Department of Civil Engineering

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Author: search.filters.author.Barai, Sudhir Kumar

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    Axial load prediction of circular hybrid double-skin tubular columns using interpretable gradient boosting machine learning models
    (Springer, 2026-01) Singh, Shamsher Bahadur; Barai, Sudhir Kumar
    This study assesses the predictive performance of three gradient-boosting Machine Learning (ML) models, Gradient Boosting Machine (GBM), eXtreme Gradient Boosting (XGBoost), and Light Gradient Boosting Machine (LightGBM), in axial load prediction of circular FRP-concrete-steel double-skin tubular columns (hybrid DSTCs). Data from 275 specimens were compiled from 22 publications in the literature to train and test ML models. Input variables consist of the height of column (), outer diameter of the FRP tube (), outer thickness of the FRP tube (), diameter of the inner steel tube (), thickness of the inner steel tube (), tensile strength of the outer FRP tube (), yield strength of the inner steel tube (), and compressive strength of concrete (), with the ultimate axial load () serving as the output variable. Performance of all three gradient ML models was evaluated using statistical measures including coefficient of determination (R2), root mean square error (RMSE), mean absolute percentage error (MAPE), and mean absolute error (MAE) for training and testing datasets. Results indicate that the XGBoost model performed better than the other two gradient Models (GBM and LightGBM) with R2 values of 0.97 on the training data and 0.95 on the testing data. Further analysis of the XGBoost model assessed the relative importance of input features on the output feature.
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    A simplified mix proportioning method for structural grade lightweight concrete using sintered flyash lightweight aggregate
    (Springer, 2026-01) Singh, Shamsher Bahadur; Barai, Sudhir Kumar
    Structural concrete of a designed strength can be produced for specific requirements by using the accepted methods of mix design but the present Indian standards on mix design does not takes into account the procedure for mix design of sintered flyash lightweight coarse aggregate based concrete. The sintered flyash lightweight aggregate mainly produced from ash generated from coal based thermal power plants has higher water absorption and lower specific gravity. The mix proportioning of sintered flyash lightweight coarse aggregate based concrete is reported to be cumbersome and less accurate than normal weight concrete as the water absorption characteristics of these aggregates is a main concern. The current study has been done to develop a simplified mix design procedure for production of structural grade lightweight concrete using commercially available sintered flyash lightweight aggregate. The study also highlights the procedure for corrections need to be done with respect to higher water absorption characteristics of sintered flyash lightweight aggregate taking into account effect of cement paste during concrete mix proportioning. Based on the developed mix design method, a trend of 28-day cube compressive strength versus w/c for sintered flyash lightweight aggregate based concrete has been plotted for wide range of w/c from 0.3 to 0.7 and compared with curve given in IS: 10262-2019 for normal weight concrete.
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    Green concrete : a sustainable construction material
    (Springer, 2025) Barai, Sudhir Kumar
    This book explores recycling and reusing construction wastes as alternative coarse aggregates and presents this as a possible solution for the major challenge of making sustainable concrete. It explores the reduction of cement use and the overcoming of some inferiorities in recycled coarse aggregate through the partial substitution of cement with supplementary cementitious materials (SCMs). The book evaluates the effect of low-volume SCMs (mainly fly ash) in 100% recycled coarse aggregate based concrete and comprehensively investigates this sustainable concrete for strength, safety, serviceability and sustainability. More specifically, this book discusses macro and microstructure properties, environmental impact assessment and performance of structural components. It explores the use of the particle packing mix design method (PPM) for concrete proportioning as it compensates lesser modulus of elasticity of RAC and is beneficial in lowering the environmental impact of concrete. Necessary modifications in mix design, mixing and design of concrete mixes are suggested to make this concrete safe for construction practice. It illustrates different mechanisms and results through figures, histograms, tables and experimental test pictures showing the failure pattern of structural elements and microstructure of concrete. Readers can get a clear understanding of the performance of this SCM incorporated RAC at various scales like micro, macro and structural components.
