BITS Faculty Publications

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

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    Experimental and numerical study of recycled aggregate concrete column
    (Wiley, 2023-02) Pradhan, Subhasis; Barai, Sudhir Kumar
    The improved mechanical properties of recycled aggregate concrete (RAC) by employing the particle packing method (PPM) of the mix design approach encourages its application to study the performance of structural members. The experimental investigation is conducted on the axial compressive behavior of reinforced natural aggregate concrete (NAC) and RAC columns using two different tie spacing conditions. A reduction of 18% in the axial load of RAC columns is observed with respect to the NAC columns and only 2.7% improvement in axial load is recorded as the tie spacing reduces by 22.5%. Subsequently, the finite element (FE) analysis is conducted to investigate the axial compressive strength of both NAC and RAC columns using different tie spacing conditions. The FE analyses of RAC columns with different tie spacing support to modify the spacing of transverse reinforcement as half as that of the spacing specified in the prevailing design for NAC columns.
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    A thermo-mechano-chemical activation technique to use quartz rich marine clay for one-part geopolymer preparation
    (Elsevier, 2023-07) Pradhan, Subhasis
    This research aims to prepare one-part geopolymer by using the quartz rich marine clay available in Singapore. The higher quartz and lower kaolinite mineral (∼29%) in marine clay is not ideal for a precursor material in geopolymerization. Hence, a novel thermo-mechano-chemical activation process is employed. The process of thermal activation (calcination at 850 C) transforms kaolinite into reactive metakaolin form. The mechanical activation by ball milling alters the surface group of quartz by forming non-bridging oxygen. The chemical activation process is promoted by adding alkali materials, such as NaOH, Na2CO3, and Ca(OH)2. XPS results inform the presence of higher non-bridging oxygen content in Na2CO3 and NaOH based mixtures than Ca(OH)2 based mixture. However, more reactive Q0(0Al) and Q1(1Al) states of 29Si are observed in Ca(OH)2 based mixture from NMR spectra. This resulted in higher compressive strength of Ca(OH)2 based one-part mixture. A temperature curing (at 80 C) is required to facilitate the geopolymerization process.
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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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    Characterization of Materials
    (Springer, 2024-02) Pradhan, Subhasis; Barai, Sudhir Kumar
    Concrete is a composite material and a heterogeneous mixture of cement, coarse aggregate, fine aggregate, water, and chemical admixture. The behaviour and performance of concrete in the fresh as well as hardened stages largely depend on the physical, mechanical, and chemical properties of its constituents. Hence, it is important to determine the characteristics of the raw materials prior to the designing of concrete mix for their intended application. This book aims to compare the performance of concrete, prepared using two different types of coarse aggregates (natural coarse aggregate (NCA) and recycled coarse aggregate (RCA)). The subsequent sections exclusively discuss the differences in physical and mechanical properties between NCA and RCA.
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    Structural Applications: Beam
    (Springer, 2024-02) Pradhan, Subhasis; Barai, Sudhir Kumar
    The fundamental characteristics of RCA and how it is used to create RAC were covered in prior chapters. In this context, the influence of the PPM mix design technique was explored.
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    Life Cycle Assessment and Cost Analysis
    (Springer, 2024-02) Pradhan, Subhasis; Barai, Sudhir Kumar
    The researchers suggested various mix design techniques and mixing strategies to prepare RAC with acceptable mechanical characteristics.
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    Background on Techniques for Sustainable Use of Recycled Aggregate and Application of Particle Packing Method
    (Springer, 2024-02) Pradhan, Subhasis; Barai, Sudhir Kumar
    Concrete is an attested building material because of its versatility and cost-effectiveness. Thus, it is the second most consumed material in the world after water (ISO/TC 71, 2005; Weil et al., 2006; Knoeri et al., 2013). Its production and use is escalated by about 12 times since the Second World War and in present scenario the yearly per capita concrete production is about 4.8 tonnes (Monkman and MacDonald, 2017).
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    Production and Processing of Aggregates
    (Springer, 2024-02) Pradhan, Subhasis; Barai, Sudhir Kumar
    In India, the extensive use of reinforced concrete and prestressed concrete structures happened in the second half of the nineteenth century. At the time of construction, the reuse of building waste after their service life was not thought about. The destruction of structures due to natural disasters is inevitable. Moreover, replacement of old structures with new and higher capacity structures is essential in order to satisfy the need of the growing population and traffic. Uncontrolled demolition of old structures is a problem owing to the improper waste management. At the same time, the waste concrete from ready-mix plant, laboratory-tested specimens, and rejected precast concrete members aggravate this issue
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    Particle Packing Method of Mix Proportioning and Modified Mixing Approach
    (Springer, 2024-02) Pradhan, Subhasis; Barai, Sudhir Kumar
    One of the main industries responsible for the rapid depletion of natural resources and the production of greenhouse gases in order to obtain the essential raw materials is the construction industry. To ease the strain on natural aggregate mining, aggregates, which make up around 70—80% of the volume of concrete, must be replaced with a sustainable alternative. Additionally, the construction industry and the generation of C &D trash go hand in hand. Natural aggregate can potentially be replaced with recycled aggregate (RA), which is produced from leftover concrete from the C &D waste. RA can be divided into RCA and RFA categories according to size. The use of RCA alone for structural concrete preparation is the exclusive focus of this work.
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    Structural Applications: Slab
    (Springer, 2024-02) Pradhan, Subhasis; Barai, Sudhir Kumar
    The performance of RAC in both the fresh and hardened stages is adversely affected by the inherent inferior material qualities of RCA caused by the existence of micro-cracks and attached mortar layer. PPM mix design approach is used in conjunction with the TSMA to reduce the impact of RCA and enhance the quality of RAC, as detailed in Chapters 4 and 5. Results from the experimental research on the punching shear performance of RAC slabs with 100% RCA use were inconsistent.