Faculty Publications
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Item Durability studies of steel fibre reinforced concrete(Springer, 2019) Yadav, S.; Das, B.B.; Goudar, S.K.In the present investigation, the effect of different dosage of steel fibres on bond strength between steel and concrete in reinforced concrete was investigated. As a part of durability study, the combined effect of marine environment and varying levels of pH on the ultimate bond strength retention and compressive strength retention of steel fibre reinforced concrete was also investigated. Durability studies were carried out by exposing the 28 days cured cubical specimens into marine environment having different pH levels (1, 4, 7, 10 and 13). The marine environment was simulated in the laboratory by adding 3.5% NaCl to the tap water. Designed quantity of sulphuric acid was added to salt solution to maintain pH of 1 and 4 in marine environment. Similarly, designed quantity of sodium hydroxide was added to the salt solution to maintain pH of 10 and 13 in marine environment. The specimens were exposed for the durations of 60 and 90 days. The resistance of concrete to marine environment with varying pH was measured through compressive strength retention and ultimate bond strength retention in steel fibre reinforced concrete. The addition steel fibres reduced workability of concrete, especially 1.5% of steel fibres yielded considerably low slump value. The ultimate bond strength and compressive strength values increased due to the addition of steel fibres. The pH of the marine environment has a significant influence on the compressive strength retention and bond strength retention. Exposure to marine environment with pH 1 underwent severe loss in compressive strength and ultimate bond strength with very low strength retention values. However, exposure to marine environment with pH 10 and 13 had minimal strength losses with higher values of compressive strength and ultimate bond strength retention. The alkaline nature of marine environment was not susceptible to strength reduction when compared to neutral (pH 7) and acidic (pH 1) marine environment. The steel fibre reinforced concrete performed better in acidic marine environment compared to control concrete without steel fibres. © Springer Nature Singapore Pte Ltd. 2019.Item Performance of concrete structures in the marine environment of Karnataka, India(2003) Devadas Bhat, S.; Samaga, B.R.Well-made concrete often survives better than might otherwise be expected, simply because of its impermeability and its ability to withstand the ingress of corrosive materials. The less the surplus voids the greater is the resistance to deterioration. Corrosion of steel is a multibillion-dollar problem worldwide. However, there are many structures, which show early deterioration, namely those exposed to aggressive environments. In the past and even at present times, too much emphasis is placed on concrete compressive strength rather than on environmental factors, which are known to affect concrete durability. This is one of the main reasons for serious deterioration of concrete structures that is prevalent today. The long-term behaviour of concrete structures has shown that their main cause of distress is reinforcement corrosion. One of the most aggressive exposure conditions for concrete is the marine environment In these condition chloride penetration and chloride induced reinforcement corrosion rates can be very high, often leading to a reduced service life. This paper describes a series of case studies of different types of concrete structures, subjected to marine environment in the West-Coast of Karnataka (INDIA), that have suffered extensive deterioration due to corrosion.Item Corrosion behavior of novel AA1050/ZnO surface composite: A potential material for ship hull(Elsevier B.V., 2020) Bajakke, P.A.; Vinayak, V.R.; Jambagi, S.C.; Deshpande, A.S.Friction stir processing is one of the effective surface treatments which was employed to process the AA1050 sheets in bare and reinforced condition. The primary objective of the investigation was to expand the applications of AA1050 as a ship hull element in shipbuilding with the least corrosion rate to withstand the harsh marine environment. The base material processed with a rotational speed of 1200 rpm resulted in the highest corrosion rate of 0.173622 mpy. The formation of Al-Fe intermetallic phases was responsible for pitting corrosion. Further, processing by embedding zinc oxide with a rotational speed of 1000 rpm exhibited ~6.68 times improvement in corrosion resistance compared to as-received material. The corrosion rate was found to be 0.003390 mpy. The Al2O3 passive film hinders the initiation and propagation of pits. This study coins a novel composite material and future investigations are emphasized on the same lines. © 2020 Elsevier B.V.Item An experimental investigation on mitigating cracks and augmenting the endurance of concrete structures in marine environment by bio-mortar immobilised with halophilic bacteria(Elsevier Ltd, 2024) Baby, B.; Palanisamy, T.In coastal areas, built structures encounter hostile conditions and forces that can cause them to deteriorate over time owing to saltwater exposure, tidal forces, reinforcement corrosion, and freeze–thaw cycles. Early age cracks in such structures accelerate the rate of deterioration, and the current research focuses on alleviating such threats. This paper evaluates the performance of a self-healing mortar made by encapsulating expanded perlite with the bacterium Halobacillus Halophilus MCC2188. Mortar cube specimens of size 70.6 mm × 70.6 mm× 70.6 mm were prepared with cement: fine aggregate in 1:3 