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    Empirical model for determining compressive strength using post-installed pull-out test for structural lightweight concrete made with sintered flyash lightweight aggregate
    (Wiley, 2025-06) Singh, Shamsher Bahadur; Barai, Sudhir Kumar
    In recent years, structural lightweight concrete has gained momentum in its use due to its superior properties in terms of dead load reduction, better thermal comfort, improved fire resistance, etc. The use of lightweight aggregates manufactured from industrial bi-products such as flyash presents an alternative to ever-depleting natural aggregates and has been the solution to environmental challenges and a circular economy. With the increase in the use of sintered flyash lightweight aggregate-based concrete (LC-SFA), there is a need to evaluate the applicability of existing empirical equations and models available to predict the on-site strength of concrete using the pull-out method. The pull-out technique for on-site strength estimation has been well researched for normal concrete (NC), but very limited studies have been reported for structural lightweight concrete. This study aimed to develop a model for the determination of on-site compressive strength from 20 to 50 MPa for lightweight concrete (LC) with sintered flyash lightweight aggregate with a high degree of predictability and accuracy using the non-destructive pull-out test, and compare the results with normal weight concrete. The pull-out method adopted in the study has demonstrated that the in-place compressive strength of concrete can be predicted with high accuracy and better repeatability of LC-SFA. The percentage variation in compressive strength predicted by different models varies from −2% to 80%. The proposed model for normal concrete and the model developed by Jensen and ACI for normal concrete gave values somewhat near to the experimental results of LC, however, the variation was more than 15% in the case of ACI, and in the case of Jensen, the values were on the lower side. The study revealed that existing empirical equations available for normal weight concrete to predict the compressive strength on the basis of pull-out force will not be applicable to lightweight concrete, and proposed a model based on a study conducted gives high accuracy and repeatability.
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    Empirical model for static and dynamic modulus of elasticity for sintered flyash lightweight aggregate based concrete
    (Springer, 2025-09) Singh, Shamsher Bahadur; Barai, Sudhir Kumar
    The present study developed a relationship between the (a) compressive strength and static Modulus of Elasticity (MOE), (b) compressive strength and dynamic MOE, and (c) the static MOE and dynamic MOE for sintered fly ash aggregates based concrete. This is the first detailed study to propose MOE models for concrete using sintered fly ash aggregates (SFA) validated across five mix designs and 120 specimens. The existing codes overestimate the MOE for SFA based lightweight concrete. To determine static MOE, the cylindrical specimens have been placed under uniaxial compression in strain-controlled mode, and a compressometer has been used to measure the MOE. The ultrasonic pulse velocity and dry density of concrete with different strength ranges were measured to evaluate the dynamic MOE of concrete produced using SFA. The MOE of concrete produced using SFA as coarse aggregate is around 30–35% lower than that of normal-weight concrete. The static modulus of elasticity of lightweight concrete with SFA ranged between 16 GPa and 27 GPa, whereas the dynamic modulus of elasticity of lightweight concrete with SFA ranged between 19 GPa and 28 GPa for a compressive strength range of 20–55 MPa. Based on the experimental results, an empirical equation has been developed for estimating static MOE and dynamic MOE, and the relationship between static and dynamic MOE. The developed equations have been compared with those in the codes and literature. The developed models enhance accuracy in structural analysis and design through reliable estimation of MOE, and propose an alternative, quick, and easy method to estimate dynamic MOE for SFA-based lightweight concrete using the ultrasonic pulse velocity method.
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    Probabilistic life cycle assessment of ash-based sintered lightweight aggregates manufactured with producer gas and coal-operated thermal power
    (Springer, 2025-09) Singh, Shamsher Bahadur; Barai, Sudhir Kumar
    The infrastructure growth in the world is expected to result in huge requirement of 12.5 billion tonnes of coarse aggregates in 2050. The utilization of artificial aggregates can pave a feasible pathway for tackling the issue of scarcity of natural aggregates. Life cycle assessment (LCA) is an environment management tool, which has been used for the large-scale acceptability of sintered flyash lightweight aggregates (SFLA) in the construction fraternity. The low quality of data inputs for LCA study induces bias and increase in uncertainty of evaluated impacts. In the current study, a probabilistic LCA framework has been developed for assessing the environmental impacts from the manufacturing of SFLA. The uncertainty distribution range in each of the input variables was identified and introduced in the model with the help of random numbers. In this study, uncertainty analysis is also carried out using Monte Carlo Simulation for the comparative analysis of baseline scheme with three alternative schemes of SFLA manufacturing process. Finally, the sensitivity analysis (SA) was also undertaken for studying the robustness of LCA model outputs. The global warming potential (GWP) for the baseline scenario is 198.6 kg CO2 eq. per t of SFLA. Three alternative schemes were proposed for which comparative impact assessment is carried out, which highlighted the GWP impacts reduces to 166.7 kg CO2 eq. per t of SFLA (16% lower), 142.6 kg CO2 eq. per t of SFLA (28% lower) and 123.4 kg CO2 eq. per t of SFLA (38% lower) for first, second and third alternative schemes respectively as compared to the baseline scheme. Sintering process is contributing highest to impact mainly due to emissions from combustion of coal present in raw mix, CO2 emissions from electricity consumed during the process and CO2 generated from producer gas production which is used for thermal energy in sintering process. The results of probabilistic LCA study show that there are significant variations in the coefficient of variation across the various unit processes and across the four impact categories.
