Faculty Publications
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Item Processing of laboratory concrete demolition waste using ball mill(Elsevier Ltd, 2023) Rakesh Kumar Reddy, R.; Yaragal, S.C.; Sanjay, V.K.The demand for natural aggregates in the twenty-first century is at an all-time high due to rapid urbanisation and infrastructure development. Finding alternative aggregate materials is a challenge for achieving construction sustainability. Both the depletion of natural resources and the improper disposal of construction and demolition (C&D) waste can be ameliorated by the widespread use of recycled aggregates in construction. Due to the attached mortar, aggregates from C&D waste must be processed before using them in concrete. Various combinations of ball mill processing parameters were used to produce relatively higher-quality aggregates. Water absorption was used as the primary criterion for determining the quality of processed aggregates. The water absorption capacity of recycled coarse aggregate was found to be decreased from 5.8% to 1.5% as a result of effectively removing the attached mortar by employing ball mill processing. Specific gravity, impact, and crushing values are also improved after processing, as discussed and illustrated in this paper. © 2023Item A novel approach for optimizing the processing of recycled coarse aggregates(Elsevier Ltd, 2023) Rakesh Kumar Reddy, R.; Yaragal, S.C.This paper proposes an alternative method for processing the demolition waste into high-quality recycled coarse aggregate using the ball mill. Taguchi's design of experiments based on orthogonal array was used to minimize the number of trials for saving material and time. Experiments were carried out based on L25 orthogonal array with three processing parameters: charge, revolution duration, and aggregate weight with five levels. The revolution speed of the ball mill was set to 60 revolutions per minute. The Taguchi method was then combined with grey relational analysis to achieve the best combination of processing parameters for producing high-quality aggregate. Experimental studies on water absorption, specific gravity, impact value, and abrasion value were used to assess the quality of recycled coarse aggregates. The best combination for each performance characteristic was achieved by using the mean of Signal to Noise ratio graphs. The optimal combination of processing parameter levels to generate superior quality recycled aggregates and the most significant processing parameter were identified based on the response table of means of grey relation grade. © 2023 Elsevier LtdItem One-part eco-friendly alkali-activated concrete – An innovative sustainable alternative(Elsevier Ltd, 2023) Rakesh Kumar Reddy, R.; Yaragal, S.C.; Srinivasa, A.S.The primary objective of this study is to develop an eco-friendly one-part alkali-activated concrete (OPAAC) by incorporating a combination of fly ash (FA), ground granulated blast furnace slag (GGBS), and micro silica (MS). In this investigation, the proportion of MS is maintained at 20% of FA, while the maximum replacement of FA with GGBS is set to 60%, varying in 20% intervals (i.e., 0%, 20%, 40%, and 60%). Further, the natural aggregates (NA) are substituted with recycled coarse aggregates (RCAs), ferrochrome slag aggregates (FCSAs), or a combination of both. The influence of GGBS and alternative aggregates (RCAs, FCSAs) on the mechanical properties of OPAAC is thoroughly examined. To provide a comprehensive assessment, the properties of OPAAC are compared against Ordinary Portland Cement (OPC) concrete (CC) of equivalent grades. Additionally, microstructural and mineralogical investigations are conducted to determine the formation of distinct hydration products, utilizing scanning electron microscopy (SEM) and X-ray diffractometry (XRD) techniques. In OPAAC containing FA, the primary hydration products identified are alkaline alumino silicate hydrates (CASH and NASH). As the GGBS content increases, calcium silicate hydrate (CSH) becomes the predominant hydration product. Furthermore, in order to assess the sustainability of OPAAC, an analysis of embodied CO2 emissions is performed, and the results are compared with CC and alkali-activated concrete. Notably, OPAAC comprising 40% FA replaced with GGBS, 50% RCAs, and 50% FCSAs demonstrates the most favourable mechanical properties and exhibits lower CO2 emissions. © 2023 Elsevier LtdItem Multi-objective optimization of one-part geopolymer mortars adopting response surface method(Elsevier Ltd, 2023) Srinivasa, A.S.; Yaragal, S.C.; Swaminathan, K.; Rakesh Kumar Reddy, R.One-part geopolymers have immense potential in large-scale structures owing to their improved safety and convenience of handling over the conventional geopolymer mixing procedure. Thus, this study aims at optimizing the mixes by assessing the influence of binder content, activator dosage and water to geopolymer solids (W/GS) ratio on the flowability, strength, and shrinkage properties of one-part geopolymer mortars (OPGM). The test results were utilized to develop models that could predict the desired properties of mixes and optimize the mix proportions of OPGMs using the response surface method. The fly ash and slag-based OPGMs were developed. The GGBS substitution was chosen as 25, 50, and 75% by volume of fly ash. The activator dosage was taken as 8, 12, and 16% by mass of total binder content at varied W/GS ratios of 0.35, 0.40, and 0.45. The responses considered were flowability, compressive and flexural strengths at 7 and 28 days, and drying shrinkage of up to 180 days. Total of 504 specimen were cast to record the observations for this optimization study. The GGBS content, W/GS ratio, and combined effect of these factors were found to be the most influential factors affecting the responses. The optimal mix proportion obtained consists of 49.8% GGBS, 13.6% activator dosage, and 0.37 W/GS ratio. This mix achieved 170.4 mm flow, 57.8 MPa and 5.9 MPa compressive and flexural strengths, respectively and also 1626 microstrain of 180 days drying shrinkage. The microstructural characterization adopting techniques like SEM, XRD, TGA and FTIR was carried out to study microstructural changes, mineral phases, thermal mass loss and molecular bonding of OPGM mixes. This study revealed that mix with 50% GGBS, 12% activator dosage and 0.40 W/GS ratio can better be characterized compared to other mixes. © 2023 Elsevier Ltd