Faculty Publications
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Item Effect of different curing regimes and durations on early strength development of reactive powder concrete(Elsevier Ltd, 2017) Hiremath, P.N.; Yaragal, S.C.The early strength development of Reactive Powder Concrete (RPC) has been investigated under different curing regimes and compared with standard water curing condition. Four different curing regimes have been considered: ambient air curing, hot air curing, hot water bath curing and accelerated curing. The effect of hot air curing on strength development of RPC at different temperatures and durations are studied in detail. The present study is focused on the effect of combined curing regimes on the early strength development of RPC. Test results indicate that, among the four different curing regimes, hot water bath curing gives higher strength. The combined curing regime has considerably enhanced the compressive strength of RPC by about 63% as is evident by the rise in compressive strength from 110 MPa (standard curing) to 180 MPa (combined curing). Microstructure studies were also conducted to understand the arrangements of hydrated particles and development of other secondary hydrated products under different curing conditions using scanning electron microscope and X-ray diffraction spectroscopy respectively. © 2017 Elsevier LtdItem Ferrochrome ash – Its usage potential in alkali activated slag mortars(Elsevier Ltd, 2020) Kumar, K.B.; Yaragal, S.C.; Das, B.B.This study is an attempt to develop a sustainable construction material, i.e., alkali activated slag (AAS) in combination with ferrochrome ash (FCA) as a replacement to ordinary Portland cement (OPC). The effect of the various levels of FCA (0, 25, and 50%) replacing ground granulated blast furnace slag (GGBS) in AAS mortars with 4% of Na2O dosage is studied. Further, five levels of the modulus of silica (Ms = 0.75, 1.00, 1.25, 1.5, and 1.75) are chosen to achieve targeted compressive strength at 28 days under ambient temperature curing conditions. The compressive strength decreases with the increase in level of the FCA replacement. The targeted design compressive strength is achieved with 25% FCA replacement to GGBS in the AAS mortar system with Ms = 1.25. In addition, microstructure and mineralogical studies are undertaken to ascertain the formation of different hydration products with the aid of the scanning electron microscope (SEM) and the X-ray diffractometer (XRD). Gismondine and calcium aluminate silicate hydrate (C-A-S-H) are the major hydration products in the AAS mortar mixes. Sodium aluminate silicate hydrate phases (N-A-S-H) are also observed prominently as the FCA replacement level increases in the AAS mortar mixes. The Fourier-transform infrared spectroscopy (FTIR) confirms the presence of the Si–O-(Si or Al) functional group. The addition of FCA in the AAS system is of vital significance in the reduction of the embodied carbon dioxide (ECO2eq), embodied energy (EEeq) and cost. © 2020 Elsevier LtdItem Performance and microstructural investigations of processed lateritic fine aggregates in blended cement mortars exposed to elevated temperatures(Emerald Publishing, 2023) Basavana Gowda, S.N.; Yaragal, S.C.; C, C.; Goudar, S.K.Purpose: In recent years, fire accidents in engineering structures have often been reported worldwide, leading to a severe risk to life and property safety. The present study is carried out to evaluate the performance of Ground Granulated Blast Furnace Slag (GGBS) and fly ash–blended laterized mortars at elevated temperatures. Design/methodology/approach: This test program includes the replacement of natural river sand with lateritic fine aggregates (lateritic FA) in terms of 0, 50 and 100%. Also, the ordinary Portland cement (OPC) was replaced with fly ash and GGBS in terms of 10, 20, 30% and 20, 40 and 60%, respectively, for producing blended mortars. Findings: This paper presents results related to the determination of residual compressive strengths of lateritic fine aggregates-based cement mortars with part replacement of cement by fly ash and GGBS exposed to elevated temperatures. The effect of elevated temperatures on the physical and mechanical properties was evaluated with the help of microstructure studies and the quantification of hydration products. Originality/value: A sustainable cement mortar was produced by replacing natural river sand with lateritic fine aggregates. The thermal strength deterioration features were assessed by exposing the control specimens and lateritic fine aggregates-based cement mortars to elevated temperatures. Changes in the mechanical properties were evaluated through a quantitative microstructure study using scanning electron microscopy (SEM) images. The phase change of hydration products after exposure to elevated temperatures was qualitatively analyzed by greyscale thresholding of SEM images using Image J software. © 2023, Emerald Publishing Limited.Item 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 Ltd