Faculty Publications
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Item Behavior of Alloying Elements during Electro-Slag Remelting of Ultrahigh Strength Steel(2012) Bandyopadhyay, T.R.; Rao, P.K; Prabhu, N.The paper deals with the behavior of principal constituents of an ultrahigh strength steels during ESR. The multiple analyses show no significant variation in the concentrations of silicon, manganese, vanadium, molybdenum, sulphur and phosphorus while concentrations of carbon, chromium, aluminium and titanium in the ESR ingot are found to be within the range of ± 0.01, ± 0.12, ± 0.008 and ± 0.01% respectively. Silicon and manganese show a loss of 0- 55 and 2-13% respectively whereas the degree of desulphurization is in the range of 0 (in Ar shield) to 52 (in air). The lower carbon and chromium content of the electrode than the aimed value can be corrected by adding ferrochromium in-situ during ESR. The recovery of carbon from FeCr was nearly 100% in most of the melts while the recovery of chromium varied over a fairly wide range. The distributions of carbon and chromium are also uniform along the height and width of ESR ingots. The recovery of the inoculant titanium was relatively low at the bottom of the ingot and it increases with height and reached a constant value above 100-150 mm height. For the same addition of titanium, its recovery decreases during ESR with argon shielding. © Metallurgical and Mining Industry.Item Recuring studies on concretes subjected to elevated temperatures and suddenly cooled by water quenching(Multi-Science Publishing Co. Ltd, 2015) Yaragal, S.C.; Kittur, M.M.; Babu Narayan, K.S.Concrete is found to undergo degradation when subjected to elevated temperatures during an accidental event, such as fire and lose substantial amount of its original strength. The loss of strength in concrete is mainly attributed to the decomposition of Calcium Silicate Hydrate (C-S-H) and release of chemically bound water, which begins when the exposure temperature exceeds 500°C. When such a concrete is supplied with water and allowed to recure, it is found to recover substantial amount of its lost strength. This work is carried out to investigate the effect of recuring on strength recovery of un-blended and blended concrete specimen (100 mm cubes) subjected to elevated temperatures from 400°C to 700°C, in steps of 100°C, for a retention period of two hours at the designated temperatures. The concrete cubes immediately after exposure were subjected to thermal shock by quenching them in water, and then temperature of thermally shocked concrete is allowed to cool to room temperature. The cooled specimen were then recured in water for 1, 3, 7, 14, 21, 28, 56 days and tested for compressive strength recovery. These studies were carried out for Portland Cement (PC) based concrete and Portland & Granulated Blast Furnace Slag (70% PC + 30% GGBS) based concrete (blended concrete), and some interesting results are presented and discussed in this paper. © 2015, Multi-Science Publishing Co. Ltd. All rights reserved.Item Air-cured Alkali activated binders for concrete pavements(Chinese Society of Pavement Engineering, 2015) Palankar, N.; Ravi Shankar, A.U.; Mithun, B.M.The present study focuses on the possibility of use of alkali activatedbinders for use in concrete pavements. Alkali Activated Slag Concrete (AASC) and Alkali Activated Slag Fly ash Concrete (AASFC) are prepared and the properties are compared with Ordinary Portland Cement Concrete (OPCC). The Ground Granulated Blast FurnaceSlag (GGBFS) and Fly Ash (FA) are blended in the ratios 100:0, 75:25, 50:50 and 25:75 as binder and activated using strong alkaline solution. Trial mixes are carried out to identify the optimal Activator Modulus (Ms) for each combination of GGBFS and FA. The mix design for the optimal activator modulus is optimised to achieve sufficient strength for Pavement Quality Concrete (PQC) and the fresh and mechanical properties are studied in detail. The results indicate the properties of AASC and AASFC are similar or slightly better than conventional OPCC and satisfy the minimum strength requirements for concrete pavements. The application of alkali activated binders will minimise the environmental hazards occurring from augmented OPC production, along with effective utilisation of industrial waste materials and conservation of natural resources. © Chinese Society of Pavement Engineering.Item Performance of alkali activated slag concrete mixes incorporating copper slag as fine aggregate(Elsevier Ltd, 2016) Mithun, B.M.; Narasimhan, M.C.In this present study, copper slag (CS) is proposed as an alternative to river sand as fine aggregate in alkali-activated slag concrete (AASC) mixes. The relative performance of alkali activated slag concrete mixes with