Faculty Publications
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Item Combined effect of marine environment and pH on the impedance of reinforced concrete studied by electrochemical impedance spectroscopy(Springer, 2019) Goudar, S.K.; Das, B.B.; Arya, S.In the present investigation, behavior of OPC and fly ash based concretes were assessed by electrochemical impedance spectroscopy (EIS) technique after exposing the samples to the marine environment in combination with five pH levels (1, 4, 7, 10, and 13). Three different dosages of fly ash (15, 25, and 35%) were used to produce fly ash based concretes. After 90 days of exposure to the aggressive environment, the OPC and fly ash based concretes were tested for impedance analysis and corrosion resistance by electrochemical studies. For the equivalent electrical circuit in EIS study, a total of four electrical circuits were tried for the possible best fit of obtained Nyquist plots. The equivalent electrical circuits proposed by previous researchers failed to provide the best fit for the obtained Nyquist plots. A new equivalent electrical circuit is being proposed in this study which will provide the possible best fit of Nyquist plots when the concrete is being exposed to acidic and alkaline marine environment. It is observed that the pH of the marine environment has a decisive influence on the impedance of reinforced concrete. As the acidity of marine environment reduces to pH 1, the impedance of OPC and fly ash based concrete reduced significantly due to the severe deterioration of concrete composites especially because of acid attack and Cl− ions migration. However, in the case of alkaline nature of the marine environment (pH 13), there was comparably less deterioration of concrete composites which reflected in higher impedance values. The higher dosage of fly ash addition has led to substantial improvement in concrete impedance and also lower corrosion rate. © Springer Nature Singapore Pte Ltd. 2019.Item Characterization of Mechanical and Microstructural Properties of FA and GGBS-Based Geopolymer Mortar Cured in Ambient Condition(Springer, 2021) Prasanna, K.M.; Tamboli, S.; Das, B.B.Fly ash-based geopolymer mortars require heat curing to achieve its properties, which limits its practical application at ambient conditions. The present study was aimed to accomplish the need for application of fly ash-based geopolymers for practical viability without any heat curing by inclusion of ground-granulated blast furnace slag (GGBS). The results revealed that inclusion of GGBS as a partial replacement to fly ash (FA) in geopolymer mortar, which is cured in ambient curing condition, can be able to achieve required setting time and compressive strength. Amalgamation of GGBS with class FA as binder in geopolymerization lend a hand to attain compressive strength as well as setting time which is analogous to ordinary Portland cement (OPC). Microstructural properties were studied using scanning electron microscopy. © 2021, Springer Nature Singapore Pte Ltd.Item Effect of Curing Methods on the Artificial Production of Fly Ash Aggregates(Springer Science and Business Media Deutschland GmbH, 2021) Shivaprasad, K.N.; Das, B.B.; Krishnadas, S.The experimental investigation, provides the results on the artificially produced fly ash aggregates through the pelletization process, is presented in this paper. NaOH and Na2SiO3 were used as alkali activator as a binder. The composition of alkaline solution is maintained as 5% of Na2O and SiO2/Na2O ratio of 0.3 with respect to weight of fly ash used. The detailed investigation is carried out by varying the water content to identify the optimum dosage of water in the alkaline solution in the fly ash pelletization. Further, different methods of curing were investigated to check for the suitable curing method for the production of fly ash aggregate produced. Optimum water content and suitable curing method will be identified through efficiency of pelletization and aggregate properties. Grey relation analysis is performed on the experimental test results to identify the influence of curing method on the produced aggregates. From these results, it is clearly understood that the curing method has significantly improved produced aggregates. © 2021, Springer Nature Singapore Pte Ltd.Item Production of Artificial Aggregates Using Industrial By-Products Admixed with Mine Tailings—A Sustainable Solution(Springer Science and Business Media Deutschland GmbH, 2021) Sharath, B.P.; Das, B.B.This experimental cum research exploration is focused on the production of artificial aggregates with an adoption of pelletization technique. The influential factors for ascertaining the efficiency of the production process are nature of binding agent, required moisture content, process duration and dosage of alkali binder. Aggregates were produced in various combinations including the industrial by-products replaced partially by mine tailings with the addition of some percentages of lime. These