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    Production and characterization of materials
    (Springer, 2025-10) Barai, Sudhir Kumar
    In the previous chapter, we have discussed the pressing need for a durable and green concrete. Use of recycled concrete aggregates as coarse aggregate replacement and other SCMs as partial cement substitute can become potential alternative constituents in concrete. Aggregates constitute 75–80% of the volume of concrete. In this chapter, we will mainly discuss the production of coarse recycled concrete aggregates which are obtained by recycling, sorting, and processing of the construction demolition wastes at the end-of-life of a concrete structure. Thus, waste collection, segregation, and processing methods to prepare them for use as coarse aggregates in concrete are discussed. While aggregates are mostly inert materials which do not participate actively in chemical reactions, their qualities can still impact the fresh and hardened properties of concrete. Thus, it is crucial to understand the properties of recycled aggregates in contrast to natural aggregates. When we fully substitute recycled coarse aggregates for natural coarse aggregates, it is interesting to see how the characteristics of the coarse aggregates impact the performance of concrete at macro-level. This chapter also discusses the properties of commonly available SCMs, like fly ash, slag, and silica fume, which can be utilized to positively modify the performance of RAC.
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    Microstructure properties
    (Springer, 2025-10) Barai, Sudhir Kumar
    Concrete comprises of three different phases such as (1) aggregate, (2) hardened cement matrix and (3) interfacial transition zone (ITZ) between the aggregate and matrix. Heterogeneity in concrete at the microstructural level is caused mainly due to the non-uniform distribution of water in the zone near an aggregate edge and that farther from the aggregate that is in the matrix region. Phenomena which occur closer to an aggregate surface in concrete are: (1) availability of more water which facilitates formation of larger size capillary voids after hydration (2) growth of preferentially oriented layer of crystalline hydrated products (mainly calcium hydroxide) and (3) development of microcracks even prior to loading. Moreover, the microstructure rather than being fundamentally constant, varies with curing ages. Presence of aggregates in general (due to wall effect) and types of aggregate such as recycled coarse aggregate in particular result in a complicated and inhomogeneous microstructure than the plain cement paste. The layer of adhered mortar on the surface of recycled coarse aggregate makes the interface more complex. In this chapter, we will try to find out answer to the following questions: How does incorporation of supplementary cementitious materials alter the aggregate-matrix interface in recycled aggregate concrete? How do the microstructural properties affect the macro behaviour of concrete?
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    Environmental impact of concrete
    (Springer, 2025-10) Barai, Sudhir Kumar
    Sustainable 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.
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    Behaviour of reinforced concrete slabs under punching shear
    (Springer, 2025-10) Barai, Sudhir Kumar
    Flat slab supported by an interior column is a complicated problem due to the most likely phenomenon of punching shear failure. This chapter discusses the punching shear behaviour of recycled aggregate concrete with coarse RCA. In the context of using SCMs in concrete, we address the following question: How does low-volume fly ash as a cement substitute alter the punching shear of RAC flat slabs? Another aspect while using any recycled material is maintaining the level of structural safety as that of the already existing material. The punching shear resistance design equation, available for the standard reinforced concrete slabs, may not yield a safe design for RAC slabs due to greater uncertainties. The reliability of standard punching shear models is assessed and modified to ensure equivalent safety for RAC and NAC flat slabs. It is crucial to conduct this reliability analysis in order to confidently establish fly ash and 100% coarse RCA as alternative concrete constituents in practice.