Faculty Publications
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Item 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 Research on Setting Time, Compressive Strength and Microstructure of Fly Ash-Based Geopolymer Mixture Containing Slag(Springer Science and Business Media Deutschland GmbH, 2023) Prasanna, K.M.; Sharath, B.P.; Choukade, H.; Shivaprasad, K.N.; Das, B.B.; Mahesh, G.This study focusses on upgrading the fresh and hardened properties of fly ash-based geopolymer mix samples such as initial and final setting time, flow table test and compressive strength with the substitution of ground granulated blast furnace slag at varied percentage levels and with different alkali binder ratios. Substitution of slag in geopolymer mix samples is important so as to achieve fast setting characteristics in the product. For studying these effects on the microstructure of the product, scanning electron microscopy (SEM) with energy dispersive spectroscopy and Fourier transform infrared spectroscopy were conducted. The experimental outcomes stated that an increase in slag substitution has decreased the setting time and increased the compressive strength of geopolymer mix samples. SEM images have revealed the occurrence of a dense matrix with the slag substitution. FTIR results stated that shifting in wavenumbers of characteristic bands to lower numbers for varied slag substitution levels indicates a greater extent of geopolymerization. © 2022, The Author(s), under exclusive licence to Shiraz University.Item Influence of Geopolymerization Factors on Sustainable Production of Pelletized Fly Ash-Based Aggregates Admixed with Bentonite, Lime, and GGBS(American Society of Civil Engineers (ASCE), 2023) Sharath, B.P.; Snehal, K.; Das, B.B.; Barbhuiya, S.This experimental research investigates the influence of geopolymerization factors such as Na2O dosages, water and mineral admixture [bentonite (BT), burnt lime (BL), and ground granulated blast furnace slag (GGBS)] on physiomechanical properties of the pelletized fly ash (FA)-based aggregates. Taguchi's L9 orthogonal array was adopted to design the mixing ratios for three kinds of fly ash-based aggregates (in the combinations of FA-BT, FA-BL, and FA-GGBS). The degree of geopolymerization of the produced aggregates was characterized using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and a scanning electron microscope (SEM). Most influential response indices in the production of pelletized aggregates were identified using gray relational analysis. The physiomechanical characteristics of the fly-ash aggregates were significantly improved by admixing BL than that of GGBS and BT. However, pelletization efficiency was seen to be superior for GGBS-substituted fly-ash aggregates. The quantified amount of hydration products, i.e., sodium alumino-silicate hydrate (N-A-S-H)/calcium alumino-silicate hydrate (C-A-S-H) for fly ash-based aggregates intensified on increasing Na2O and mineral admixture dosages. The results strongly suggest the existence of a linear relationship between the quantified amount of N-A-S-H/C-A-S-H and individual pellet strength of produced aggregate. The FTIR spectrum showed strong and broadened bands of Si-O terminal for all types of aggregates, representing the conversion of unreacted minerals to chains of aluminosilicate gel (geopolymerized hydration product). Further, it can also be inferred from gray relational analysis that among all other factors, Na2O content significantly impacted the engineering properties of produced fly ash-based aggregates. © 2023 American Society of Civil Engineers.Item IMPLICATION OF HIGH-VOLUME MINERAL ADMIXTURE ON MECHANICAL PROPERTIES AND MICROSTRUCTURE AT STEEL-CONCRETE INTERFACE(Associated Cement Companies Ltd., 2023) Goudar, S.K.; Sumukh, E.P.; Das, B.B.The existence of a non-homogeneous unique zone in concrete along the periphery of steel surface is being referred as steel-concrete interface (SCI). The interface between steel and concrete exhibits a porous zone, with a thickness measuring several micrometers. This porous zone thickness around SCI plays a crucial role in influencing bond strength, durability, and is a significant parameter used in service life prediction models for reinforced concrete structures. The value of porous zone thickness around SCI is being assumed and adopted without any practical studies in service life prediction models as well as in reinforced concrete mesoscale structure modelling. In the present study, porous zone thickness was experimentally measured through obtaining backscattered electron images around SCI. Gray scale-based thresholding technique was employed to ascertain the porous zone thickness (PZT) around SCI. Furthermore, the influence of incorporating ground granulated blast furnace slag (GGBS) in high-volume on the interfacial transition zone (ITZ) between steel reinforcement bars and the surrounding concrete was investigated. It was observed that porous zone thickness around SCI varies in every other point along the periphery of reinforcement bar. The pozzolanic reaction in high volume GGBS concrete resulted in a substantial decrease of porous zone thickness (PZT) and reduced the accumulation of Portlandite around SCI with the progress in curing age. The factors contributing to the enhanced ultimate bond strength of high volume GGBS concrete compared to control concrete are the decrease in the Porous Zone Thickness (PZT) along with the reduced Ca/Si ratio around the SCI. © 2023, Associated Cement Companies Ltd.. All rights reserved.Item 3D printing aspects of fly ash and GGBS admixed binary and ternary blended cementitious mortar(Taylor and Francis Ltd., 2025) Mishra, S.K.; Upadhyay, B.; Das, B.B.This study investigates the integration of Ground Granulated Blast Furnace Slag (GGBS) and fly ash to sustainably reduce the usage of Ordinary Portland Cement (OPC) in 3D printable mortar to enhance printability and engineering performance. Four mortar mixes were developed, and their printability parameters, such as flowability, extrudability, open time, yield stress, shape retention, and buildability, were assessed. Among mixes, O70G30 (70% OPC, 30% GGBS) showed the best printability, with an 18.3% and 54.3% higher shape retention factor than the control and O70F30 mixes, respectively, which can be attributed to improved particle packing and 5.5% higher yield stress. However, its open time was 22.2% lower than the control. This reduction can be attributed to the finer particle size and higher specific surface area of GGBS, which increased water demand and accelerated the loss of workability. In the hardened state, O70G30 exhibited 24% lower water absorption and 18.5% reduced permeable porosity than the control, indicating a denser microstructure. Printed specimens exhibited anisotropic strength, with the highest values observed on the YZ plane and the lowest on the ZX plane. Depending on the loading direction and mix composition, their compressive strength was 9.4–35.6% lower than that of mould-cast samples, while the flexural strength improved by 16.19% to 40.18%. Microstructural analysis revealed a denser matrix with a lower Ca/Si ratio and enhanced secondary hydration, evidenced by stronger C–S–H peaks in XRD, pronounced Si–O–Si/Al bands in FTIR, and 41.22% higher bound water (WH) with reduced portlandite (CH) in TGA compared to O70F30. These promising results can be attributed to GGBS’s role in enhancing hydration, refining the microstructure, and improving the performance of 3D printable mortar, offering a sustainable and effective pathway for digital construction. Also, the Life Cycle Impact Analysis (LCIA) revealed that the incorporation of supplementary cementitious materials (SCMs) significantly reduces environmental impacts compared to the control mix. © 2025 Informa UK Limited, trading as Taylor & Francis Group.