produced aggregates were analysed for their engineering properties. It was observed that with the utilization of these mine tailings in this production of artificial aggregates have given an enhancement in the basic characteristic properties of the produced aggregates which are nearly comparable to that of natural aggregates. © 2021, Springer Nature Singapore Pte Ltd.Item Acid, alkali and chloride resistance of high volume fly ash concrete(Indian Society for Education and Environment indjst@gmail.com, 2015) Sahoo, S.; Das, B.B.; Rath, A.K.; Kar, B.B.Objectives: To find variation in compressive strength and mass of high volume fly ash concrete samples subjected to different chemical solutions of sodium chloride, sodium sulphate and sulphuric acid. Methods: A total of 900 numbers of cubes were cast and cured with four levels of curing period of 28, 56, 90 and 120 days. After certain duration of curing period, specific numbers (60) of cubes were submerged each in 5 percent sodium sulphate solution (Na2SO4), 5 percent sodium chloride solution (NaCl) and 1percent of sulphuric acid solution (H2SO4) separately in chemical exposure containers for an exposure period of 30, 60, 90 and 120 days. Findings: Investigations with respect to acid, alkali and chloride resistance were carried out on high volume fly ash concrete, HFC (40 percent replacement with cement), low volume fly ash concrete, LFC (25 percent replacement with cement) and their performances against control concrete (NC) is presented in this paper. Their performance was measured with respect to the loss in compressive strength and weight of the concrete cubes over the period of exposure time. It is found that the resistance of control concrete to all the three chemical attack is better only up to 28 days of water curing. At 56 days of water curing LFC shows better resistance against the control and HFC. However, with prolonged water curing of cubes of 90 days and more, HFC has consistently shown highest resistance; whereas the control concrete faced a great loss in strength.Item Acid, alkali, and chloride resistance of concrete composed of low-carbonated fly ash(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2017) Sahoo, S.; Das, B.B.; Mohammed Mustakim, S.This research investigates the effect of carbonated fly ash inclusion in concrete as partial replacement of cement on the durability performance when exposed to salt, sulfate, and acid solution. The effect of chemical exposure periods (30, 60, 90, and 120 days) on compressive strength and weight of concrete with low volume (25%) replacement of cement was investigated for various water curing ages (28, 56, 90, and 180 days). A comparative assessment with low volume (25% cement replacement) fly ash concrete and control concrete was also conducted. It was observed from the results that low volume carbonated fly ash concrete demonstrated a significant increase in resistance to loss in compressive strength and weight against salt, sulfate, and acid attack. Gray relation-based analysis was performed to determine suitable parameters for simultaneous minimization of strength loss and weight loss under chemical exposure. It can be recommended that, due to its cost-effectiveness, easy processing, and environmental friendly nature, carbonated fly ash can be adopted in construction as a partial replacement of cement in concrete. © 2016 American Society of Civil Engineers.Item Determination of optimized geopolymerization factors on the properties of pelletized fly ash aggregates(Elsevier Ltd, 2018) Shivaprasad, K.N.; Das, B.B.This research investigates the effect of geopolymerization factors on the pelletization in the production of artificial fly ash aggregates. The proportion of pelletized fly ash aggregate mixes was designed through Taguchi's L9 orthogonal array. The properties of the aggregates produced from the optimal mixes were characterized according to the standard specifications. The effect of geopolymerization factors such as Na2O content, water content, and curing regime on the properties of the pelletized fly ash geopolymer aggregates was determined through response indices at the age of 14, 28 and 56 days. In addition, Grey relation based analysis was performed to identify the most critical parameter for optimization among three geopolymerization factors selected in this investigation, for the production of pelletized fly ash geopolymer aggregates. It is observed from the response indices and Grey relation results that the impact value of the aggregates and crushing strength of individual pellets is governed by heat curing and high water content at the age of 14 and 28 days. However, at the age of 56 days these response indices are significantly governed by the solution curing and high water content. It was also noted that the minimum Na2O content of 3.5–4.5% is adequate for the production of pelletized fly ash aggregates. © 2017 Elsevier LtdItem Influence of fineness of fly ash on compressive strength and microstructure of bottom ash admixed