BITS Faculty Publications
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Item Simulation of Cyclic Mean Stress Relaxation and Ratcheting for Aluminium 7050 Alloy(Springer, 2022-02) Barai, Sudhir KumarThe study attempts to simulate the cyclic-plastic behaviour of aluminium 7050 alloy under uniaxial asymmetrical strain- and stress-controlled fatigue loading which is primarily characterized by the two phenomena: (a) cyclic mean stress relaxation and (b) ratcheting. The suggested approach considers the Chaboche combined hardening model; the parameters of the Chaboche model are estimated using genetic algorithm optimization technique. The proposed methodology provides a single set of hardening parameters, which are used to simulate the cyclic-plastic response under both strain- and stress-controlled cyclic loading. Reported experimental results on aluminium 7050 alloy are used to demonstrate the potential of the proposed methodology; the accuracy of the suggested methodology is compared with some reported simulations for the material in the existing literature.Item Temperature, porosity and strength relationship for fire affected concrete(Springer, 2022-02) Barai, Sudhir KumarIn a fire incident, structural members are mostly unevenly exposed to temperatures and consequently suffer uneven damage. To rehabilitate and restore these for future usage, it is essential to correctly map the temperature field that the structural elements were subjected to during fire events. The majority of the existing relationships for temperature prediction apply to reinforced concrete beams only. In the present study, a material-porosity-based approach is proposed. Normal and high strength concrete structural elements were exposed to a range of elevated temperatures, and reserved compressive strength was evaluated. Another set of the same specimens were used to determine porosity using four techniques. Based on the observations, correlations among temperature, strength, and porosity for normal and high strength concrete are proposed. The suggested methodology and expressions may be used to predict the reserved strength and temperature field that the structural elements may have been exposed to, based on the evaluated porosity of concrete. Back-scattered electron Imaging was found to be the most fitting method for porosity evaluation.Item Biocement treatment for upcycling construction and demolition wastes as concrete aggregates(Springer, 2022-06) Barai, Sudhir KumarReutilisation of the construction and demolition (C&D) wastes as aggregate in concrete is a vital step towards sustainability as it prevents depletion of natural resources as well as alleviates wastes. However, the attached mortar on the aggregate surface renders certain shortcomings like excessive water absorption, high porosity, and weak interfaces. Recycled aggregates can be treated to improve these shortcomings. However, the minimisation of the drawbacks involves huge energy, materials, and cost. Moreover, the efficacy of such adopted method is sometime questionable, and which needs further research. This study demonstrates bio-treatment of recycled coarse aggregate (RCA) as a means of upcycling and compares it with conventional cement slurry treatment. A novel spraying technique has been applied that significantly economises biocement treatment. The experimental results show that biocement treatment reduced the water absorption by 70%. The treatment has filled the pores of RCA and has prevented water absorption. In contrast, cement slurry coating treatment shows increase in water absorption of RCA by 19%. The compressive strength of concrete with 100% biocement treated RCA surpasses that of concrete with natural coarse aggregates. The genesis of this dramatic improvement in case of biocement has been established through micro-scale studies including scanning electron microscopy and energy-dispersive X-ray spectroscopy. The cost analysis demonstrates that RCA upcycled with biocement treatment is more economical than natural aggregates or cement treated ones. Findings of the present study led to the conclusion that 100% replacement of natural coarse aggregates can be achieved by upcycling C&D wastes as coarse aggregate through bio-treatment.Item Performance assessment and life cycle analysis of concrete containing ferrochrome slag and fly ash as replacement materials – A circular approach(Elsevier, 2022-09) Barai, Sudhir KumarClimate change mitigation and resource efficiency have emerged as crucial challenges for long-term sustainability of concrete. Implementing circular approach through waste valorisation in concrete production with eco-efficient mix design is an efficient mitigation pathway to combat natural resources depletion and environmental issues. This paper investigates techno-environmental sustainability of concrete utilizing 100% ferrochrome slag as alternate coarse aggregate and fly ash as partial cement substitute (0–40%) adopting particle packing optimization technique (PPOT) as a sustainable mix design method. Total of ten types of concrete mixtures were prepared using the alternate materials and mix design methods (PPOT and IS:10262(2009)). Natural aggregate concrete prepared by IS:10262(2009) mix design was considered as the reference mixture. Technical assessment of concrete was performed experimentally in terms of compressive strength and tensile strength. Environmental performance was