Faculty Publications

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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 Ltd
Combined Effect of Multistage Processing and Treatment Methods on the Physical, Chemical, and Microstructure Properties of Recycled Concrete Aggregates
(ASTM International, 2024) Trivedi, S.S.; Dixit, K.; Das, B.B.; Barbhuiya, S.
This research aims to examine the effects of multistage processing on reducing the old cement fractions and enhancing the quality of concrete recycled aggregate (CRA). The investigation involves the use of demolished concrete debris and subsequent treatments in both single and multistage processes. The recycled aggregates (RAs) were obtained using a multistage jaw crushing process followed by utilizing natural aggregate, untreated RA, RA treated with hydrochloric acid (HCl) and sodium silicate (SS) immersion (single-stage treatment), and RA treated with mechanical scrubbing and SS immersion in two separate stages (multistage treatment). The subsequent phase of the experimental inquiry involves assessing the physical attributes of both treated and untreated RA. This is followed by conducting microstructural examinations utilizing techniques such as scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and thermogravimetry-differential thermal analysis. The findings indicate that employing a two-step process, involving mechanical abrasion followed by immersion in SS, yields high-quality CRA. This conclusion is reinforced by the favorable physical performance observed. The water absorption values of CRA were lowered by 78 % through single-stage treatments such as immersion in HCl. The similar treatment is found to show densest concrete with calcium/silicon ratio reduced to around 81 % to that of untreated CRA. Additionally, for single-stage treated CRA samples, microstructural study using FTIR verified the creation of additional hydration products, whereas for two-stage treated CRA specimens, thermogravimetric analysis demonstrated the formation of stable CSH. According to the findings, it is advised to use a multistage process of jaw crushing, then treating it with mechanical abrasion and SS. This has the ability to improve the physical, chemical, and microstructural properties of CRA. © © 2024 by ASTM International,
Carbon capture efficiency of ultrafine cementitious substituents and fine aggregate alternatives subjected to accelerated CO2 curing
(Elsevier Ltd, 2025) Trivedi, S.S.; Ansari, F.; Karthik Kumar Goud, P.; Joy, S.; Das, B.B.; Barbhuiya, S.
This manuscript examines the quantification of CO2 uptake, calcium hydroxide (Ca(OH)2, CH) and calcium carbonate (CaCO3, CC) formed for processed recycled concrete fines (RCF), supplementary cementitious materials (SCMs) and various sustainable fine aggregate alternatives subjected to accelerated carbonation process. A thermogravimetric (TG) analyser was used to enumerate the mass loss consequential from these compounds' breakdown at particular temperature range (400–500 °C for CH, 600–800 °C for CC, and CO2). The increased areas of peaks from fourier transform infrared spectroscopy (FTIR) analysis confirmed the presence of calcite and vaterite polymorphs for carbonated RCF and SCMs at 875 cm?1 and 714 cm?1 respectively whereas the formation of calcium silicate hydrate (Ca2.25[Si3O7.5(OH)1.5].8H2O or CSH gel) is confirmed by the increased stretching vibrations of Si-O bond at 970 and 1030 cm?1. The X-ray diffraction (XRD) found the presence of useful compounds such as aragonite, calcium silicate hydroxide (Ca4Si5O13.5(OH)2) and portlandite that further confirmed the carbonation of RCF, SCMs and various fine aggregate alternatives. The formation of these compounds in carbonated specimens resulted in a significant fall in Ca/Si atomic ratio to a maximum of 98 % that further signifies the denseness in microstructure owing to precipitation of CaCO3 and CSH gel deposition. The filled cracks and pores represented by scanning electron microscopy (SEM) images in carbonated specimens demonstrates the suitability of adopted carbonation regimes. The physical performance of RCF, SCMs and various fine aggregate specimens post accelerated carbonation highlights the increase in bulk density, specific gravity and reduced water absorption levels and volume changes that is an area of grave concern for incorporating recycled materials in construction sector. In addition, the CO2 uptake of various carbonated specimens is found using TG analysis demonstrates the highest uptake for RCF at 32.4 % surpassing various other utilised SCMs and fine aggregate alternatives used in the research work. It is to be noted that metakaolin and ultrafine fly ash shows minimal CO2 uptake owing to the manufacturing process. The findings of this study recommend the use of processed RCF and various other SCMs and fine aggregate alternatives for potential carbon dioxide sequestration through accelerated carbonation technology. © 2024 Elsevier Ltd

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