geopolymer mortar(Associated Cement Companies Ltd., 2018) Shivaprasad, K.N.; Das, B.B.; Renjith, R.Investigations were conducted to find out the suitability of bottom ash as a possible replacement to fine aggregates in geopolymer mortar. Experimental work was done to study the influence of fineness of fly ash (with three levels of Blaine's fineness, 2043 cm2/g, 2602 cm2/g and 3113 cm2/g on compressive strength and microstructure development of fly ash based geopolymer mortar with natural river sand and bottom ash as fine aggregates. three different water to solids ratios of 0.246, 0.349, and 0.443 were chosen for this study and the curing of the specimens was at ambient temperature (28 ± 3°c). compressive strength development for all eighteen mortar mixes was measured at 7, 14, 28 and 56 days. Further, the effect of fineness of fly ash on degree of polymerization, microstructure and properties of geopolymers was studied using Fourier transform Infrared Spectroscopy (FtIR) and Scanning Electron Microscopy (SEM). It was observed from the compressive strength of the geopolymer mortar that the degree of polymerization is gradual for both types of mortar. there is a continuous increase in the development of compressive strength noticed till the age of 56 days for both types of mortar, sand as well as bottom ash admixed. However, the increment of compressive strength for bottom ash found to be significantly less as compared to natural sand. Improvement in compressive strength due to fineness of fly ash were characterised by SEM and FtIR and it is revealed that with increase in fineness levels, the microstructure significantly enhanced the characteristics of geopolymer mortar. © 2018 Associated Cement Companies Ltd.. All rights reserved.Item Early age, hydration, mechanical and microstructure properties of nano-silica blended cementitious composites(Elsevier Ltd, 2020) Snehal, K.; Das, B.B.; Akanksha, M.This study was carried out to understand the influence of nano-silica on hydration properties of binary, ternary and quaternary blended cement paste and mortar containing micro to nano sized admixtures including fly ash (FA), ultrafine fly ash (UFFA) and nano-silica in colloidal form (CNS). Characterization methods such as thermogravimetric analysis (TGA), X-ray diffraction studies (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) was employed to quantify the hydration products. Further, early age and mechanical properties were also investigated for binary, ternary and quaternary cementitious system blended with nano-silica. The optimized proportions of blended paste and mortar are designed through modified Andreasen and Andersen particle packing model. The experimental test results revealed that the optimum dosage of CNS in binary blended cement composites is 3%. The presence of nano-silica in cementitious system amplified the hydration and pozzolanic activity, thereby promoting densified microstructure at nano scale. The flow test indicated the intensified demand for water absorption and reduced workability with the rise in level of incorporation of CNS particles in cement paste. Quaternary blended mix performed superior hydration along with strength properties amongst all the blended samples. © 2019 Elsevier LtdItem Pozzolanic Reactivity, Hydration and Microstructure Characteristics of Blended Cementitious Composites Comprising of Ultrafine Particles(Springer Science and Business Media Deutschland GmbH, 2022) Snehal, K.; Das, B.B.; Sudhi, A.; Pandey, D.Performance of ultrafine fly ash (UFFA, 5–10 µm) and fly ash (FA, 45–50 µm) particles in cementitious composites was investigated individually as well as in combination. To study the physicochemical behaviour of blended cementitious composites, engineering properties and pozzolanic reactivity test were conducted. Further, characterization techniques such as thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX) were employed. The results showed good amplification in the development of early compressive strength and durability on admixing ultrafine particles of fly ash (UFFA) in cementitious system. Particle size and specific surface area of UFFA greatly influenced on the phase assemblages of cementitious composites, i.e. due to enriched pozzolanic reactivity which reduced Ca/Si atomic ratio (≤ 1.82) in the pore solution of cementitious matrix. On contrary, the presence of UFFA particles in cementitious composite mix developed disjoining pressure in addition to self-desiccation thereby induced early age cracks and also reduced the workability in correspondence to that of FA particles. Further, use of UFFA in conjunction with FA particles, cementitious composites showed much superior performance in terms of both physical and chemical characteristics, which necessitates the crucial need of admixing micron and submicron size particles in the design of sustainable and high-performance cementitious composites at this point of time. © 2022, The Author(s), under exclusive licence to Shiraz University.