensile strength (ITS) and the performance aspects of durability, shrinkage, and fatigue. Cement stabilized recycled concrete aggregate (CSRCA) mixes were prepared by varying the percentage of natural coarse aggregate (NCA) and recycled concrete aggregate (RCA) from 0% to 100% and cement content from 3% to 7%. The experimental findings demonstrated that the cement content had a more significant impact on the strength and performance characteristics of CSRCA mixes than RCA content. The mixes with RCA replacement up to 50% and a cement content of 5% satisfy the strength and durability criteria recommended by IRC 37. A higher proportion of RCA was found to have a detrimental effect on mechanical properties and fatigue characteristics. It was found that the CSRCA mixes with 50% RCA replacement to NCA can be used as a base layer instead of a conventional cement-treated base (CTB) for flexible pavement. © 2023 Elsevier Ltd