BITS Faculty Publications

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Author: search.filters.author.Pradhan, SubhasisSubject: search.filters.subject.Recycled aggregate concrete

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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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    Construction and Building Materials Shear performance of recycled aggregate concrete beams: An insight for design aspects
    (Elsevier, 2018-07) Barai, Sudhir Kumar; Pradhan, Subhasis
    The shear failure of reinforced concrete beam is a brittle type of failure and can be dangerous if it is not properly designed. The inherent inferior quality of recycled coarse aggregate (RCA) makes the recycled aggregate concrete (RAC) beams even more vulnerable in shear resistance. This persuades the structural designers to account each of the contributing components in the shear resistance mechanisms seriously, especially that of concrete. In this regard, an experimental investigation was carried out on fourteen beams to examine the shear performance of RAC beams in the absence and presence of transverse reinforcement. Six numbers of beams without transverse reinforcement were tested to examine the contribution of RAC in shear resistance mechanisms and eight beams with shear reinforcement were tested to verify the applicability of the prevailing shear design provisions for RAC beams. The inferior mechanical properties of the RAC are improved satisfactorily by implementing the Particle Packing Method of mix design approach along with the established Two Stage Mixing Approach. However, even with the improved mechanical properties of RAC, the poor performance of RAC beams in shear could not be avoided and a drop of 14% was recorded in the ultimate shear strength of RAC beams without stirrups. A database is prepared by compiling the reported test results of RAC beams with and without transverse reinforcement. An alternative equation is proposed to predict the diagonal tension cracking strength of RAC beams, by using the database of RAC beams without transverse reinforcement and it exhibits a better correlation with the experimental results. Further, in the shear resistance mechanisms of RAC beams the effectiveness of stirrups is studied using the database of RAC beams without and with transverse reinforcement.
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    Impact of particle packing mix design method on fracture properties of natural and recycled aggregate concrete
    (Wiley, 2018-11) Barai, Sudhir Kumar; Pradhan, Subhasis
    The fracture properties of four types of concrete prepared using natural coarse aggregate and recycled coarse aggregate and conventional and particle packing method (PPM) of mix design approaches are studied. The three-point bending (TPB) test is performed using three different sizes of single edge notched beam. The fracture energy is calculated from the load-CMOD curve obtained in the TPB test, and in this process the load-CMOD curve is curtailed at 2% of the depth of the beam. Based on CTODc and w1 relationship, appropriate softening function is used to estimate the double-K fracture parameters. The fracture energy and fracture toughness parameters of recycled aggregate concrete (RAC) is inferior to the natural aggregate concrete (NAC). The PPM mix design improves the fracture properties of concrete in comparison to the conventional mix design approach. The fracture properties of PPM mix designed RAC are comparable to that of NAC prepared using conventional method.
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    Comparative LCA of recycled and natural aggregate concrete using Particle Packing Method and conventional method of design mix
    (Elsevier, 2019) Barai, Sudhir Kumar; Pradhan, Subhasis
    In construction industry, apart from cement, the aggregate type, mix design method and transport distance of raw materials also contribute significantly to the environment related issues. This paper compares environment impacts of recycled coarse aggregate (RCA) and Particle Packing Method (PPM) of mix design approach with the concrete proportioned using natural coarse aggregate (NCA) and IS code method. The system boundary is determined based on cradle-to-gate theory. The primary data regarding the preparation of NCA and RCA are collected from the respective production facilities and Ecoinvent 3.01 is used as background database. Abiotic depletion, abiotic depletion due to fossil fuels, global warming potential, depletion of ozone layer, formation of tropospheric ozone photochemical oxidants, acidification potential, and eutrophication potential are measured using CML baseline method with the help of SimaPro software. Lower environmental impacts are observed for PPM mix designed concrete owing to the requirement of lesser cement quantity. The combination of RCA and PPM mix design approach exhibits minimum environmental impacts. Transport activities are the second largest contributor after cement and hence, sensitivity analysis is carried out to evaluate the influence of different transport scenarios and distances in Indian context. For comparable environmental impact with natural aggregate concrete proportioned using IS code method, the maximum possible supply distance of RCA is determined for different collection distance of C&D waste. The collection distance of C&D waste can be incremented by 9–12 km for each 50 km increment in the supply distance of processed RCA to prepare recycled aggregate concrete.
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    Multi-scale characterisation of recycled aggregate concrete and prediction of its performance
    (Elsevier, 2020-02) Barai, Sudhir Kumar; Pradhan, Subhasis
    The inherent inferior quality of recycled coarse aggregate (RCA) influences the microstructural characteristics and consequently, the macro-mechanical properties of recycled aggregate concrete (RAC). The present paper investigates the influence of aggregate properties, degree of hydration (), and micro and meso level characteristics of concrete on its compressive strength. Moreover, the influence of different mix design methods (conventional and Particle Packing Method) and mixing approaches (normal mixing approach and two stage mixing approach) on , and micro and meso level properties of concrete are analysed. In addition to the crushing value and water absorption of coarse aggregate, thermogravimetric analysis, nanoindentation and image analysis of back-scattered electrons images and X-ray microtomography images are performed to measure , interfacial transition zone (ITZ) thickness, voids content in the ITZ and interface of concrete, respectively. However, none of these parameters can be singled out to demonstrate its major or significant contribution to the compressive strength of concrete. Hence, the influence of each parameter must be appreciated. An expression is proposed by accounting each of these parameters and also the cement content and coarse aggregate fraction to predict the compressive strength of concrete, which exhibits good correlation with the experimental results.