CS as fine aggregate is compared to conventional Ordinary Portland Cement concrete (OPCC) mix in terms of their workability, strength and durability parameters. The results indicate that, AASC mixes with CS, as a replacement to sand upto 100% (by volume), show no marked loss in strength characteristics. AASC mixes with either sand or CS possess similar modulus of elasticity, lower total porosity, lesser water absorption and reduced chloride ion penetration as compared to OPCC. Strength-retention characteristics of AASC mixes with sand/CS on exposure to sulphate and acid-rich environment are also studied. Use of AASC mixes for structural application reduces carbon footprint, decreases water consumption and cost. Use of CS as fine aggregate reduces river sand consumption as an added benefit. © 2015 Elsevier Ltd. All rights reserved.Item Durability studies on eco-friendly concrete mixes incorporating steel slag as coarse aggregates(Elsevier Ltd, 2016) Palankar, N.; Ravi Shankar, A.U.; Mithun, B.M.The present study discusses the durability performance of alkali activated concrete mixes containing steel slag as coarse aggregates. Steel slag aggregates, a waste product obtained from iron and steel industry are incorporated as coarse aggregates in alkali activated slag concrete (AASC) and alkali activated slag fly ash concrete (AASFC) by replacing traditional natural aggregates. The mix design for AASC and AASFC mixes are optimised to obtain sufficient strength for structural purposes and then steel slag coarse aggregates are incorporated at different replacement levels (0%, 50% and 100% by volume of total coarse aggregate content). Durability properties such as long term ageing performance, water absorption, volume of permeable voids, resistance to sulphuric acid attack and resistance to magnesium sulphate attack are studied in detail and compared with conventional Ordinary Portland Cement Concrete (OPCC). The ecological and economical analysis of concrete mixes is also carried out. It was found that the AASC and AASFC mixes displayed better durability performance as compared to OPCC. The inclusion of steel slag aggregates slightly reduced the durability performance of AASC and AASFC mixes. The AASC and AASFC with steel slag aggregates displayed lower energy requirement and lower production cost as compared to OPCC, thus proving it to be eco-friendly. © 2016 Elsevier Ltd. All rights reserved.Item Investigations on Alkali-Activated Slag/Fly Ash Concrete with steel slag coarse aggregate for pavement structures(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2017) Palankar, N.; Ravi Shankar, A.U.; Mithun, B.M.The present investigation is conducted to evaluate the effect of steel slag coarse aggregates on mechanical properties and fatigue behaviour of Alkali-Activated Slag Fly Ash Concrete (AASFC) mixes. AASFC mixes were prepared with steel slag coarse aggregates by replacing natural coarse aggregates at various replacement levels (0, 25, 50, 75 and 100% by volume). Various mechanical properties and fatigue performance were tested and compared with conventional Portland concrete. The incorporation of steel slag aggregates resulted in decrease in mechanical strength of AASFC mixes. The fatigue lives of AASFC mixes containing steel slag were found to be lower than AASFC with natural coarse aggregates. Two-parameter Weibull distribution was used for statistical analysis of fatigue data and it was observed that the fatigue data of concrete mixes can be approximately modelled using Weibull distribution. Steel slag aggregates reported acceptable performance in AASFC mixes for its use in pavement quality concrete. © 2015 Informa UK Limited, trading as Taylor & Francis Group.Item Enhancement of the properties of fly ash based geopolymer paste by incorporating ground granulated blast furnace slag(Elsevier Ltd, 2017) Saha, S.; C, C.Research efforts have been made continuously to establish fly ash based geopolymer as an alternative binder material for the production of fresh concrete because production of Ordinary Portland Cement degrades the environment by huge emissions of carbon-di-oxide and also by consuming lot of natural resources. But most of the study reveals, fly ash based geopolymer paste needs more time to get set when it is cured at ambient temperature. As a result, it is quite impractical to use fly ash based geopolymer paste as an alternative to Ordinary Portland Cement in faster construction. In this study, an effort has been made to enhance the properties of fly ash based geopolymer paste by incorporating ground granulated blast furnace slag at various percentage levels. Microstructure of the geopolymer paste is studied using Scanning Electron Microscopy. Result of this investigation shows that significant improvement on setting time