investigated through life cycle assessment (LCA) as per ISO 14040-44 guidelines using cradle-to-gate system boundary and two functional units: 1 m3 concrete and 1 MPa compressive strength. Results revealed that ferrochrome slag aggregate concrete (FCSAC) containing fly ash up to 30% prepared by PPOT has enhanced strength than reference concrete. Regardless of the functional units used, FCSAC with 30% fly ash designed by PPOT was ranked as the most sustainable mix with significant environmental savings (around 50–70%) without compromising desired requirements. Sensitivity analysis was performed by varying transportation distance, mode of transport and energy mix. Results showed that FCSAC with 30% fly ash is not sensitive to the scenarios investigated. The outcomes will be helpful for decision-makers to develop policy directives and frameworks on synergistic use of ferrochrome slag and fly ash towards concrete sustainability.Item Performance of concrete made using sintered fly ash lightweight aggregate-a review(India Concrete Journal, 2023) Singh, Shamsher Bahadur; Barai, Sudhir KumarCurrent work summarizes research done on potential of sintered fly ash lightweight aggregate based concrete and its suitability as an aggregate. The manuscript presents physical and chemical parameters of ingredients such as fly ash as well as binders adopted in manufacturing process covering effect of these materials on parameters related to pelletization like duration, angle of inclination and rotation speed and its subsequent effect of aggregate characteristics. The impact of sintering temperature and its duration on aggregate characteristics is also discussed. The physio-chemical and mechanical characteristics of sintered fly ash aggregate is briefly presented. The review of literature suggests that specific gravity and water absorption of sintered fly ash lightweight aggregate is low and high respectively as compared to conventional aggregate. The use of additives such as alkaline activators, styrene-butadiene rubber, quick lime etc. and additional treatments such as coating or vacuum impregnation has shown potential for reducing water absorption. The mechanical performance of sintered fly ash lightweight aggregate in concrete is different from normal concrete. Factors affecting compressive strength, flexural strength and modulus of elasticity apart from the characteristics of manufactured sintered fly ash lightweight aggregate are cement content, supplementary cementitious materials, additives used, treatment done to aggregate, aggregate content, shape index of aggregate etc. Studies have indicated no direct relationship between factors affecting concrete durability such as water absorption, mechanical perfromance, cement content, water penetrability and freeze-thaw resistance of sintered fly ash lightweight concrete.Item A New Technology for Full Replacement of Natural Aggregates with Bioremediated Recycled Aggregates and Its Lifecycle Assessment(Springer, 2024-02) Barai, Sudhir KumarThe problem of construction and demolition wastes can be mitigated by recycling them as aggregates in concrete. However, high absorption and poor interfacial properties due to the attached mortar from old concrete use a major weakness resulting in only a partial replacement of natural aggregates with the recycled ones. This paper discusses a technique, bioremediated recycled aggregates (BRA), to bring their performance at par with the natural aggregates (NA). A biocement treatment has been applied to strengthen the attached mortar. The performance concrete with NA and 100% BRA is assessed for strength, water absorption, microstructure (using SEM with EDS) and micromechanical properties (using nanoindentation). It is observed that bio treatment recovers the performance of recycled aggregates at par with that of NA. The lifecycle analysis has demonstrated that BRA is clearly more sustainable than NA.Item Flexural behaviour of fly ash incorporated ferrochrome slag aggregate reinforced concrete beam(Elsevier, 2023-10) Barai, Sudhir KumarThe structural behaviour of fly ash integrated ferrochrome slag aggregate concrete (FCSAC) is not widely understood owing to lack of research, although some studies have focused on its mechanical and environmental performance. The real-world use of FCSAC relies on its large-scale structural tests. This research investigates the flexural response of reinforced concrete beams fabricated with fly ash and ferrochrome slag (FCS) aggregate. A total of sixteen full-scale beams were built and tested. The beams were cast using four different concrete compositions: natural aggregate concrete (NAC) without any fly ash and FCS as the reference; FCSAC comprising 100% FCS as coarse aggregate and fly ash as partial substitution of cement at different percentages: 0%, 20% and 30%. The beams were fabricated with two different longitudinal reinforcement ratios of 0.69% and 1.86%. An eco-efficient mix proportioning method based on Particle packing optimization technique (PPOT) was adopted aiming to develop sustainable concrete. The effect of alternate resources (FCS and fly ash) and reinforcement ratios on the flexural response, cracking, ultimate load, failure pattern, ductility and toughness were examined. The experimental outcomes were compared to the predictions derived from the existing code provisions. Results revealed that the flexural performance of the FCSAC with fly ash