Browsing by Author "Sumukh, E.P."

Now showing 1 - 7 of 7

A Review on the Properties of Steel-Concrete Interface and Characterization Methods
(Springer Science and Business Media Deutschland GmbH info@springer-sbm.com, 2021) Sumukh, E.P.; Goudar, S.K.; Das, B.B.
The Steel-Concrete interface (SCI) is usually regarded as the weakest region, which influences both mechanical properties and durability of reinforced concrete structures. Several researchers have well explored and defined the importance of SCI on the service life of the reinforced concrete structures as it directly affects the durability. The primary objective of this paper is to report and compare a variety of published findings and microstructural analysis on the SCI in one place which appears in reinforced concrete. The information available on the occurrence, formation, properties, various characterizing and analysing techniques of SCI are reviewed for a better understanding of microstructural properties of SCI on the hardened and durability properties of reinforced concrete. It was found that the SCI exhibits significant spatial inhomogeneity along and around as well as perpendicular to the reinforcing steel. Significant factors like quantification of porosity, porous zone thickness and actions that affect the properties of SCI like wall effect, bleeding, settlement and segregation of fresh concrete which were favourable to both initiation and propagation of corrosion are described in this paper. The influence of w/c ratio, hydration age, steel orientation and mineral admixtures on the distribution profiles of hydration products and Engineering properties of SCI is also discussed. Â© 2021, Springer Nature Singapore Pte Ltd.
Effect of Iron Ore and Copper Ore Tailings on Engineering Properties and Hydration Products of Sustainable Cement Mortar
(ASTM International, 2024) Sumukh, E.P.; Das, B.B.; Barbhuiya, S.
The prohibition of river sand mining has drawn the attention of researchers in finding practicable alternatives. In the approach of finding these alternatives, it is essential to ensure minimal or zero impairment to the ecological balance, which can be mainly attained by making use of industrial waste/byproducts. The wastes from the mining industry are the major contributors in causing impairment to the environment, and their influence on the stability of mortars on using as fine aggregates needs to be systematically investigated with the view of long-term performance concerns. Thus, the present study explores the applicability of mine tailings and finding the optimum dosage in cement mortars by investigating the engineering properties and microstructure development with the aid of qualitative and quantitative analysis associated with hydration products. The studies confirm that the increased consumption of portlandite for secondary hydration reactions followed by the additional formation of calcium silicate hydrate (CSH) and calcium aluminum silicate hydrate (CASH) phases in mine tailing-based mortars helped in achieving a quality microstructure. These additional formations of CSH and CASH phases are also confirmed through Fourier transform infrared spectroscopy by identifying the shift of Si-O-Si stretching vibration bands toward a lower wavenumber. The lowering of calcium/silicate atomic ratio and increased formation of mineralogical compounds related to CSH and CASH in x-ray diffraction patterns also confirms the same. Gismondine, chabazite, and hillebrandite are the additional phases formed and found to take part in refining the pore structure. This enhanced performance of mine tailing mortars was also verified with the aid of a modified Andreasen and Andersen particle packing model. The formation of high-quality microstructure is reflected in the hardened properties of optimized cement mortar in the proportion of 20 % for iron ore tailing and 30 % for copper ore tailing. © © 2024 by ASTM International.
IMPLICATION OF HIGH-VOLUME MINERAL ADMIXTURE ON MECHANICAL PROPERTIES AND MICROSTRUCTURE AT STEEL-CONCRETE INTERFACE
(Associated Cement Companies Ltd., 2023) Goudar, S.K.; Sumukh, E.P.; Das, B.B.
