Browsing by Author "Pradhan, Subhasis"

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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).
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.
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.
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.
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.
Impact of Particle Packing Method of Design Mix on Fracture Behavior of Concrete: Critical Analysis
(ASCE, 2020-04) Barai, Sudhir Kumar; Pradhan, Subhasis
This paper discusses the effect of the particle packing method (PPM) of mix design on the fracture behavior of concrete. A three-point bending (TPB) test was performed on single-edge notched beam for three different sizes. The fracture energy is estimated from theload (P)–crack mouth opening displacement (CMOD) relationship obtained from the TPB test. By truncating the end of the P–CMOD curveat different lengths, the sensitivity of fracture energy is analyzed, and eventually it is recommended to be at 2% of the depth of the beam.The fracture toughness parameters are calculated analytically using a double-Kfracture model. The size effect on the fracture energy andfracture toughness parameters is studied. The PPM mix design provides improved fracture energy and fracture toughness parameters ofconcrete with respect to the conventional mix design approach.
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.
Impact of service life and system boundaries on life cycle assessment of sustainable concrete mixes
(Elsevier, 2021-07) Pradhan, Subhasis
Partial substitution of cement/clinker in concrete mix helps reduce its environmental impact. The supplementary cementitious materials such as fly ash and ground granulated blast furnace slag (GGBS), and limestone calcined clay concrete (LC3) are thus been exploited without affecting the short-term performance of concrete. The long-term performance of concrete largely affects the service life of a structure and consequently the environmental impact during the service period. Hence, a comparative life cycle assessment study of four concrete mixes (controlled, fly ash blended (FA30), GGBS blended (GGBS50) and LC3) considering cradle-to-gate and cradle-to-grave system boundaries is conducted for the scenario in Singapore. The chloride resistance of these concrete mixtures is considered for service life estimation as it is the major cause for corrosion of the reinforcement. The uncertainty study reflects the dependence of service life on threshold chloride content. The service life is in the order of LC3 > FA30 > GGBS50 > controlled mix. LC3 and controlled concrete exhibit minimum and maximum environmental impact, respectively irrespective of system boundary. In cradle-to-gate system boundary, GGBS50 exhibits lesser environmental impact than FA30 excluding abiotic depletion, human toxicity, freshwater aquatic ecotoxicity and marine aquatic ecotoxicity impact categories owing to higher cement substitution level. However, the consideration of service life in cradle-to-grave system boundary resulted in lesser environmental impact for FA30 than GGBS50 in all impact categories (apart from acidification, GWP and terrestrial ecotoxicity), owing to the fewer repair cycles and subsequent utilization of concrete.
Influence of mechanical properties and CO2 emissions on the optimization of self-compacting based hybrid fiber reinforced concrete
(Elsiever, 2021-03-10) Barai, Sudhir Kumar; Pradhan, Subhasis
The paper deals with the development of high-performance self-compacting based concrete and optimization of the mix by accounting both mechanical and sustainability characteristics. Taguchi’s L16 orthogonal array is followed to consider 16 concrete mixes in combination of additives as four levels are considered for each additive/factor (class F type of fly ash, colloidal nano silica, crimped steel fiber, and polypropylene fibers). The global warming potential (GWP) is also estimated to account the sustainability parameter. To determine the optimized concrete mix satisfying both performance and sustainability characteristics the normalizing indices are used by accounting: (a) compressive strength and GWP, (b) split tensile strength and GWP, (c) flexural tensile strength and GWP, and (d) compressive strength, split tensile strength, flexural tensile strength and GWP. A detail comparison of normalizing indices is conducted, and the optimized concrete mix is determined based on the average rankings obtained from different normalizing index.
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.
Macro-level Performance Assessment of Concrete: Experimental Fracture Analysis
(Springer, 2024-02) Pradhan, Subhasis; Barai, Sudhir Kumar
Natural coarse aggregate (NCA) can potentially be replaced with recycled coarse aggregate (RCA), which is derived from the leftover concrete from construction and demolition (C &D) projects. However, RCA has drawbacks of its own, notably because of the porous mortar layer and micro-cracks. This motivates academics throughout the world to reduce the impact of the RCA’s inherent drawbacks in recycled aggregate concrete (RAC). Different mix design techniques, mixing procedures, the addition of fibres, and the addition of mineral admixtures are suggested in this context.
