Faculty Publications
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Item 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 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.