The existence of a non-homogeneous unique zone in concrete along the periphery of steel surface is being referred as steel-concrete interface (SCI). The interface between steel and concrete exhibits a porous zone, with a thickness measuring several micrometers. This porous zone thickness around SCI plays a crucial role in influencing bond strength, durability, and is a significant parameter used in service life prediction models for reinforced concrete structures. The value of porous zone thickness around SCI is being assumed and adopted without any practical studies in service life prediction models as well as in reinforced concrete mesoscale structure modelling. In the present study, porous zone thickness was experimentally measured through obtaining backscattered electron images around SCI. Gray scale-based thresholding technique was employed to ascertain the porous zone thickness (PZT) around SCI. Furthermore, the influence of incorporating ground granulated blast furnace slag (GGBS) in high-volume on the interfacial transition zone (ITZ) between steel reinforcement bars and the surrounding concrete was investigated. It was observed that porous zone thickness around SCI varies in every other point along the periphery of reinforcement bar. The pozzolanic reaction in high volume GGBS concrete resulted in a substantial decrease of porous zone thickness (PZT) and reduced the accumulation of Portlandite around SCI with the progress in curing age. The factors contributing to the enhanced ultimate bond strength of high volume GGBS concrete compared to control concrete are the decrease in the Porous Zone Thickness (PZT) along with the reduced Ca/Si ratio around the SCI. © 2023, Associated Cement Companies Ltd.. All rights reserved.
Influence Of Marine Environment Exposure On The Engineering Properties Of Steel-concrete Interface
(Bentham Science Publishers, 2022) Goudar, S.K.; Sumukh, E.P.; Das, B.B.
Aims: A detailed and reformed service life prediction model needs to be developed by considering the non-uniform distribution of the porous zone and the non-uniform distribution of the corrosion products layer. Background: The microstructure of the steel-concrete interface (SCI) plays an important role in corrosion initiation and concrete cover cracking. The porous zone around SCI is one of the vital engineering properties that influence the service life of corroding reinforced concrete structures in service life prediction models. Objective: The SCI properties are sensitive to the sample preparation technique of reinforced concrete (RC) samples for studying with the aid of scanning electron microscopy (SEM). A simple step-wise sample preparation technique of RC samples for SEM analysis is proposed where there is minimal damage to the properties of SCI. The development, distribution, and propagation of corrosion products at SCI are investigated for RC samples exposed to the marine environment for different exposure periods. The service life of RC structures was assessed through experimentally determined porous zone thickness (PZT) values. Assuming a uniform and constant value of PZT and uniform distribution of corrosion products around SCI might lead to variation or misinterpretation of the service life of structures. The same is explored in the present study. Methods: In this research investigation, backscattered electron images were obtained for the analysis of porous zone thickness around SCI. The distribution and propagation of corrosion products around SCI were investigated for different mineral admixed reinforced concrete samples exposed to the marine environment. Also, porous zone thickness values were used experimentally measured, and the time from corrosion initiation to corrosion cracking was estimated using a service life prediction model. Results: Results show that porous zone thickness is not uniform around SCI. Once the corrosion is initiated, the corrosion products accumulate in the SCI's porous region. Further, the non-uniform porous zone thickness directly influenced the non-uniform distribution of corrosion products. Assuming a constant or uniform porous zone thickness and uniform distribution of corrosion products around SCI leads to misinterpretation of the service life of corroding reinforced concrete structures. Conclusion: The porous zone thickness values around the steel-concrete interface and corrosion current density play an important role in predicting the service life of reinforced concrete structures exposed to the marine environment. © 2022 Goudar et al.
Predicting the Service Life of Reinforced Concrete by Incorporating the Experimentally Determined Properties of Steelâ€“Concrete Interface and Corrosion
(Springer Science and Business Media Deutschland GmbH, 2021) Sumukh, E.P.; Goudar, S.K.; Das, B.B.
Service life of a reinforced concrete structure depends on its durability in aggressive exposure conditions. In the case of reinforced concrete structures, the phenomenon that directly affects its durability is corrosion of rebar, which has direct influence on the residual service life. Corrosion in reinforced concrete basically initiates at its weakest zone called steelâ€“concrete interface due to its porous nature. The extent of this porous zone is being represented in terms of Porous zone thickness which has been extensively reported by various researchers. This porous zone thickness is one of the key influencing factors in the prediction of residual service life of the reinforced concrete structure. Several mathematical models were proposed by various researchers to estimate the time required for cover cracking of concrete due to rebar corrosion by assuming different values of porous zone thickness (PZT) without any systematic experimental investigation. Assuming a steady value of PZT for all kinds of concrete without any practical justification will misinterpret the predicted residual service life. In the present work, an effort has been made to evaluate an existing analytical model to predict the time to concrete cover cracking by incorporating the experimentally obtained and published data on porous zone thickness. It was found that the porous zone thickness and rate of corrosion have a major role in evaluating the residual service life of reinforced concrete structures. Â© 2021, Springer Nature Singapore Pte Ltd.
