Faculty Publications

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Author: search.filters.author.Das, B.B.Subject: search.filters.subject.Concrete aggregates

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    Pelletisation factors on the production of fly-ash aggregates and its performance in concrete
    (ICE Publishing, 2023) Shivaprasad, K.N.; Das, B.B.; Sharath, B.P.
    This research study investigates the factors associated with pelletisation in the production of fly-ash aggregates and its performance in concrete. To investigate this influence, experiments were carried out in different stages to explore the effect of factors responsible for pelletisation, which were designed through Taguchi’s experimental design. Additionally, the influence of each parameter on the engineering properties of the produced aggregates was determined using Grey relational analysis. Further, considering the optimised pelletisation factors of the laboratory-scale studies and with the help of an industrial-scale pelletiser, mass production of fly-ash aggregates was carried out and characterised for their engineering properties. The test results indicate that these aggregates are mainly governed by water content followed by the angle and speed of pelletizing disc. It is observed from the results that the engineering properties of aggregates produced on an industrial scale are found to be better than sintered aggregates and also comparable with that of natural aggregates except for water absorption. The properties of concrete produced with fly-ash aggregates, light weight sintered aggregates and natural aggregates were also studied. The results showed that properties of concrete produced with fly-ash aggregates are in good correlation with those of conventional concrete produced with natural aggregates. © 2023 ICE Publishing. All rights reserved.
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    Influence of multi-stage processing and mechano-chemical treatments on the hydration and microstructure properties of recycled aggregate concrete
    (Elsevier Ltd, 2023) Trivedi, S.S.; Sarangi, D.; Das, B.B.; Barbhuiya, S.
    On account of the shortage of naturally occurring coarse aggregate, recycled aggregate (RA) made from crushed concrete debris is now used in the construction industry. With this rise in the utilisation of recycled aggregate in the construction sector, there has been extensive research into ways to improve its quality. The significant fraction of mortar remains that are left on the RA surface is the primary factor that affects its quality. Concrete made from RA loses strength and mechanical performance due to the attached mortar's increased porosity and water absorption values and the frailer transition region between the new mortar and aggregates. In order to minimise the old cement fractions and increase the quality, this paper studies the effect of concrete incorporating multi-stage processed RA from demolished concrete waste, followed by treatment with mechanical abrasion and sodium silicate immersion. The recycled aggregates were produced through multi-stage jaw crushing, followed by utilising natural aggregate, recycled aggregate, and recycled aggregate obtained after mechanical abrasion, followed by sodium silicate treatment for concrete mix design at various substitution percentages as coarse aggregates. The experimental investigation further progresses with the evaluation of mechanical and durability properties of concrete mixes, which is additionally followed by microstructural studies such as scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDAX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Thermogravimetry-differential thermal analysis (TG-DTA). The outcomes demonstrate that two-stage treatment, such as mechanical abrasion followed by sodium silicate immersion, yields superior-quality RA. Recycled aggregate concrete (RAC) made with these treated aggregates illustrated an increase in workability and density with respect to an untreated RAC mix. Furthermore, comparable strengths in compression, flexure, and tension are found in treated RAC mixes, particularly at 35% replacement levels, with respect to concrete mixes comprised of natural aggregates. A similar trend is detected in the chloride penetration tests and water sorptivity tests. In addition, the microstructural investigation confirmed the formation of additional calcium silicate hydrate for treated RAC mixes, particularly for the 35% substituted RA mix. On the basis of the results, it is suggested that multi-stage jaw crushing followed by treatment through mechanical abrasion and sodium silicate can potentially enhance the mechanical, microstructural, and durability performance of RAC. © 2023 Elsevier Ltd
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    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,
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    Performance of construction and demolition waste as recycled aggregates in concrete - Review
    (ICE Publishing, 2024) Trivedi, S.S.; Das, B.B.; Barbhuiya, S.
    This article presents a structured and comprehensive review of the existing literature on physical, chemical, microstructure, and durability properties of recycled aggregate concrete (RAC). The engineering properties of concrete made from such recycled aggregates are critically analysed by focusing mainly on the fresh and hardened states along with several characterisation techniques such as scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetry/differential thermal analysis. Also, creep, shrinkage, microstructure and durability of RAC were evaluated critically. In addition, improvement techniques in its microstructure are also explored with efficient mixing approaches for the development of geopolymer RAC. Furthermore, techniques to enhance the mechanical characteristics and long-term performance of recycled aggregate are distilled and divided into three categories: (1) lowering the porosity of recycled aggregate, (2) lowering the layer of old mortar on the surface of recycled aggregate, and (3) enhancing the property without changing the recycled aggregate. It is evident from the thorough examination that recycled aggregates can be used in concrete up to a certain amount. For the creation of sustainable and high-performance concrete, it is also necessary to incorporate mineral admixtures of micron, sub-micron, and nano size to address the drawbacks of recycled aggregates. © 2025 Emerald Publishing Limited: All rights reserved.
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    Performance characteristics of self-compacting concrete containing lateritic fine aggregate as a partial replacement to natural river sand
    (Institute of Physics, 2024) Kiran Bhat, K.; C, C.; Das, B.B.
