Faculty Publications
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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 Laboratory investigation on cement-treated recycled concrete aggregate bases for flexible pavements(Elsevier Ltd, 2023) Chiranjeevi, K.; Hemanth Kumar, D.; Yathish, R.G.; Ravi Shankar, A.U.India's economy is progressing fast, and many infrastructure development programs are going on. Especially the road network expansion is going on many folds. As a result, natural coarse aggregates are getting depleted, which has an impact on environmental sustainability. Utilizing the resources from the many aged and demolished structures will be cost-effective and solve the disposal problem of these wastes. India's government insists on using marginal material, demolished waste, or recycled aggregates as alternative materials for road construction. New codes developed by IRC and MoRTH recommend Cement Treated Bases (CTB) and Cement Treated Sub-Bases for pavement lower layers. In light of this, the present study attempts to utilize Recycled Concrete Aggregates (RCA) obtained from construction and demolition (C&D) waste in the CTB. The efficiency of RCA was checked at various replacement levels ranging from 0% to 100% with cement stabilization of 3%, 5%, and 7%. The strength properties like Unconfined Compressive Strength (UCS), Flexural Strength and durability were evaluated. The microstructural characteristics and elemental analysis of the cement treated recycled concrete aggregate mixtures were examined. The research yielded the highest potential RCA of up to 50% with a cement content of 5%, meeting the Indian Road Congress (IRC) criteria for CTB. © 2023Item 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 LtdItem 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 Optimizing Ball Milling for High-Quality Recycled Aggregates: Examining the Mechanical Processing and Performance of Cement-Treated Bases(American Society of Civil Engineers (ASCE), 2025) Chiranjeevi, K.; Ramagiri Girish, Y.; Hemanth Kumar, D.; Mulangi, R.H.; Ravi Shankar, A.U.Producing superior-quality recycled aggregates from demolition waste is challenging. Over the years, mec hanical treatment methods for removing attached mortar from aggregates have evolved significantly. The studies on effective recycled coarse aggregate (RCA) processing with optimized processing parameters using ball milling and characterization of processed RCA (RCA) are limited. In this study, central composite design in the response surface method was employed to optimize control process factors (charge, revolution time, and aggregate weight) with aggregate properties as responses (percentage mortar removal, water absorption WA, specific gravity Sg, impact value IV, and abrasion value AV). The aggregate processed with optimized processing parameters exhibited superior quality with enhanced physical properties. The effect of the processing of RCA on the mechanical properties of cement-treated bases was studied by utilizing processed RCA in cement-treated recycled concrete aggregate mixes. The microstructural analysis was performed using 3D-surface topography, scanning electron microscopy, and energy dispersive spectroscopy. The test results demonstrated a 63% reduction in water absorption and an improvement in Sg, IV, and AV by 12.3%, 38%, and 23.7%, respectively. It is also found that the unconfined compressive strength and flexural strength with processed RCA are improved by 31.5% and 45.7%, respectively. Natural coarse aggregate can be completely replaced with processed RCA in cement-treated bases with the optimized processing method. © 2025 American Society of Civil Engineers.