Resistance to acid, alkali, chloride, and carbonation in ternary blended high-volume mineral admixed concrete
(Taylor and Francis Ltd., 2024) Das, B.B.; Black, L.; Barbhuiya, S.; Snehal, K.; Sumukh, E.P.
The World Bank study predicts that 4 °C warming will bring high temperatures, sea-level rise, and saltwater intrusion to coastal areas, damaging coastal concrete structures. Increased CO2 from industrialization exacerbates this, necessitating durable, low-carbon concrete. Combined use of fly ash (FA) and ground granulated blast furnace slag (GGBFS) as high-volume OPC replacements boosts performance while reducing concrete’s carbon footprint. In this perspective current study examines the durability of concrete against aggressive agents (H2SO4, MgSO4, NaCl, and CO2) causing premature deterioration of concrete structures. Initially, three cost-effective sustainable concrete mix designs were developed, incorporating 50% replacement of OPC with locally available supplementary cementitious materials, specifically FA and GGBFS. These mixes were then evaluated for their mechanical and durability performances. The impact of aggressive ions (SO42−, Cl−, and CO32−) was studied by examining the changes in mechanical performance and phase assemblages. Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) techniques were used to estimate the phase compositions. Ternary blended concrete having 50% OPC+ 30% GGBFS + 20% FA exhibited optimal synergistic performance, enhancing pozzolanic and hydraulic reactions for better resistance to harmful ions. The sorptivity test confirmed that as the GGBFS content increased, the sorption rate decreased, indicating the higher reactive nature of GGBFS to that of FA. Deleterious compounds formed due to the action of SO42-, Cl-, and CO32- were identified to be ettringite (Ca6Al2(SO4)3(OH)12.32H2O, AFt) and gypsum (CaSO4.2H2O, Gy), Friedel’s salt (Ca4Al2(OH)12Cl2.4H2O, Fs) and polymorphs of calcium carbonate (CaCO3), respectively through TG mass loss curve. These results were corroborated by FTIR analysis, which showed predominant characteristic bands at 662 cm−1 for SO42−, 459 cm−1 for Mg–O stretching, 790 cm−1 for Al–OH bending, and 1431-1443 cm−1 for C–O, confirming the presence of the deleterious compounds. © 2024 Informa UK Limited, trading as Taylor & Francis Group.
Synergy of Hydration and Microstructural Properties of Sustainable Cement Mortar Supplemented with Industrial By-Products
(Springer Science and Business Media Deutschland GmbH, 2024) Sumukh, E.P.; Das, B.B.; Barbhuiya, S.
The present research assists in resolving the issues allied with the disposal of industrial solid wastes/industrial by-products (IBPs) by developing sustainable IBPs based cement mortars. The applicability of IBPs as a feasible alternative to river sand in cement mortar has been evaluated by investigating the synergy among the ingredients, resulting engineering properties and microstructural developments at early and late curing ages. The study could effectively substitute 30% volume of river sand with bottom ash and 50% in the case of slag sand mortars. The experimental outcomes disclose that the practice of IBPs as fine aggregate enhances the engineering properties of mortar and the optimum replacement level lies at 10% and 40% usage of bottom ash and slag sand, respectively. The advanced characterization studies and particle packing density illustrate the refinement of pores by void filing action and accumulation of additional hydration products through secondary hydration reactions. The consumption of portlandite followed by increased hydration products formation observed through thermogravimetric analysis, X-ray diffraction analysis and energy dispersive X-ray spectroscopy that confirmed the contribution of finer fractions of IBPs to secondary hydration reactions. This constructive development was also observed from the lowering of wavenumber corresponding to Si–O–Si/Al vibration bands in Fourier transform infrared spectroscopy spectra. The improved microstructure resulted in enhancing the compressive strength by 9.01% and 18.18% in optimized bottom ash and slag sand mortars, respectively at the curing age of 120 days. Similarly, the water absorption reduced by 1.03% and 1.24% in bottom ash and slag sand mortars, respectively. © The Author(s), under exclusive licence to the Iran University of Science and Technology 2024.