Faculty Publications
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Item Virgin and waste polymer incorporated concrete mixes for enhanced neutron radiation shielding characteristics(Elsevier, 2018) Malkapur, S.M.; Narasimhan, M.C.Several attempts have been made in the past to develop newer concrete mixes with enhanced neutron radiation shielding characteristics. The composition of the concrete mixes becomes very important in this context, and it is extensively reported that the hydrogen content in the hydrated concrete mixes is one of the important constituents determining the neutron radiation shielding capabilities of the mixes. It is professed that higher the hydrogen content, better is the neutron radiation shielding. The use of different types of hydrogen sources in the past such as hydrogenous mineral aggregates and liquid polymers, and polymer impregnation, has been discussed. The feasibility issues and concerns while using virgin and waste pulverized high-density polyethylene (HDPE) polymeric materials as partial replacement to fine aggregates for making concrete mixes with enhanced neutron radiation shielding characteristics have been discussed. The fresh and hardened properties of these mixes and hydrogen loading and its effect on neutron radiation shielding have been discussed. © 2019 Elsevier Ltd. All rights reserved.Item Alkali-activated concrete systems: A state of art(Elsevier, 2020) Manjunath, R.; Narasimhan, M.C.Concrete is one of the most extensively used construction materials in the world. Production of ordinary Portland cement, the major constituent in the production of concrete, is leading to large-scale exploitation of the natural reserves of limestones, clays, and coal. It is estimated that there is a release of 0.8-1.0 tons of carbon dioxide to the atmosphere for the production of every ton of cement. In view of this, alternative construction materials are being developed, using industrial by-products such as fly-ash, ground granulated blast furnace slag, and metakaolin, which are generally rich in alumina and silica. The development of alkali-activated concrete systems has attracted the attention of concrete researchers in recent years. This chapter discusses the performance of alkali-activated concrete systems with different binders and alternate aggregates, in terms of their mechanical properties, durability, performance on exposure to elevated temperatures, performance on inclusion of fibers, and finally their suitability for use in structural members. © 2020 Elsevier Inc. All rights reserved.Item Numerical Modeling of Geopolymer Concrete Short Columns Reinforced with GFRP Bars Under Different Loading Conditions(Springer Science+Business Media, 2025) Guruprasad, T.N.; Prashanth, M.H.; Narasimhan, M.C.; Manjunath, L.Infrastructure developments are on the increase all around the world. Building these modern infrastructural facilities requires large amounts of steel and concrete. India is one of the world's largest producers of steel and cement. However, to produce one ton each of steel and cement, 1.85 tons and one ton, respectively, of CO2 is released into the environment, contributing immensely to global warming. Again, embedded steel bar corrosion is the main threat to the durability of the reinforced concrete elements. So, Glass fiber-reinforced polymer bars and geopolymer concrete can be employed in RC elements, like columns, for enhanced sustainability. A sustainable and green alternative to OPC concrete is geopolymer concrete (GPC), which uses waste residues such as GGBS, flyash, and aggregates to prevent extraction of raw materials and reduce demand for disposal of waste. The current investigation aims to find the effectiveness of using short geopolymer concrete columns reinforced with GFRP bars. The present study performs a 3D finite element analysis over geopolymer concrete-based short columns with GFRP bars. A representative with a total 1200 mm height and 160 mm × 260 mm cross-section is considered for the GFRP bars reinforced columns under different conditions of loading. Results of FEA analysis carried out using the commercial ANSYS software show that reinforcing the RC short columns with GFRP bars is effective in that they exhibit 10% more buckling strength and 40% more in compression under concentric loading as compared to eccentric loading and also the deformation in the eccentrically loaded column is 50% more when compared to concentrically loaded GFRP RC short column. © 2025 The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.Item Performance of Geopolymer concrete mixes