BITS Faculty Publications

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Author: search.filters.author.Pradhan, SubhasisSubject: search.filters.subject.Civil engineering

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    Particle packing method for recycled aggregate concrete
    (Springer, 2024) Pradhan, Subhasis; Barai, Sudhir Kumar
    This book highlights the use of commercially available recycled aggregate concrete (RAC) extracted from multiple construction and demolition sites, considering it as a viable alternative to conventional aggregate. It further describes the advanced techniques, such as, scanning electron microscopy, nanoindentation, thermogravimetric analysis and X-ray microtomography shedding light on the deep-rooted causes of inferior macro-mechanical performance of RAC and the advantages of particle packing method design approach in this regard. It then describes the improved properties of RAC with the help of macro-mechanical performance studies, microstructural characterization and fracture analysis. The systematic and in-depth presentation of the use of recycled coarse aggregate as an alternative to conventional aggregate for the preparation of structural concrete will guide researchers on subsequent research in RAC and provide assistance to structural engineers and concrete manufacturers for the usage of RAC.
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    Reaction kinetics and thermodynamic modeling of alkali-activated calcined marine clay with mechanical activation
    (Elsevier, 2025-09) Pradhan, Subhasis
    A clinker-free, one-part alkali-activated materials (AAM) using calcined marine clay (CMC) and Ca(OH)2 (CH) was developed in this study. The influence of mechanical activation on the mechanical properties, morphology, and the microstructure of one-part AAM was explored. Chemical dissolution test elucidates the relationship between reacted SiO2/Al2O3 content, CH content, and pH values throughout the reaction process. Leveraging these experimental and statistical analysis results, a novel quantitative study on the kinetics of alkali activation process and the impact of milling on one-part AAM was conducted through thermodynamic modeling. CH dissolution-controlled reaction kinetics was revealed through experimental and modeling equilibrium comparisons. It demonstrates that the co-milling of CMC and CH can facilitate the alkali activation by synergistically improving the reacted CaO, SiO2, and Al2O3 content via accelerated dissolution of CH and CMC. This research advances understanding for one-part AAM design by optimization of precursor/activator content and mechanical activation time via experimental and modeling approaches
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    Synergistic effect of particle packing method, aggregate saturation levels, and paste content in improving the performance of high volume fine recycled aggregate concrete
    (Springer Nature, 2025) Pradhan, Subhasis
    Using fine recycled concrete aggregate (FRCA) is challenging because of the presence of mortar fines in higher quantities. Past studies have reported a few approaches (Presoaking FRCA, surface treatment of FRCA, use of mineral admixture, method of mix proportioning, and mixing FRCA concrete) to improve the performance of FRCA concrete. However, these studies recommend the deployment of 30–50% FRCA as a substitute for natural fine aggregate. Additionally, the treatment methods are not cost-effective. To address these limitations and upscale the use of FRCA, this study introduces the particle packing method (PPM) for mix proportioning, a modified presoaking method for concrete mixing, and presents the effect of aggregate saturation level and paste content on the performance of concrete. Concrete mixes with 0–100% FRCA, 15% and 20% extra paste contents, and different aggregate saturation levels (50–100%) were prepared. The mechanical and durability properties of concrete, such as compressive strength, flexural strength, modulus of elasticity, abrasion resistance, sorptivity, water permeability, and chloride ingress, were analysed by replacing 0–100% crushed stone sand (CSS) with FRCA. The initial results showed a significant reduction in the mechanical and durability properties of fully saturated 100% FRCA concrete than the control mix. However, substantial improvement was seen by using partially saturated (50%) FRCA, and 20% paste content. The effect of decreasing FRCA saturation level was prominent. On using 50% saturated FRCA, the compressive strength, flexural strength, static and dynamic modulus of elasticity, and abrasion resistance, improved by 16%, 14%, 14%, 8%, 13%; and exhibited a lower sorptivity, water permeability, and chloride ingress of 56%, 14%, and 34%, respectively. The microstructural analysis showed that by reducing the saturation level and increasing the paste content a denser interfacial transition zone can be obtained. Furthermore, using PPM for mix proportioning is beneficial in minimizing the cement content for FRCA concrete mixes. The study demonstrates the synergistic effect of the PPM mix proportioning method, modified mixing method, 20% extra paste content, and partially (50%) saturated FRCA in improving the performance of untreated high-volume FRCA concrete, thereby supporting a sustainable approach.
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    Novel LCA-centric mix design approach for alkali-activated EAF slag with hybrid optimization techniques
    (Springer, 2024-12) Lahoti, Mukund; Pradhan, Subhasis
    This study presents an innovative life cycle assessment (LCA)-centric approach for optimizing the mix design of alkali-activated materials (AAMs) as sustainable alternatives to ordinary portland cement (OPC). The AAMs are developed using electric arc furnace slag (EAFS) and fly ash as precursors. The environmental performance is evaluated using the ReCiPe midpoint methodology, considering both mass and economic allocation methods. The results indicate that global warming potential and terrestrial ecotoxicity are the primary environmental impact categories across all mixes and allocation scenarios. A Taguchi-based hybrid optimization technique, integrating gray relational analysis (GRA) and analytical hierarchical process (AHP)-weighted GRA, is employed to determine the optimal mix design based on fresh properties, mechanical performance, durability, and sustainability indices. The AHP-GRA analysis reveals that mixes containing at least 50% EAFS perform better than OPC in terms of overall sustainability. A blend of 75% EAFS and 25% fly ash is recommended for achieving the best balance between performance and environmental impact, offering a promising alternative for sustainable construction practices.