Browsing by Author "Manjunath, R."

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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.
An experimental investigation on self-compacting alkali activated slag concrete mixes
(Elsevier Ltd, 2018) Manjunath, R.; Narasimhan, M.C.
In present work, an attempt has been made to develop self-compacting, alkali activated slag concrete mixes, using steel slag sand as fine aggregate and EAF (Electric Arc Furnace) slag as coarse aggregate. The study investigates the properties such as compressive strength, splitting tensile strength and water absorption of these mixes. Development of Self-Compacting Alkali Activated Slag Concrete mixes (hereafter referred to as SCAASC mixes) was made with GGBFS (Ground Granulated Blast Furnace Slag) as the binder, with its content varying between 700 kg/m3 and 900 kg/m3 of fresh concrete. The net W/B (water to binder) ratio of the mixes was varied between a narrow 0.47 – 0.48 range. The alkaline solutions had Na2O percentages in the range 7 – 9%, but a constant activator modulus was maintained at 1.0 in all the mixes. In order to optimise the number of trial mixes to be tested, Taguchi's design of experiments methodology was adopted. A total of nine mixes were formulated using Taguchi orthogonal L9 array. Results showed the slump flow values for the mixes greater than 700 mm, with their L–Box ratios and V-Funnel values ranging between 0.90 and 0.95 and 9 – 11 s respectively, satisfying the EFNARC guidelines. Results also showed good compressive strengths (65–80 MPa), split-tensile strengths (2–4 MPa) and low water absorption values in the range of (2%–3%). The microstructural studies such as SEM, EDX and XRD analysis were also carried out, showing denser morphologies clearly indicating effective activation of slag by the alkaline solution. © 2018 Elsevier Ltd
Bond strength characteristics of fly-ash admixed selfcompacting alkali activated concrete mixes
(Associated Cement Companies Ltd. priti.saldanha@acclimited.com, 2020) Manjunath, R.; Narasimhan, M.C.; Suryanarayana, L.R.
Bonding in any type of concrete plays a crucial role in the performance of reinforced concrete structures, which are profoundly determined by many factors such as concrete compressive strength, diameter, type and size of the bar along with length of embedment and confinement of concrete. Herein, an attempt has been made to develop fly-ash admixed self-compacting alkali activated slag concrete mixes cured under laboratory ambient conditions and to evaluate the bond strength characteristics using direct pull out test along with their bond stress-slip behaviour at the age of 28 and 56 days. These self-compacting alkali activated slag concrete mixes were developed using Fly-ash and GGBFS as the major principal binder. Naturally available river sand was used as the fine aggregate; 12.5 mm down size crushed granite chips (Jelly) constituted the coarse aggregate fractions in all these mixes. The alkaline solutions basically consisted of mixtures of sodium hydroxide flakes dissolved in the calculated quantity of water and mixed with the liquid sodium silicate solution. The experiments were planned based on Taguchi’s design of experiments methodology. A total of fifteen mixes were developed and evaluated for their flow ability characteristics as per the requirements of EFNARC guidelines along with compressive strength values at the age of 7, 14, 28 and 56 days. In an initial, calibration phase, bond strength characteristics of a set of nine mixes were utilized for performance evaluation purposes. Strength prediction equations were then derived on the basis of such results, whose predictive capacity was then evaluated and ascertained in the prediction phase with actual results of experiments on a set of three new mixes. Test results indicated higher flow ability characteristics for all the mixes satisfying the requirements as per the EFNARC guidelines. Higher compressive strengths values in the range of 46 – 85 MPa were obtained at the age of 56 days. Further acceptable bond strength values were obtained varying in the range of 8.0 – 14.5 MPa as compared to control OPC based reference concrete mix. © 2020, Associated Cement Companies Ltd.. All rights reserved.
Effect of addition of OPC on Performance characteristics of Self-compacting Alkali activated slag concrete mixes
(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.
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. Â© 2019 IOP Publishing Ltd. All rights reserved.
Effects of fiber addition on performance of high-performance alkali activated slag concrete mixes: An experimental evaluation
(Taylor and Francis Ltd., 2022) Manjunath, R.; Narasimhan, M.C.; Kumar, S.
