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 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.