beams was superior to that of NAC beam, despite having a lower flexural capacity than the FCSAC without fly ash beams. Moreover, the comparative study demonstrated that the fly ash-based FCSAC beams may be designed in accordance with the same guidelines as conventional concrete.Item Effective method for upcycling construction and demolition waste into concrete: A life cycle approach(Sage, 2023-06) Barai, Sudhir KumarDifferent property enhancement techniques have already been established to support upcycling of construction and demolition waste as aggregate in concrete. However, the most suitable and sustainable method is still unknown. Quality improvement of recycled coarse aggregate (RCA) after any treatment method and its environmental impact is estimated using life cycle analysis (LCA). This article compares the environmental impacts of such treatment methods on RCA and aims to find out the most suitable method with minimum impacts. The functional unit of this study is considered the preparation of 1 tonne of treated aggregate (recycled), considering reduction in water absorption after the treatment. An LCA is carried out using the SimaPro software (https://simapro.com/) followed by ISO 14040/44 guidelines. Based on the LCA environmental profiles, thermal treatment is the highest emission contributing removal method followed by mechanical grinding. In strengthening of attached mortar methods, accelerated carbonation process is the major emission contributing method followed by a specific microbial treatment. Moreover, a sensitivity analysis was performed by varying the energy mix with a focus on renewable-based energy mix. The sensitivity analysis shows a shift on selection for the suitable treatment method and other possibilities considering renewable-based energy mix. A preliminary assessment and probable impact prediction could be conceptualized before the adoption of any treatment method on RCA for a particular location.Item Experimental and Nonlinear Finite Element Simulation of Compressive Behavior in Natural FRP-Concrete-Steel Double-Skin Rectangular Tubular Columns(Springer, 2024-06) Singh, Shamsher Bahadur; Barai, Sudhir KumarThis study addresses the research gap regarding using natural fibre-reinforced polymers (FRPs) to construct hybrid Double-Skin Tubular Columns (DSTCs). Experimental testing on twelve rectangular specimens revealed critical failure mechanisms primarily due to the rupture of FRP tubes under excessive stress. This rupture led to the loss of lateral support for the concrete, resulting in severe crushing and localized buckling of the inner steel tube. The experimental results also showed an 18% increase in axial stress and 18 times enhancement in axial strain within confined concrete specimens compared to unconfined concrete specimens because of the effective confinement provided by the outer natural FRP tube (hemp fibre). By integrating experimental and nonlinear finite element simulations, this study highlights the structural performance of these hybrid DSTCs under axial compression, with an average deviation of 1% at the peak axial load, demonstrating the effectiveness of the numerical simulation model. Additionally, a parametric study using validated nonlinear finite element analysis (NLFEA) models to investigate the influence of outer tube cross-sectional aspect ratio, inner steel tube shape, and outer FRP tube thickness on the confined concrete in rectangular DSTCs has been carried out. The finding highlighted that rectangular DSTCs with thicker FRP tubes exhibit higher ultimate axial stress and strain in the confined concrete. Moreover, rectangular DSTCs with square inner steel tubes showed notably lower ultimate axial stress and strain in the confined concrete than rectangular DSTCs with circular inner steel tubes. This comprehensive study emphasizes the importance of stress–strain models, offering valuable insights for the design and construction of hybrid rectangular DSTCs.Item Shear behavior of reinforced concrete beams incorporating ferrochrome slag aggregate and fly ash(Springer, 2024-07) Barai, Sudhir KumarFerrochrome slag aggregate concrete (FCSAC) incorporated with fly ash offers multiple benefits over FCSAC alone and natural aggregate concrete (NAC) in terms of durability and environmental impacts, without sacrificing essential strength. However, structural behavior of fly ash-based FCSAC is poorly understood due to lack of investigations. This study examined shear performance of 16 full-scale reinforced concrete beams. FCSAC was prepared using 100% FCS coarse aggregate and fly ash as fractional cement replacement (0%, 20% and 30%). To completely comprehend the shear resistance mechanism of FCSAC, eight beams were built without shear reinforcement and eight with it. NAC and FCSAC (without fly ash) were considered as the reference beams. Existing design guidelines and fracture mechanics approaches were verified to predict shear capacity of FCSAC beams. The findings of the study revealed that fly ash incorporated FCSAC beam exhibited fewer cracks and higher shear capacity (about 7%) than NAC beam, but lower strength (about 8%) than FCSAC without fly ash beam. Shear provisions outlined in CSA provisions and fracture model by Gastebled and May could be adopted for FCSAC (with or without fly ash) beams without risk. This research demonstrates that fly ash-based FCSAC can be utilized safely for structural purposes.