ratios. A 10% volume of the fine aggregate fraction was substituted with the expanded perlite immobilised with bacterial spores and nutrients. The expanded perlite aggregates were coated with sodium silicate and cement solution to protect the spores from the nonconducive environment. The specimens were subjected to fully and partially submerged marine water curing. The mechanical properties and self-healing potential were evaluated, and the precipitated polymorphs in completely healed cracks were identified and examined by characterisation techniques such as XRD, FEGSEM, FTIR, and TGA-DTG. The marine bacterium under investigation can tolerate the high salt concentrations commonly found in seawater and saline marshy soil and produce calcite through the metabolism of organic compounds, making it a suitable microorganism for self-healing applications. Crack widths of up to 0.84 mm and 92.79% average strength recovery were achieved in 56 days post-cracking, and the pace of healing was quicker in partially submerged curing conditions. The results showed improved self-healing, strength regain and mechanical strength and proved to be an efficient tool for enhancing the endurance of biomortar in severe marine exposure conditions. © 2024 Elsevier LtdItem Investigation on the Hardness of Al6061 Alloys: Implications of Seawater Corrosion(Springer, 2024) Begum, Y.; Doddamani, S.This study aims to investigate the impact of seawater corrosion on the hardness of Al-Mg-Si alloys, providing insights into the mechanical alterations induced by exposure to corrosive marine environments. Al-Mg-Si alloys are widely used in marine environments because of their high strength-to-weight ratio and excellent corrosion resistance. However, exposure to seawater can lead to corrosion, which can alter their mechanical properties, including hardness. In this study, Al6061 alloy specimens were exposed to seawater for different periods (3–30 days), and their hardness was measured using Vickers hardness testing. The corrosion rate was determined by weight loss analysis. The results showed that the corrosion rate of Al6061 alloys increased with increased exposure time in seawater, up to 20%. The hardness versus corrosion rate plot analysis indicates an inverse relationship, with scatter points aligning well with a linear regression model. The Vickers' hardness of the samples decreased as the corrosion rate increased. This hardness decline in Al6061 alloys under escalating corrosion rates is attributed to material loss, heightened porosity, and microstructural transformations arising from corrosion product formation. Comprehensive corrosion micrographs unveiled advanced corrosion stages, marked by dynamic pit and crack expansion, oxide layer degradation, pit coalescence, and emergence of distinct corrosion patterns. © The Minerals, Metals & Materials Society 2024.Item Exploring the protection of spray-pyrolysed tungsten oxide hydrophobic coating on stainless steel in a marine environment(Springer, 2024) Gautam, V.; Praveen, L.L.; Vardhan, R.V.; Mandal, S.Tremendous potential in the field of anti-biofouling coatings to prevent stainless steel (SS)-based underwater pipelines, sea vessels and other marine structures have been recognized to protect from biofouling, which is often initiated by algae attachment over the surface. In this work, hydrophobicity in spray-pyrolysed tungsten oxide (TO) coating on SS-316 substrate has been reported for the first time, via post-processing treatment using octadecyltrimethoxysilane (ODTMS) to induce self-assembled monolayer (SAM). Initially, structural and vibrational characteristics of ODTMS and ODTMS-treated TO (OTO) coating on SS were analysed using X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopies. OTO-coating depicted a water contact angle (WCA) of 121°, revealing its hydrophobic nature, with further affirmation from X-ray photoelectron spectroscopy (XPS). Durability of the TO-coating was explored using the scratch hardness (Hs) test at different loading conditions (5, 10 and 15 N). Biofouling study was conducted by culturing blue-green algae (BGA, Phormidium sp.) in an in-house laboratory setup for 40 days, using seawater (collected from the Arabian Sea, Karnataka). The SS, TO- and OTO-coatings were immersed for 14 days in a controlled sea-water environment in the laboratory with the presence of BGA. A comparative study on the areal-algae attachment was keenly analysed over SS-, TO- and OTO-coatings. This work can be projected as a promising application providing multi-dimensional solutions in creating scratch-resistant and anti-biofouling coatings on SS in the shipbuilding industry. © Indian Academy of Sciences 2024.Item Influence of weld parameters on the tribocorrosion behaviour of friction stir welded AA5052 in the marine environment(Elsevier Ltd, 2025) Anantharam, G.S.; Bhole, K.B.; Kuriachen, B.; Arya, S.B.The study involves tribocorrosive investigation of FSW-AA5052 formed at tool-speeds of 800, 1000, and 1200 rpm and welding-speeds of 60, 80, and 100 mm/min, for which Pin-on-disc tests in conjunction with open-circuit-potential and potentiodynamic-polarization techniques were utilised. For microstructures EBSD, Optical images and XRD were taken. Results revealed that cast (?1.212 V; 332.43 ?m/year), 800 rpm (?1.213 V; 433.51 ?m/year) and 1000 rpm (-1.236 V; 227.45?m/year) welded samples showed better performance than all the 1200 rpm welded samples. Frictional characteristics of 800 rpm (CoF-1.28) and 1000 rpm (CoF-1.32) samples were better than other samples due to uniform and stable passivation. Elemental analysis showed Oxides and Chlorides of Al and Mg formed over the worn surfaces. © 2025 Elsevier Ltd