Faculty Publications

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    Studies on fresh and hardened properties of sugarcane bagasse ash blended self-compacting concrete mixes
    (Springer, 2019) Manjunath, R.; Rahul, M.
    Several industrial by-products are used as alternative supplementary cementitious materials in concrete. Sugar cane bagasse ash (SCBA) is one industrial by-product which is mainly composed of amorphous silica and hence can be used as a pozzolanic admixture in concrete. In the present study, an attempt has been made to produce self-compacting concrete mixes, using sugar cane bagasse ash (SCBA) as a cementitious admixture. The study investigates the fresh properties of such as slump flow, V-funnel and L-box of these self-compacting concrete mixes along with their hardened properties such as compressive strength, splitting tensile strength and water absorption values. SCBA-based SCC mixes were produced with varying cement content in the range of 450–500 kg/m3 (increment of 25 kg/m3), along with different levels of replacements of cement with SCBA (in the range of 10–40%). A constant w/b ratio of 0.45 was adopted in all the varied mixes. Results indicate satisfactory rheological properties for the mixes (slump flow greater than 650 mm), with their water absorption values in the range of (3–4.5%). © Springer Nature Singapore Pte Ltd. 2019.
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    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.
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    Experimental Studies on Self-Compacting Alkali Activated Slag Concrete Mixes Incorporating Reclaimed Asphalt Pavement as Fine Aggregate
    (Trans Tech Publications Ltd, 2023) Joy, A.; Manjunath, R.; Neha, S.N.; Prashanth, M.H.
    Here performance evaluation of Self Compacting Alkali Activated Slag Concrete incorporating Reclaimed Asphalt Pavement as fine aggregate was carried out. Investigation on mechanical properties by replacing the fine aggregate by Reclaimed Asphalt Pavement in different proportions were also evaluated. Development of Self Compacting Alkali Activated Concrete mixes (SCAAC) was made with GGBFS and Lime are used binders, with binder content varying between 550 to 650 kg/m3 of fresh concrete and lime content varying from 10% to 20% of binder content. The net W/B ratio of the mixes was kept around 0.57. The fine aggregate was replaced by Reclaimed Asphalt Pavement with percentage replacement from 50 to 100% of Crushed Stone Sand. The alkaline solutions had Na2O dosage percentages in the range 5-6% with a constant activator modulus maintained at 1. By using Minitab Statistical Software nine mixes were produced with 4 factors and 3 levels. In this study the TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) optimization technique was carried out to know the effectiveness. Results showed the slump flow greater than 650 mm, with their L–Box, U-box and V-Funnel values ranging between 0.85,20mm and10s respectively, results showed enhanced mechanical properties as compared to control OPCC mix. © 2023 Trans Tech Publications Ltd, All Rights Reserved.
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    Performance Evaluation of Fly-ash based Self-compacting geopolymer concrete mixes
    (Institute of Physics Publishing helen.craven@iop.org, 2019) Manjunath, R.; Ranganath, R.V.
    In this paper, an attempt has been made to develop Fly ash based self- compacting geopolymer concrete mixes with varying volume of pastes using conventionally available river sand as fine aggregate and crushed granite chips as coarse aggregate. These mixes were developed usingFly ash as the only major source material in the production of SCC mixes. Different amounts of Sodium silicate solutions, with specified amounts of Sodium Hydroxide flakes dissolved in them, are used as alkaline solutions. The total of four mixes were developed with varying volume of pastes in the range of 0.40 - 0.52 (within an interval of 0.04). These mixes were evaluated for their flow ability characteristics as per the relevant EFNARC guidelines. Further the mixes were evaluated for their mechanical properties in terms of compressive strength, splitting tensile strength and water absorption characteristics. Durability tests by means of subjecting to acidic and sulphate environments, along with their resistances to sustained elevated temperatures for a sustained period of 2 hours upto 800° C were carried out for all these mixes. The test results indicate better flow ability characteristics, along with their mechanical and durability properties. © 2019 IOP Publishing Ltd. All rights reserved.
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    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.
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    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.
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    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.
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    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.; Janagam
    Reinforced 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.
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    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.
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    Stone Columns with Vertical Circumferential Nails: Laboratory Model Study
    (2010) Shivashankar, R.; Dheerendra Babu, M.R.D.; Nayak, S.; Manjunath, R.
    This paper presents results from a series of laboratory plate load tests carried out in unit cell tanks to investigate the improvement in stiffness, load carrying capacity and resistance to bulging of stone columns installed in soft soils. A new method of reinforcing the stone columns with vertical nails installed along the circumference of the stone column is suggested for improving the performance of these columns. Tests were carried out with two types of loading (1) the entire area in the unit cell tank loaded, to estimate the stiffness of improved ground and (2) only the stone column loaded, to estimate the limiting axial capacity. It is found that stone columns reinforced with vertical nails along the circumference have much higher load carrying capacity and undergo lesser compression and lesser lateral bulging as compared to conventional stone columns. The benefit of vertical circumferential nails increases with increase in the diameter, number and depth of embedment of the nails. The improvement in the performance of stone column was found to be more significant, even with lower area ratio. It is found that reinforcing stone column with vertical circumferential nails at the top portion to a depth equal to three times the diameter of stone columns, will be adequate to prevent the column from excessive bulging and to improve its load carrying capacity substantially. © 2010 Springer Science+Business Media B.V.