There is an ever-increasing awareness on issues connected with emission of high amounts of greenhouse gases from various industries, including that from the concrete construction industry. Performances of alternative binder systems including geopolymers and alkali activated slag concretes are being investigated in this context. There is again a continuous drive to enhance their performances, both when green and on getting hardened and so also, simultaneous efforts are being made to take advantage of all the various fast-track, state-of-art construction technologies, leading to efficient, eco-friendly and economical infrastructure projects. The present authors have developed and evaluated a new set of such alkali activated slag concrete mixes having self-compacting property, along with higher mechanical properties (hereafter referred to as HPAASC mixes) using three industrial by-products, all obtained from iron and steel industry. While these HPAASC mixes have higher compressive strengths (in the range of 70–90 MPa), reasonable split and flexural strengths and are self-compacting, they continue to be brittle just as other high strength concrete mixes. In order to improve their cracking behaviour during failure, either under mechanical loads or on exposure to higher temperatures, addition of increasing amounts of steel fibers in HPAASC mixes is contemplated. Hence in the present study, the attempt is to study the effect of incorporation of fibers (within a small range of 0.4 ? 0.8%) in the new class of high-performance, fibre reinforced. Self-compacting alkali-activated slag concrete mixes–(referred to as HFSASC hereafter). The present study evaluates the properties such as flow ability, compressive strength and flexural toughness performances for these mixes. Results in the present study indicate that, while all the HFSASC mixes exhibit satisfactory passing and flowing abilities specified as per EFNARC standards for self-compacting mixes, they exhibit enhanced toughness characteristics too. © 2020 Informa UK Limited, trading as Taylor & Francis Group.
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.
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. Â© 2019 Elsevier Ltd. All rights reserved.
Experimental study on shear reinforced and shear deficient RC beams subjected to preloading and wrapping with CFRP sheets
(Elsevier Ltd, 2023) Prashanth, M.H.; Manjunath, R.; Koppad, A.; B, B.; Kuttagola, I.
An experimental work has been carried out to study the shear reinforced and shear deficient RC beams which are subjected to preloading and wrapping with CFRP sheets. Shear reinforced beams were wrapped with CFRP sheets and subjected to 0% and 50% preloading. Shear deficient beams were wrapped with CFRP sheets and subjected to 0, 50% and 70% of preloading. CFRP wrapped beams of shear reinforced (A2, A3) and shear deficient (B2 B3 B4) show substantial improvement in ductility and an increased ultimate load carrying capacity when compared to respective control beams. Due to preloading, ductility remains same with the marginal decrease in ultimate load carrying capacity when compared to respective 0% preloaded beam specimens. CFRP wrapping is found to be very effective in arresting initiation and development of cracks with and without preloading. © 2023
Flexural behavior of reinforced high performance self-compacting alkali activated slag concrete beams
(Associated Cement Companies Ltd., 2020) Manjunath, R.; Prashanth, M.H.; Narasimhan, M.C.; Bala Bharathi, U.K.
The present manuscript discusses the results of a series of tests conducted to study, in detail, the performance of reinforced, alkali activated slag concrete beams in terms of their flexural behavior. The present authors have developed and evaluated the performance of a new class of high-performance, self-compacting, alkali-activated slag concrete (HPAASC) mixes, using three industrial by-products, all from the iron and steel industry. While these HPAASC mixes have higher compressive strengths (around 70-90 MPa), reasonable splitting and flexural strengths along with moduli of elasticity, here, in this investigation, reinforced concrete beams made of these mixes are evaluated for their flexural performances in order to promote their applicability in large-scale infrastructural applications. Twelve under-reinforced concrete beams, were cast and were tested. Their flexural behaviors were experimentally evaluated in terms of loads at first crack, ultimate loads, strain-distributions, their load-deflection characteristics along with ductility values. Results of the present study indicate that, all the reinforced beams made of HPAASC mixes exhibit comparable flexural performances, as compared to that of beams cast with a reference OPC-based concrete mix, making a strong case for the possible application of these HPAASC mixes as structural elements in large-scale infrastructure projects. © 2020, Associated Cement Companies Ltd.. All rights reserved.
High Strength Flowable Alkali Activated Slag Concrete Mixes produced using industrial wastes
(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.
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. Â© 2019 IOP Publishing Ltd. All rights reserved.
