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Item Environmental impact of concrete(Springer, 2025-10) Barai, Sudhir KumarSustainable concrete production demands satisfaction of the two most important criteria such as optimization of resources and minimization of end-of-life wastes. As discussed in the previous chapters, one of the important ways in which this can be achieved is by using coarse recycled concrete aggregates (RCAs) as an alternative to natural coarse aggregates and other industrial wastes as supplementary cementitious materials (SCMs). In this regard, the role of a suitable mix design method for obtaining an optimum combination of concrete constituents is also significant. In this chapter, sustainability of 100% recycled coarse aggregate concrete (RAC) along with SCMs in concrete is explored through performing life-cycle assessment, especially focusing on concrete with coarse RCA and low-volume fly ash as cement substitute (denoted as FARAC) in concrete. The effect of particle packing method (PPM) of mix proportioning on the environmental impact of FARAC is assessed for a case study of India.Item Mixing and mix proportioning methods(Springer, 2025-10) Barai, Sudhir KumarConcrete performance depends not only on the constituent materials but also on the proportions in which the materials are mixed and the order of mixing during casting. So, the constituents of known qualities need to be proportioned accordingly to achieve concrete of desired performance. This chapter explores the utilization of the particle packing method for mix design, specifically for determining the appropriate proportions of fly ash and coarse recycled concrete aggregate (RCA) in concrete. The effects of mixing methods such as two-stage and triple mixing are also discussed in this context.Item Particle packing method for recycled aggregate concrete(Springer, 2024) Pradhan, Subhasis; Barai, Sudhir KumarThis 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.Item Aggregate presaturation and concrete mixing technique for upscaling the use of fine recycled concrete aggregate(Elsevier, 2025-06)The porous structure of fine recycled concrete aggregate (FRCA) affects the properties of concrete and limits its use beyond 30 %. This study aims to improve the quality of concrete prepared with 100 % FRCA. Past work confirmed that the aggregate saturation level and concrete mixing methods influence the performance of FRCA concrete. To upscale the use of FRCA, a new modified presoaking method for mixing FRCA concrete is proposed, along with assessing the effect of three saturation levels (50 %, 75 %, and 100 %) and four mixing methods: conventional, presoaking, two-third presoaking, and modified presoaking. The compressive strength, flexural strength, static and dynamic modulus of elasticity, and the density of the interfacial transition zone (ITZ) were examined. Results showed that concrete with partially saturated FRCA exhibited better mechanical properties. The modified mixing method provided consistent results and an ITZ with lesser void content, indicating higher reliability than the conventional, presoaking, and two-third presoaking methods. At a 50 % saturation level of FRCA, the results for the modified presoaking method showed higher compressive strength, flexural strength, static, and dynamic modulus by 10 %, 9 %, 12 %, and 20 %, respectively, in comparison to concrete mixed by a conventional method consisting of 100 % saturated FRCA. This work provides clarity on appropriate processes and practices for the utilization of FRCA in concrete and facilitates a circular economy in the construction industry.Item Construction and Building Materials Shear performance of recycled aggregate concrete beams: An insight for design aspects(Elsevier, 2018-07) Barai, Sudhir Kumar; Pradhan, SubhasisThe 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.Item Comparative LCA of recycled and natural aggregate concrete using Particle Packing Method and conventional method of design mix(Elsevier, 2019) Barai, Sudhir Kumar; Pradhan, SubhasisIn 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.Item Multi-scale characterisation of recycled aggregate concrete and prediction of its performance(Elsevier, 2020-02) Barai, Sudhir Kumar; Pradhan, SubhasisThe 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.Item Shear performance of recycled aggregate concrete beams: An insight for design aspects(Elsiever, 2018-07-30) Barai, Sudhir KumarThe 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.Item Multi-scale characterisation of recycled aggregate concrete and prediction of its performance(Elsiever, 2020-02) Barai, Sudhir KumarThe 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.Item Recycled aggregate concrete incorporating fly ash: Comparative study on particle packing and conventional method(Elsiever, 2017-12-15) Barai, Sudhir KumarIn the present study, particle packing method (PPM) of mix proportioning is applied in a novel way for recycled aggregate concrete (RAC) incorporating fly ash as a partial replacement of cement. Lesser fresh mortar content was achieved by PPM which resolves the major concern of excess adhered mortar in RAC. Theoretical packing density (PD) obtained using compaction-interaction packing model was compared with experimental PD. 18% and 28% reduction in cement content was observed for RAC with 20% and 30% fly ash replacement respectively due to PPM mix proportions as compared to conventional method at water-binder ratio of 0.45. Compressive strength, flexural strength and modulus of elasticity of RAC with fly ash showed comparable results with natural aggregate concrete in PPM. The rate of long term compressive strength gain was about 11%–20% and 30% in RAC and natural aggregate concrete (NAC) respectively. Split tensile strength and modulus of elasticity in RAC was comparable in both the conventional as well as PPM methods. Flexural strength was improved in RAC incorporating fly ash mix due to PPM. Statistical analysis showed better tensile strength for RAC as compared to NAC up to the characteristic compressive strength of 25 MPa. Poor tensile behaviour was reported for high strength recycled aggregate concrete. The results suggest that, the particle packing method can be used in RAC with fully replaced recycled aggregates incorporating fly ash (up to 30% replacement) for sustainable construction practices.