    This study identifies the use of processed lateritic fine aggregate (LFA) as a sustainable material for the replacement of natural fine aggregate (NFA) in self-compacting concrete (SCC). Cubes were cast with LFA replacements from 10% to 80% with an interval of 10% for checking the compressive strength development at 28 and 90 days. The findings demonstrate that the replacement of 30% NFA with LFA leads to the optimum performance, resulting in compressive strengths of 45.5 MPa and 53 MPa after 28 and 90 days of curing. Similar trends are also noted with the specimens cast for splitting tensile and flexural strengths as per IS 516: 2021. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Thermogravimetric analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR) were performed to understand the surface morphology, material characterization, and composition differences between the control mix (C30F) and optimized lateritic SCC (C30F30L). SEM and EDX analysis demonstrated the contribution of the introduced fly ash particles to the strengthening of concrete. TGA with DTA has shown the more complicated denser structure of the C30F mix, and FTIR has confirmed the presence and formation of the C-S-H gel. Si-O-Si asymmetric stretching band has extra peaks, and with FTIR, O-C-O asymmetrical bending and stretching wave band have a lower intensity than the C30F mix due to the partial replacement of LFA. In addition, it is also observed from the durability studies that C30F30L showed an increase in pore volume and capillary pore network compared to C30F mix. © 2024 The Author(s). Published by IOP Publishing Ltd.
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    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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    Enhancing sustainability with ternary blended cement and fine aggregate in self-compacting lateritic concrete with supplementary materials
    (Elsevier Ltd, 2025) Kiran Bhat, K.; C, R.; Das, B.B.
    This study explores an innovative approach to sustainable self-compacting concrete (SCC) by partially replacing natural fine aggregate (NFA) with lateritic fine aggregate (LFA) and manufactured sand (M-sand). Additionally, fly ash and ultrafine ground granulated blast furnace slag (UGGBS) were introduced as supplementary cementitious materials to enhance performance. Fresh properties of the SCC mixes met as per Indian standards, demonstrating satisfactory flowability, passing ability, and stability. Among the mixes, the combination of 30 % fly ash (30 F), 30 % LFA (30 L) and 50 % M-sand (50 M) replaced in the conventional SCC mix, designated as C30F30L50M, exhibited optimal workability and segregation resistance. Mechanical tests revealed improvements in long-term strength, with the optimized mix containing 5 % UGGBS showing superior flexural strength at 90 days. Durability assessments indicated increased water absorption in mixes containing LFA and M-sand, while the control mix displayed better resistance to chloride penetration. Microstructural analyses (SEM, XRD, TGA/DTG, and FTIR) confirmed enhanced hydration and phase development influenced by the blend of fine aggregates and supplementary materials. The findings highlight the potential of utilizing LFA and M-sand in SCC to achieve sustainable concrete with improved performance characteristics. © 2025 The Authors
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    Effect of CO2 curing on phase compositions of nano silica blended cementitious mortar partially replaced with carbonated recycled fine aggregates
    (Elsevier Ltd, 2025) Trivedi, S.S.; Ansari, F.; Das, B.B.; Barbhuiya, S.
    This manuscript examines the quantification of CO2 uptake, hydration and carbonation phases such as calcium hydroxide (Ca(OH)2, CH), calcium carbonate (CaCO3, CC), magnesite (MgCO3), hydromagnesite (MgCO3.Mg(OH)2.4H2O, Hmgs), siderite (FeCO3) and subsequent carbonation and hydration degrees (CD, HD) in cementitious mortar (CM) incorporating colloidal nano silica (CNS) and carbonated and uncarbonated recycled concrete fine aggregates (RCF) subjected to accelerated carbonation curing (carbonated RCF- CRCF, Non-carbonated RCF- NCRCF). The RCF was prepared through multi cycle jaw crushing technology followed by repeated abrasion cycles and subsequently treated using accelerated carbonation. The mass loss resulting from the breakdown of these compounds at specific temperature ranges (220–350 °C for Hmgs, 250–400 °C for FeCO3, 400–500 °C for CH, 460–900 °C for MgCO3, and 600–800 °C for CC and CO2) was calculated using a thermogravimetric (TG) analyzer. The main findings of this research work confirms the presence of vaterite, calcite, tobermorite (Ca2.25[Si3O7.5(OH)1.5].8H2O or CSH gel), and magnesite polymorphs for CM incorporating 6–9 % CRCF and 1 % CNS as validated by the increased areas of peaks from fourier transform infrared spectroscopy (FTIR) analysis at 714 cm?1, 875 cm?1, 1007 cm?1, and 1405 cm?1, respectively which is further recognized by the increased peak intensities in X-ray diffraction (XRD) analysis. The important findings from the scanning electron microscopy (SEM) analysis revealed the development of additional C-S-H and calcite phases filling the pores and densifying the matrix in CRN mixes while the Ca/Si atomic ratio significantly decreased up to 67 % for CRN-19 mix as found by the energy dispersive X-ray spectroscopy (EDAX). The fresh and hardened state properties of blended mixes highlight the increase in dry density and compressive strength that are found maximum for CRN-19 mix of 57.9 MPa at 28 days owing to the highest rate of strength contribution of 27.95 % from the mix components such as 9 % CRCF and 1 % CNS. However, the flowability is observed to get reduced for all the mixes with CRN-13 mix illustrating approximately 83 % flow values with reference to the control mix. Furthermore, the durability performance of CRCF based primary mixes and all the secondary blends are found to show lowest ingress of chloride ions and permeable porosity values, illustrating up to 73 % and 39 % fall respectively to that of control mix at 28 and 56 days cured samples. Based on the comprehensive investigation and analysis, it is recommended to use pre-carbonated RCF and CNS for developing sustainable CM and achieving CO2 sequestration. © 2025 Elsevier Ltd