Faculty Publications
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Item 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.Item High temperature performance of self-compacting high-volume fly ash concrete mixes(2011) Amrutha; Nayak, G.; Narasimhan, M.C.; Rajeeva, S.V.Quite often, concrete in structures is likely to get exposed to high temperatures, including an incident of fire. The strength-retention properties of concrete after such an exposure are of great importance in terms of the serviceability of buildings. This paper presents an experimental study on the strength retention and impermeability aspects of a set of self compacting, high-volume fly ash concrete mixes under elevated temperatures. Five selfcompacting concrete mixes with a higher 60% level of cement replacement with fly-ash, are designed and the effects of elevated temperatures, in the range of 200-800 C, on the physical, mechanical and durability properties of these mixes are assessed. The assessment is in terms of the weight losses and the reduction in the compressive strengths of concrete cubes and split tensile strengths of concrete cylinders. The durability characteristics are assessed in terms of RCPT test results on these mixes. Performances of these self compacting concrete mixes (SCC) at elevated temperatures are also compared with two normally-vibrated concrete mixes (NCs) of an equivalent M30 strength grade. Test results indicate that weight of the specimens significantly get reduced with an increase in the level of elevated temperature, with sharp variations beyond 600 C. The experimental results also show that large improvements against chloride-ion penetration and better strength-retention at higher temperatures can be realized with self-compacting high-volume fly-ash concrete mixes additionally admixed with GGBFS and silica fume.Item Predicting compressive strength of SCC mixtures using artif icial neural network(2012) Rame Gowda, M.; Narasimhan, M.C.; Karisiddappa; Kumuda, T.Over the last few years, the use of artificial neural networks (ANNs) has increased in many areas of engineering. In particular it is increasingly being used in concrete engineering problems. Since accurate estimation of compressive strength of self-compacting concrete (SCC) is an important issue in concrete engineering this paper describes the development of ANN models based on laboratory SCC mixes. The multilayer feed-forward type network models were trained using the back-propagation method with a momentum factor. The data obtained from the mix design exercises were employed to develop and test the performance of the models. A new concept of using more than one error statistic resulted in efficiently training the models and improving its generalization capability.Item Neutron radiation shielding properties of polymer incorporated self compacting concrete mixes(Elsevier Ltd, 2017) Malkapur, S.M.; Divakar, L.; Narasimhan, M.C.; Karkera, N.B.; Goverdhan, P.; Sathian, V.; Prasad, N.K.In this work, the neutron radiation shielding characteristics of a class of novel polymer-incorporated self-compacting concrete (PISCC) mixes are evaluated. Pulverized high density polyethylene (HDPE) material was used, at three different reference volumes, as a partial replacement to river sand in conventional concrete mixes. By such partial replacement of sand with polymer, additional hydrogen contents are incorporated in these concrete mixes and their effect on the neutron radiation shielding properties are studied. It has been observed from the initial set of experiments that there is a definite trend of reductions in the neutron flux and dose transmission factor values in these PISCC mixes vis-à-vis ordinary concrete mix. Also, the fact that quite similar enhanced shielding results are recorded even when reprocessed HDPE material is used in lieu of the virgin HDPE attracts further attention. © 2017 Elsevier LtdItem Fresh and hardened properties of polymer incorporated self compacting concrete mixes for neutron radiation shielding(Elsevier Ltd, 2017) Malkapur, S.M.; Divakar, L.; Narasimhan, M.C.; Karkera, N.B.; Goverdhan, P.; Sathian, V.; Prasad, N.K.Several works in the past have reported that the hydrogen content in the hydrated concrete plays an important role in shielding the neutron radiation; higher the hydrogen content, better is the neutron radiation shielding. In this study, pulverised high density polyethylene (HDPE) material is used as an additional source of hydrogen within concrete to develop a novel class of Polymer-Incorporated Self-Compacting Concrete (PISCC) mixes for enhanced neutron radiation shielding. The HDPE material was incorporated as a partial replacement to river sand. It is found that the PISCC mixes have satisfactory fresh and hardened properties and enhanced neutron radiation shielding properties. © 2017 Elsevier LtdItem 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 LtdItem 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 LtdItem 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 LtdItem 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.Item 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.