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 RCCâ€“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 12.5Â 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. Â© Springer Nature Singapore Pte Ltd 2021.
Performance Evaluation of Fly-ash based Self-compacting geopolymer concrete mixes
(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.
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 800Â° C were carried out for all these mixes. The test results indicate better flow ability characteristics, along with their mechanical and durability properties. Â© 2019 IOP Publishing Ltd. All rights reserved.
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 12.5Â 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. Â© Springer Nature Singapore Pte Ltd 2021.
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.
Studies on development of high performance, self-compacting alkali activated slag concrete mixes using industrial wastes
(Elsevier Ltd, 2019) Manjunath, R.; Narasimhan, M.C.; Umesh, K.M.; Kumar, S.; Bala Bharathi, U.K.
In the present study, development of a class of High Performance Alkali Activated Slag Concrete mixes (hereafter referred to as HPAASC mixes) is discussed. These mixes are developed using three industrial wastes from Iron and Steel industry. While Ground granulated blast furnace slag (GGBFS) was used as the main binder, in the development of these HPAASC mixes, steel slag sand and Electric Arc Furnace slag (EAF slag) have been employed in the fine aggregate and coarse aggregate fractions of them. Higher flow characteristics, as those of self-compacting concrete mixes, as well as enhanced mechanical strength properties of these mixes are discussed in detail. The alkaline solutions used consist mixtures of sodium hydroxide and sodium silicate solutions, with a constant activator modulus (ratio of SiO2/Na2O) of one maintained in them. Taguchi’ design of experiments methodology was used to reduce the experimental efforts. The formulation of all the mixes developed herein was based on Taguchi's L-9 orthogonal array. Flow and strength properties of a set of nine mixes were used for performance evaluation purposes in an initial, calibration phase. Strength prediction equations were derived based on such results, the predictive capability of which were then assessed and ascertained with actual results of experiments on the next six new mixes, in the prediction phase. Test results indicated a higher flowability values for all the mixes (with slump flows greater than 700 mm), good filling and passing abilities, all satisfying the EFNARC (European Federation of Specialist Construction Chemicals and Concrete Systems) recommendations for SCC mixes. Higher compressive strengths (65–90 MPa), split-tensile strengths (4.8–5.3 MPa), flexural strengths (6.5–7 MPa), and Modulus of Elasticity (30.4–36.2 GPa) were observed along with lower water absorption values (2.1–2.7%) for all the HPAASC mixes tested herein. Microstructure studies were conducted on samples from the fractured surfaces of test specimens from different mixes, using advanced SEM, EDX and XRD analyses and the results are discussed. © 2018 Elsevier Ltd
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.
Studies on high performance alkali activated slag concrete mixes subjected to aggressive environments and sustained elevated temperatures
(Elsevier Ltd, 2019) Manjunath, R.; Narasimhan, M.C.; Umesha, K.M.
In contemporary constructions, there is a continuous drive for enhancing the performances of concrete mixes, both green and as well as on hardened state. Again there are simultaneous efforts to take full advantage of all the various fast-track, state-of-art construction technologies, leading to early completion of efficient, economical and eco-friendly infrastructure projects. The present authors have developed a new class of high performance self-compacting, alkali activated slag concrete mixes (HPAASC) using three industrial by-products, all obtained from iron and steel industry and have evaluated them for their strength properties. While these HPAASC mixes have higher compressive strengths (about 70–90 MPa) and reasonable split-tensile and flexural strengths, they are also self-compacting in nature. In the present paper, the durability performance of this class of mixes on long-term exposure to aggressive environments like acids, sulphates and chlorides is discussed. Strength deteriorations of the standard test specimens subjected to 5% concentrated sulphuric acid solution and so also in 10% magnesium sulphate solution were monitored for a period of one year. The impermeability of the mixes against chloride-ions was evaluated using both Bulk diffusion test (BDT) and the Rapid chloride penetration test (RCPT). Further these mixes were also evaluated for their performance on exposure to sustained elevated temperatures in the range of 200–800 °C. All the specimens were further analysed for their microstructural studies. Results in the present study indicate that, all the HPAASC mixes exhibit better resistances to aggressive environments and sustained elevated temperatures as compared to the OPC-based reference concrete mix. © 2019 Elsevier Ltd