Department of Civil Engineering

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Author: search.filters.author.Bhunia, DipenduSubject: search.filters.subject.Civil engineering

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    Sustainable ceramic bricks for toxic industrial waste inertization: factory scale development and characterization
    (Springer, 2025-07) Singhal, Anupam; Routroy, Srikanta; Bhunia, Dipendu
    This work reports factory-scale development of cleaner ceramic bricks with the incorporation of hazardous nickel chromium electroplating sludge (NCS) obtained during chrome-plated steel production. The NCS is particularly rich in chromium and nickel, the two metals used for chrome plating. Earlier attempts to incorporate NCS in ceramic bricks faced substantial strength reduction due to heavy metals’ presence. We engineered a high-volume incorporation of pulverised coal fuel ash (PFA) along with NCS and tested 20 compositions with varying proportion of the three ingredients. The optimum composition was obtained with 37.5% PFA, 12.5% NCS, and remaining clay soil. The optimum composition bricks witnessed substantially enhanced density and compressive strength, reduced water absorption and efflorescence. XRD analysis indicated formation of spinel structure and mullite leading to strength enhancement. SEM analysis indicated increased pore filling in brick matrix with PFA cenospheres. XRF analysis revealed appreciable presence of fluxing oxides in NCS which facilitated the sintering process. Additionally, higher amount of reactive silica and alumina in PFA led to formation of stronger ceramic bonds. Leaching tests by Toxicity Characteristic Leaching Procedure indicated negligible release of heavy metals, indicating successful immobilization of heavy metals. The developed methodology provides the relevant stakeholders an eco-friendly, economical, readily deployable scheme for eliminating the mounting NCS accumulation.
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    Structural health monitoring based on aggregation-induced emission active mechanoluminescence organic material
    (AIJR, 2025-03) Bhunia, Dipendu
    The current research aims to design a stress sensor using a recently synthesized organic molecule that exhibits a mechanoluminescence (ML) property. The experimental set-up is established by analyzing different application techniques and modes of capturing real-time emission along with compound and structural material interaction with other molecules. From the implemented experimentations, it was assessed that the emission color and intensity changed when applying axial pressure (direct) and showed the reversible property. This unique attribute contributed by the organic molecule shows the opportunity to develop real-time sensing and non-destructive evaluation methods of structural health monitoring.
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    Synergic valorization of nickel-chrome plating sludge via alkali activation of steel slag and fly ash: performance analysis
    (Springer, 2024-09) Lahoti, Mukund; Singhal, Anupam; Routroy, Srikanta; Bhunia, Dipendu
    Nickel–chromium plating sludge (NCPS) is a hazardous waste due to high concentration (~ 25%–30%) of chromium and nickel. Electric arc furnace slag (EAFS) is a by-product of secondary steel manufacturing through the electric arc furnace route. In this work, we valorized NCPS in an innovative ambiently cured alkali-activated NCPS-Fly ash-EAFS mortar (ANFEM). NCPS substituted the binder from 0 to 25% (by weight) in the step size of 5%. The binder composition had EAFS/fly-ash = 1.0, activator/binder = 0.45, silicate/hydroxide = 2.5. Incorporation of NCPS in ANFEM resulted in several benefits such as successful NCPS immobilization, improving the flash setting and flowability issues of alkali-activated EAFS and minimal degradation in mechanical properties. Microstructural investigation by XRD, FTIR, SEM offered insights on the underlying mechanisms of NCPS valorization and corroborated the observed results of compressive strength, water absorption, bulk density, acid resistance, and surface porosity test. At 10 wt% substitution of NCPS, ANFEM produced optimum results, such as compressive strength of 40 MPa; Wabs enhancement by 4.2%; bulk density reduction by 1.1%; and the least acid-induced deterioration. Extensive leaching tests determined leachate’s heavy metals concentration to be well-within the permissible limits. Factory scale deployment of developed methodology produced paver blocks well-satisfying Indian Standard Code 15,658: 2006.
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    Optimization of sandstone processing waste, electric arc furnace slag, and fly ash-based ternary blended eco-friendly geopolymers
    (Springer, 2024-11) Bhunia, Dipendu; Chakraborty, Sayantan; Lahoti, Mukund
    Over the years, ordinary Portland cement (OPC) has been used to meet growing demands of land and housing facilities arising out of population overburdens. It is well documented that OPCs, besides their outstanding qualities as building materials, are also significant contributors to global greenhouse gases (GHG). Consequently, recent years have noticed an emerging interest in the search for alternatives to Portland cement-based binders. Geopolymers are well-suited to serve this purpose owing to their superior attributes and low CO2 emissions compared to conventional cement. Still, the industrialization of geopolymers has not reached a meaningful value due to the prevailing fundamental barriers involving the requirement of corrosive environments and intensive heat-curing regimes in post-fabrication processes. The current study investigates the viability of using synergistic mixtures based on stone residues, pulverized ash, and steel slags in fabricating geopolymer composites cured at ambient temperature with reduced ingestion of alkalis. A comprehensive assessment of the engineering, mineralogical, and microstructural characteristics was performed in terms of setting times, physico-mechanical, durability, non-destructive, and analytical tests. Further, a scaled-down approach was utilized to evaluate the feasibility of the designed composites as construction entities. The incorporation of SW (10–40%) prolonged the setting periods (~ 150 min.) and abridged the engineering properties of the ternary pastes collectively by 127% due to silica coalescences. Besides, replacements of stone residues with FA (20–30%) and EAF (30–60%) improved the blend performance due to Ca and Al assimilations. All the developed composites satisfied the acclamations for OPC grade 33, CEM V class 32.5N, and OPC Type – I suggested by IS, EN, and ASTM standards, respectively, with matrices constituting CASH-CSH-NASH-(N,C)-A-S–H type gelation complexes identified by the X-ray, infrared, and electron imaging spectroscopic analysis. In addition, a cumulative deficit of about 60–90% was observed in energy and carbon footprints relative to OPCs, indicative of the binders’ sustainability traits.