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.
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.
Partially hydrated recycled aggregate concrete: A systematic approach towards sustainable development
(Elsevier, 2018-10) Barai, Sudhir Kumar; Pradhan, Subhasis
The experimental investigation on the mechanical properties of partially hydrated recycled aggregate concrete (PHRAC) with the addition of polypropylene fiber (PP fiber) is carried out and compared with the conventional concrete. The 28 days compressive strength is observed to be higher for PHRAC, whereas the tensile strength is lower than natural aggregate concrete (NAC). Based on the mechanical properties, the optimal dosage of PP fiber for both NAC and PHRAC is obtained as 0.6% by weight of cement. The bond strength is also evaluated by conducting the pullout tests using rebar of 12 mm, 16 mm and 20 mm diameter. Higher bond strength is experienced for PHRAC with respect to NAC, whereas the PP fiber addition does not have a significant effect on the bond strength of concrete. Further, -test reveals that, barring flexural tensile strength other mechanical parameters are not influenced either by the type of aggregate or by the incorporation of PP fiber. The cost analysis shows that, the preparation of PHRAC is 4.5% cheaper than NAC.
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.
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.
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.
Performance Assessment of Concrete: Meso-, Micro-, Nano-level, and Physio-chemical Analysis
(Springer, 2024-02) Pradhan, Subhasis; Barai, Sudhir Kumar
The effect of microstructural characteristics on the macro-mechanical properties of concrete has been the subject of research over the last few decades. In chapters “Macro-level Performance Assessment of Concrete: Conventional Approach” and “Macro-level Performance Assessment of Concrete: Experimental Fracture Analysis”, it was examined how the type of aggregates, mix design techniques, and mixing methodologies affected macro-mechanical properties, which are thought to also affect meso-, micro-, and nano-level characteristics. Therefore, the current chapter focuses on how the aforementioned parameters affect the features and degree of hydration at the microstructure and mesostructure level. Additionally, both the ITZ and the entire specimen’s pore content and distribution are examined. The impact of each of these micro- and meso-level variables on the macro-mechanical properties is then examined at various curing times.
Performance of reinforced recycled aggregate concrete beams in flexure: experimental and critical comparative analysis
(RILEM, 2018) Barai, Sudhir Kumar; Pradhan, Subhasis
The necessity of sustainable approaches in the construction sector persuades the researchers to utilize the recycled coarse aggregate (RCA) extracted from waste concrete and study the performance of structural members by substituting natural coarse aggregate (NCA) with the RCA. In the present context, the flexural performance of RAC beam was examined on fourteen numbers of beams by completely replacing the NCA with RCA and using four different longitudinal reinforcement ratios (ρ) of 1.61, 1.31, 0.75 and 0.42%. In order to improve the quality of RAC, the particle packing method (PPM) of mix design approach was employed along with the two stage mixing approach (TSMA). The improved mechanical properties owing to the combined effect of PPM design mix and TSMA are also translated in the flexural performance of RAC beams even at 100% use of RCA. A maximum reduction of 35, 4 and 5% in cracking load, yield load and ultimate load, respectively, are observed in RAC beams as compared to the conventional concrete beams. However, the undesirable shear tension mode of failure was witnessed for RAC beams at ρ = 1.61%. A database is prepared by compiling the reported experimental results of RAC beams with shear reinforcement in the available literature. The suitability of the existing expressions to predict the ultimate load is verified for RAC beams and it is observed that, the number of unconservative predictions is significant. In this scenario, an equation is proposed to predict the ultimate load of transversely reinforced RAC beams by operating the flexure database, which shows good correlation with the available experimental results. Further, the increment in shear strength of RAC beams due to the inclusion of stirrups is estimated by using the derived expression.
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