and compressive strength can be obtained by adding ground granulated blast furnace slag in the mixes. © 2017 Elsevier LtdItem Influence of Granulated Blast Furnace Slag and Cement on the Strength Properties of Lithomargic Clay(Springer India sanjiv.goswami@springer.co.in, 2017) C. Sekhar, D.C.; Nayak, S.; Preetham, H.K.Utilizing industrial byproducts in soil stabilization benefits the economic, environmental and social benefits. Granulated blast furnace slag is a byproduct of iron and steel industry having oxides similar to that of cement but in different proportions. This study describes experimental results achieved by the use of granulated blast furnace slag (GBFS) and cement in stabilizing lithomargic clay for geotechnical applications. Soil was replaced by GBFS in percentages of 10, 15, 20, 25, 30, 35, 40, 45, 50% and cement of 2, 4, 6, and 8% by dry weight of soil is added. Various experimental studies like specific gravity, Atterberg limits, compaction, UCS, CBR and triaxial compression test, were performed on samples to understand the effect of these mixes on their few index and strength properties. The study also includes an investigation on a combination of optimum percentage of GBFS with varying percentage of cement and lime on their shear parameters. The study result shows significant improvement in the strength properties of the mixes. Hence it can be concluded that lithomargic clay stabilized with GBFS and cement/lime satisfy the strength requisite to be employed in the numerous geotechnical applications. © 2017, Indian Geotechnical Society.Item Eco-concrete for sustainability: utilizing aluminium dross and iron slag as partial replacement materials(Springer Verlag, 2017) Javali, S.; Chandrashekar, A.R.; Naganna, S.R.; Manu, D.S.; Hiremath, P.N.; Preethi, H.G.; Vinod Kumar, N.Emphasis on utilizing the industrial waste/discarded materials can be brought about by discovering innovative methods of disposal. One such a way of waste disposal can be through utilizing them in concrete production as a filler material or pozzolana. In this regard, the present study proposes to use the aluminium dross and granular iron slag as partial replacement materials for cement and natural sand, respectively, to develop eco-concrete. Nine mixes were produced with different proportions of cement, aluminium dross, sand and granular iron slag content. The aluminium dross was replaced at 5, 10, 15 and 20% of the weight of the cement. Initially, the optimal substitution percentage of aluminium dross was found without the substitution of iron slag based on the strength results. Later, by adopting the optimal aluminium dross percentage with cement, the granular iron slag was partially substituted at 10, 20, 30 and 40% of natural sand to find the overall optimal blend. The strength and durability properties of the M40 grade concrete employing these two admixture combinations were analysed. It was noticed that the strength and durability properties of the eco-concrete produced by incorporating aluminium dross ?5% and iron slag ?20% were comparable to that of conventional concrete. Furthermore, from the toxicity analysis, it was seen that the leaching of heavy and trace elements from the eco-concrete was negligibly small and within the limits. In near future, the cost-effective, eco-friendly materials and technologies can be opted as a perpetual strategy to overcome severe material shortages for resource conservation and economy. © 2017, Springer-Verlag GmbH Germany.Item Utilization of granulated blast furnace slag and cement in the manufacture of compressed stabilized earth blocks(Elsevier Ltd, 2018) C. Sekhar, D.; Nayak, S.This study involves the investigation on utilization of granulated blast furnace slag (GBFS) and cement in the manufacture of compressed stabilized earth blocks (CSEB). Two locally available soils from Dakshina Kannada district, Karnataka, India were tested for their index and strength properties with replacement of granulated blast furnace slag (GBFS). An optimum percentage of replacement of GBFS was established and then varying percentages of cement was added for the production of compressed stabilized earth blocks (CSEBs). This stabilized soil was used for the manufacture of blocks of size 305 mm × 143 mm × 105 mm. All the blocks were cast to a target density, followed by the curing for 28 days. The blocks were subjected to compression test and water absorption test according to Indian Standard (IS) specifications. The test results showed that the CSEBs prepared with GBFS and cement can be utilized in masonry for load bearing wall construction. A small percentage of cement is sufficient for manufacturing the CSEBs when optimum GBFS content is replaced with that of soil, thereby reducing the energy consumption. © 2018 Elsevier Ltd