at elevated temperatures(2012) Kishanrao, M.P.; Narasimhan, M.C.Reducing the greenhouse gas emissions is the need of the hour. Five to eight percent of the world's man-made greenhouse gas emissions are from the Cement industry itself. It is an established fact that the green house gas emissions are reduced by 80% in Geopolymer concrete vis-a-vis the conventional Portland cement manufacturing, as it does not involve carbonate burns etc. Thus Geopolymer based Concrete is highly environment friendly and the same time it can be made a high-performance concrete. In the present study, fly ash, blast furnace slag and catalytic liquids have been used to prepare Geopolymer concrete mixes. This study is continued to investigate the behaviour of such Geopolymer concrete under high temperatures ranging from 100°C to 500°C. Cubes of size 100mm × 100mm × 100 mm are tested for their residual compressive strengths after subjecting them to these high temperatures. © 2012 IEEE.Item High Strength Flowable Alkali Activated Slag Concrete Mixes produced using industrial wastes(Institute of Physics Publishing helen.craven@iop.org, 2019) Manjunath, R.; Narasimhan, M.C.A new class of High-Strength Flow ableAlkali activated Slag Concrete(HSFASC)mixes is developed using steel slag sand and EAF (Electric Arc Furnace) slag aggregates, respectively, as the fine and coarse aggregates. These mixes use the ground granulated blast furnace slag as the source material. Thus it is to be recognized that all the three materials used - GGBFS, slag sand and EAF slag aggregates are by-products of the Iron and Steel Industry, and are available in very large quantities demanding safe disposal. Different amounts of Sodium silicate solutions, with specified amounts of Sodium Hydroxide flakes dissolved in them, are used as alkaline solutions. Test specimens were cast using a total of nine HSFASC mixes, (based on Taguchi's Method), each of which satisfied the relevant EFNARC guidelines with respect to their rheological properties. The test results indicate higher compressive strengths values for all the mixes tested herein. Microstructure studies are conducted on samples from the fractured surfaces of test specimens of different mixes, using advanced SEM, EDX and XRD analyses and the results are discussed. © 2019 IOP Publishing Ltd. All rights reserved.Item Effect of addition of OPC on Performance characteristics of Self-compacting Alkali activated slag concrete mixes(Institute of Physics Publishing helen.craven@iop.org, 2019) Manjunath, R.; Narasimhan, M.C.An attempt has been made in the present research to develop construction friendly, self-compacting, alkali-activated slag concrete mixes with ground granulated blast furnace slag (GGBFS) as the major source of binder material. In an effort to make the concrete mixes more eco-friendly and sustainable, by-products from Iron and Steel Industry such as steel slag sand and Electric Arc Furnace (EAF) slag aggregates, were used as the fine and coarse aggregates respectively. While the total binder content has been varied in the range of 700 - 800 kg/m3 (in increments of 50 kg/m3), all the trial mixes had a constant w/b ratio of 0.40. Different amounts of sodium silicate solutions, with specified amounts of sodium hydroxide flakes dissolved in them, are used as alkaline solutions, with the combined Na2O percentage in them varying between 6% - 8%. Test specimens were cast with mixes which showed enhanced flow-properties as per relevant EFNARC guidelines and were tested for their mechanical strength and durability characteristics. Effect of admixing of ordinary Portland cement (OPC) in smaller percentages (2.5% - 10 %, in increments of 2.5%), on the performance characteristics of this novel class of AAC mixes is evaluated. Increased cement contents are found to lead to better flow ability properties and higher strengths values with lower sorptivity values in all the Cement-Admixed, Self-compacting, Alkali-Activated Slag Concrete mixes (CASAASC mixes) tested herein. Studies with a scanning electron microscope have shown more densified morphologies developed, accounting for better performances of these mixes. © 2019 IOP Publishing Ltd. All rights reserved.Item Experimental studies on shear strength characteristics of alkali activated slag concrete mixes(Elsevier Ltd, 2020) Manjunath, R.; Narasimhan, M.C.; Shashanka, M.; Vijayanand, S.D.; Vinayaka, J.In the present study an attempt has made to study the shear strength characteristics of alkali activated slag concrete mixes developed using steel slag sand and Electric Arc Furnace (EAF) slag aggregates, respectively, as the fine and coarse aggregates. These mixes use the ground granulated blast furnace slag (GGBFS) as the primary source material. Thus it is to be recognized that all the three materials used-GGBFS, slag sand and EAF slag aggregates are by-products of the Iron and Steel Industry, and are available in very large quantities demanding safe disposal. Different amounts of Sodium silicate solutions, with specified amounts of Sodium hydroxide flakes dissolved in them, are used as alkaline solutions. The test results indicate higher compressive strengths values for all the mixes in the range of 50-70 MPa with their shear strength values ranging between 7.5 and 12.0 MPa. Further the relationship between shear strength and compressive strength of the AASC mixes was also developed. © 2019 Elsevier Ltd. All rights reserved.Item Effect of binder chemistry on sulphate resistance of fly-ash blended cement concrete mixes(Institute of Physics Publishing helen.craven@iop.org, 2020) Nazeer, M.; Narasimhan, M.C.; Rajeeva, S.V.The chemical durability of concretes exposed to sulphate environment largely depends on the quality and quantity of products of cement hydration. Certain hydration products are readily reactive with the sulphate ions and form expansive products such as gypsum and ettringite. On the other hand, some sulphate compounds participate in reducing the cementing property of hydration products. These reactions cause expansion and deterioration of strength of concrete. Sulphate resistance of concrete can be improved by the incorporation of Supplementary Cementitious Materials (SCMs). Reduced water-binder ratio and proper curing can make concrete more durable in sulphate environment. This paper reports the details and results of an investigation of effect of chemical composition of binder materials on the sulphate resisting property of concrete exposed to a rich MgSO4 solution. The effect of initial curing is also investigated so that it may be possible to suggest the mix compositions for typical field applications of concrete. The variables investigated in this report are the oxide composition of binder components and the initial curing conditions. A set of concrete mixes, all with a constant binder content and water-binder ratio are used in the investigation. © 2020 Published under licence by IOP Publishing Ltd.Item Performance evaluation of steel fiber-reinforced deep beams using self-compacting concrete(Springer Science and Business Media Deutschland GmbH, 2021) Manjunath, R.; Narasimhan, M.C.; JanagamReinforced self-compacting deep beams were developed, and their performance with varying percentages of steel fibers has been investigated in the present research. Fine aggregate being river sand along with 12.5 mm downsize jelly as coarse aggregate, and all the concrete mixes were proportioned for attaining a strength of M-30 grade concrete. Based on standard code IS: 456-2000, all the reinforced SCC deep beams were designed. As per the EFNARC guidelines, all the SCC mixes were subjected to different flowability tests for ascertaining the concrete as SCC mixes. Test results concluded that the ultimate flexural strength of the reinforced concrete deep beams increased with the increase in the percentage of steel fibers due to the better stitching actions of the steel fibers with the cementitious matrix. © Springer Nature Singapore Pte Ltd 2021.Item Performance evaluation of deep beams using self-compacting concrete subjected to corrosion(Springer Science and Business Media Deutschland GmbH, 2021) Manjunath, R.; Narasimhan, M.C.; Bibesh Nambiar, C.Effect of corrosion on RCC–SCC deep beams subjected to three different percentages of corrosion have been investigated in the present study. These SCC mixes were designed for obtaining a cube strength of M-30 grade using river sand as finer portions of the aggregate and 12.5 mm downsize jelly as coarse aggregate. Design of SCC reinforced concrete deep beams was carried out as per IS-456:2000 and the accelerated corrosion technique has been employed for carrying out the corrosion. All the trial SCC mixes were subjected to different flow ability tests in order to evaluate their SCC property as per the EFNARC guidelines. From the obtained test results, it can be observed that for the lower percentage of corrosion decrease in ultimate flexural strength was observed due to decrease in arch action. Further with increase in percentage of corrosion showed an increased ultimate flexural strength due to increase in arch action. © Springer Nature Singapore Pte Ltd 2021.