Faculty Publications
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Item Mineralogical study of concretes prepared using carbonated flyash as part replacement of cement(Springer, 2019) Sahoo, S.; Das, B.B.Cement production is excessive energy intensive, responsible for depletion of natural layers and high carbon foot print. Thus search for an environmentally benign cement substitute still is an on-going process. Fly ash is a well-established concrete admixture enhancing the strength, durability and micro-structural properties. As well as it is a good reagent to sequester atmospheric carbon dioxide. Concretes prepared through part replacement of cement by carbonated fly ash demonstrate good resistance against chloride, acid and sulfate attack. In the present research mineralogical study of CFC (Carbonated Fly ash concrete) has been conducted through XRD analysis. XRD of control concrete (CC) and fly ash concrete (FC) have also been carried out to study the comparative distributions of mineral crystallites present in concretes. The tests have been conducted in the concrete specimens cured in water for 28 days and 90 days to study the effect of hydration and extent of pozzolanic reaction on the mineralogical composition. Two replacement levels of 25 and 40% were considered for experimentation. The qualitative XRD investigation yielded a higher intensity of CaCO3 in the concretes prepared using Carbonated Fly ash. The presence of CaCO3 helped the concretes in developed chemical resistances dense and improved microstructure. The thermogravimetric analysis further confirmed the presence of higher Carbonates in the CFC specimens. © Springer Nature Singapore Pte Ltd. 2019.Item Simulink-Based Comparative Study and Selection of a Controller for a Waist-Assistive Exoskeleton(Springer Science and Business Media Deutschland GmbH, 2024) Thomas, M.J.; Mohanta, J.; Sahoo, S.; Santhakumar, S.This paper describes the conceptual design and comparative simulation study of three controller strategies—Proportional Integral Derivative (PID), PD-based Computed Torque Control and PD-based Sliding Mode Control (SMC) for a waist-assistive exoskeleton. The exoskeleton is modelled in Simulink, and its joint control is simulated for a predefined desired trajectory. The motor, joint and link parameters are incorporated into the Simulink model to match the properties and evaluate the performance similar to the real-time system. In addition, MSC ADAMS-based simulation study is also performed to validate the dynamic model of the exoskeleton. The preliminary study indicates that the SMC controller shows better tracking accuracy than the other two strategies. The proposed exoskeleton is designed to reduce the effort taken by the user during regular sit-to-stand and weight-lifting operations. It is intended to lower the strain the lumbar muscles take during standing and lifting operations over the long run. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Acid, alkali and chloride resistance of high volume fly ash concrete(Indian Society for Education and Environment indjst@gmail.com, 2015) Sahoo, S.; Das, B.B.; Rath, A.K.; Kar, B.B.Objectives: To find variation in compressive strength and mass of high volume fly ash concrete samples subjected to different chemical solutions of sodium chloride, sodium sulphate and sulphuric acid. Methods: A total of 900 numbers of cubes were cast and cured with four levels of curing period of 28, 56, 90 and 120 days. After certain duration of curing period, specific numbers (60) of cubes were submerged each in 5 percent sodium sulphate solution (Na2SO4), 5 percent sodium chloride solution (NaCl) and 1percent of sulphuric acid solution (H2SO4) separately in chemical exposure containers for an exposure period of 30, 60, 90 and 120 days. Findings: Investigations with respect to acid, alkali and chloride resistance were carried out on high volume fly ash concrete, HFC (40 percent replacement with cement), low volume fly ash concrete, LFC (25 percent replacement with cement) and their performances against control concrete (NC) is presented in this paper. Their performance was measured with respect to the loss in compressive strength and weight of the concrete cubes over the period of exposure time. It is found that the resistance of control concrete to all the three chemical attack is better only up to 28 days of water curing. At 56 days of water curing LFC shows better resistance against the control and HFC. However, with prolonged water curing of cubes of 90 days and more, HFC has consistently shown highest resistance; whereas the control concrete faced a great loss in strength.Item Acid, alkali, and chloride resistance of concrete composed of low-carbonated fly ash(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2017) Sahoo, S.; Das, B.B.; Mohammed Mustakim, S.This research investigates the effect of carbonated fly ash inclusion in concrete as partial replacement of cement on the durability performance when exposed to salt, sulfate, and acid solution. The effect of chemical exposure periods (30, 60, 90, and 120 days) on compressive strength and weight of concrete with low volume (25%) replacement of cement was investigated for various water curing ages (28, 56, 90, and 180 days). A comparative assessment with low volume (25% cement replacement) fly ash concrete and control concrete was also conducted. It was observed from the results that low volume carbonated fly ash concrete demonstrated a significant increase in resistance to loss in compressive strength and weight against salt, sulfate, and acid attack. Gray relation-based analysis was performed to determine suitable parameters for simultaneous minimization of strength loss and weight loss under chemical exposure. It can be recommended that, due to its cost-effectiveness, easy processing, and environmental friendly nature, carbonated fly ash can be adopted in construction as a partial replacement of cement in concrete. © 2016 American Society of Civil Engineers.