Faculty Publications
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Item Studies on iron tailings towards usage for paving blocks manufacture(2010) Mangalpady, M.; Sampath Kumar, N.N.Disposal of mill tailings is one of the major problems in mining industry. Investigations are being done all over the world to utilize tailings for useful purposes. The scope of this work is to study the utilization of iron ore tailings in manufacture of concrete paving blocks. Five reference mixes were prepared using cement, jelly dust and baby jelly. Ten paving blocks were prepared from each type of mix, out of which five specimens were cured for 7 days and five were cured for 28 days. By using sand and tailings as fine aggregates, two modified mixes were prepared by replacing jelly dust partly in reference mixes. Similar to reference mix, five mix ratios were made and ten paving blocks were prepared from each type of mixtures. From each set of paving blocks, five specimens were cured for 7 days and the other five specimens were cured for 28 days. Laboratory tests were conducted to assess water absorption and compressive strength of specimens, and graphs were plotted for their comparison among each type of respective mix ratios. In all the comparisons, compressive strength of tailing based mix was higher than the respective reference mix. Similar trend is shown by the graphs plotted for water absorption. © 2010 CAFET-INNOVA TECHNICAL SOCIETY. 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 Study on the strength parameters of high volume fly ash concrete and geopolymer concrete(2011) Shetty, A.; Anand, V.R.; Hegde, P.Concrete has been the most preferred construction material. It is being increasingly used day by day all over the world due to its versatility, mould ability and high compressive strength. But the large-scale production of cement is causing environmental problems on one hand and the unrestricted depletion of natural resources on the other. So the issue of sustainable development in concrete construction is addressed in this paper through development of concrete mixes by replacing certain percentage of cement with fly ash. Trials on concrete mixes with replacement of 40%, 50%, 60% and 70% of cement with fly ash are carried out and the results depict that at the replacement level of 40% cement by fly ash, the required strength is achieved. It is also observed that the rate of early strength gain is retarded as the percentage replacement of cement increases. But in case of Geopolymer concrete (100% replacement of cement by fly ash) under a curing temperature around 600C and above, the strength gain rate is very high in initial stages. It is observed that design strength is achieved within 28 hours of oven curing. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.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 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 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 Multi-criteria optimization of fly ash and iron ore tailing based concretes subjected to elevated temperatures(Associated Cement Companies Ltd., 2019) Yaragal, S.C.; Babu Narayan, K.S.; Kumar, B.; Francis, J.G.Due to the rapid increase in concrete utilization all over the world, there is increased consumption of Ordinary Portland Cement (OPC), natural fine aggregate (NFA), and natural coarse aggregates. Increased use of OPC, is posing a serious threat due to excess CO2 emissions, and its production is highly energy intensive. On the other hand, extraction and processing stone-based fine and coarse aggregates too, is energy intensive, and the virgin resources are fast depleting. Therefore, for sustainable development, efforts are on all over the world to look for alternative materials in place of conventional ones. In this study, it is attempted to partly replace OPC with fly ash (FA) and partly replace NFA by iron ore tailings (IOT) in concretes. The performance of such concretes at ambient and elevated temperatures is also presented. Full factorial design of experiments was adopted with two control factors under three levels of replacement, i.e., FA (0, 15, and 30% by weight of OPC) and IOT (0, 50, and 100% by volume of NFA). Total nine concrete mixes were prepared and tested for their compressive strengths at room temperature, and residual compressive strengths when subjected to various levels of elevated temperatures (200, 400, 600, and 800°C), and cost of these concretes has also been analyzed. Further, three traditional multi–criteria optimization methods, i.e., grey relational analysis (GRA), technique for order of preference by similarity to ideal solution (TOPSIS), and desirability function approach (DFA) were used to optimize concrete mixes. Results showed that TOPSIS based optimization method is more significant when compared to other two methods. Further, FA-based concrete mixes showed improved performance under multi-criteria optimization. © 2019, Associated Cement Companies Ltd. All rights reserved.Item 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