Faculty Publications
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Item Swell-Compressibility Behavior of Geopolymer Blended Expansive Clays(Springer Science and Business Media Deutschland GmbH, 2021) Thotakura, V.; Sunil, B.M.; Chaudhary, B.This paper presents the influence of GGBS-based geopolymer on swell-compressibility characteristics of oven-dry, expansive clay passing 4.75 mm sieve. One-dimensional swell-consolidation tests were conducted on the expansive clay passing through 4.75 mm sieve to which GGBS was added at 0, 5, 10, 15, and 20% by dry weight of the clay. Rate of heave, swell potential, swelling pressure, and linear shrinkage were evaluated. Rate of heave and swell potential decreased significantly with increase in GGBS content. The paper also explores the microstructure behavior and surface texture of the GGBS-based geopolymer–clay blends using the scanning electron microscopy (SEM). The SEM results revealed that the higher Si/Al compounds increase the dense phase of geopolymer products. Moreover, geopolymer synthesis can contribute to the bulk utilization of industrial by-products. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Study on the strength parameters of high volume fly ash concrete and geopolymer concrete(2011) Shetty, A.; Anand, V.R.; Hegde, P.Concrete has been the most preferred construction material. It is being increasingly used day by day all over the world due to its versatility, mould ability and high compressive strength. But the large-scale production of cement is causing environmental problems on one hand and the unrestricted depletion of natural resources on the other. So the issue of sustainable development in concrete construction is addressed in this paper through development of concrete mixes by replacing certain percentage of cement with fly ash. Trials on concrete mixes with replacement of 40%, 50%, 60% and 70% of cement with fly ash are carried out and the results depict that at the replacement level of 40% cement by fly ash, the required strength is achieved. It is also observed that the rate of early strength gain is retarded as the percentage replacement of cement increases. But in case of Geopolymer concrete (100% replacement of cement by fly ash) under a curing temperature around 600C and above, the strength gain rate is very high in initial stages. It is observed that design strength is achieved within 28 hours of oven curing. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Enhancement of the properties of fly ash based geopolymer paste by incorporating ground granulated blast furnace slag(Elsevier Ltd, 2017) Saha, S.; C, C.Research efforts have been made continuously to establish fly ash based geopolymer as an alternative binder material for the production of fresh concrete because production of Ordinary Portland Cement degrades the environment by huge emissions of carbon-di-oxide and also by consuming lot of natural resources. But most of the study reveals, fly ash based geopolymer paste needs more time to get set when it is cured at ambient temperature. As a result, it is quite impractical to use fly ash based geopolymer paste as an alternative to Ordinary Portland Cement in faster construction. In this study, an effort has been made to enhance the properties of fly ash based geopolymer paste by incorporating ground granulated blast furnace slag at various percentage levels. Microstructure of the geopolymer paste is studied using Scanning Electron Microscopy. Result of this investigation shows that significant improvement on setting time and compressive strength can be obtained by adding ground granulated blast furnace slag in the mixes. © 2017 Elsevier LtdItem 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 Investigation on the potential use of recycled fine aggregate to produce geopolymer mortar mix(ASTM International, 2019) Saha, S.; C, C.The utilization of construction and demolition waste (C&DW) partially or fully for various purposes in construction industries is one of the most significant solutions to overcome the scarcity of raw materials and disturbances of the environmental system. On the other hand, geopolymer is being tried to be established as an alternative sustainable binder material for ordinary portland cement. In the present study, with the thought of promoting of sustainability, an attempt has been made to use concrete wastes as recycled fine aggregate (RFA) partially to produce fly ash (FA)-based geopolymer mortar. The workability, water absorption, compressive strength at 3, 7, 28, and 56 days, volume change behavior, and chloride permeability of the produced FA-based geopolymer mortar were determined. The effects of RFA, the ratio of alkali liquid (AL) to FA, and different curing regimes on these properties of mortar mix also discussed. The morphology and microstructures of the samples taken from the mortar mix, which were observed having the highest strength under different curing regimes, were studied using scanning electron microscopy (SEM). The experimental results indicate lower workability, higher water absorption capacity, and higher drying shrinkage of geopolymer mortar mix that has more RFA content in the mix, but the compressive strength of the geopolymer mortar mix started decreasing after a certain percentage of RFA content in the mix. Utilization of that certain percentage of RFA will help us to minimize the consumption of natural fine aggregates and reduce the disturbances generated by unorganized dumping of C&DW. © 2019 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.Item Volume change characteristics of eco-friendly mortar mixes produced with geopolymeric binder and recycled fine aggregate(ASTM International, 2020) Saha, S.; Shaik, N.; C, C.The production of geopolymer mortar using recycled fine aggregate (RFA) generated from concrete waste has significant potential to be a sustainable construction material. In this article, the volume change properties of the produced geopolymer mortar mixes are studied in terms of drying shrinkage up to the age of 180 days and reported as the percentage increase with respect to the shrinkage value of 3 days. The influence of RFA content, alkaline liquid (AL) in terms of the concentration of sodium hydroxide (SH) solution, the ratio of sodium silicate (SS) solution to SH solution, and the ratio of AL to fly ash (FA) were investigated on the drying shrinkage properties of the geopolymer mortar mixes. All the cast specimens were cured at 80°C for 24 hours. Higher drying shrinkage values were observed for the mortar mixes produced with higher RFA content, AL/FA, SS/SH ratio, and lower concentration of SH solution. Scanning electron microscope images were studied for the samples taken from the geopolymer mixes showing lower drying shrinkage values to understand the microstructure. © 2019 by ASTM International.Item Strength and shrinkage properties of heat-cured fly ash-based geopolymer mortars containing fine recycled concrete aggregate(ASTM International, 2020) Saha, S.; C, C.Geopolymer has obtained significant importance as an alternative eco-friendly binder material for ordinary portland cement (OPC) as it can be produced from the reaction between the industrial by-product materials rich in alumina, silica, and alkaline solutions. Therefore, usage of geopolymer effectively in the construction industry will help to reduce the consumption of a huge quantity of natural resources for the energy processes required for the production of OPC. It is also one of important solution to control carbon dioxides emission by the usage of OPC. On the other hand, using construction and demolition waste (C&DW) as the source of recycled aggregates in construction industry helps to reduce the huge consumption of natural aggregates and protect the environment from the disturbances caused by the unorganized dumping of C&DW. In this study, an attempt has been madeto produce fly ash (FA)-based geopolymer mortar mixes using C&DW effectively as fine aggregates partially. The effects of recycled fine aggregates (RFA), the ratio of alkaline liquid (AL) to FA, and duration of heat curing on the properties of the produced geo-polymer mortar mixes have been discussed in this article. To determine the influence of RFA on the strength and volume change behavior of mixes, natural fine aggregates were replaced by RFA at 0, 10, 20, 30, 40, and 50 % by mass. The AL/FA ratio was adopted as 0.4 and 0.6. Higher compressive strength was observed for most of the mortar mixes having RFA up to 20 %, and higher drying shrinkage value was found for the mixes with higher RFA content. Scanning electron microscopy (SEM) images were also studied for knowledge about the signature of the formed structures in the mortar mixes, which were observed having higher strength. © © 2019 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.Item Effect of Chloride on Accelerated Corrosion of Steel Rebar in Alkali-Activated Fly Ash and Paper Sludge Ash–Reinforced Concrete(Electrochemical Science Group, 2022) Senthamilselvi, P.; Palanisamy, T.; Senthil Kumar, S.The aim of this work was to investigate the corrosion of reinforcing rebar inserted in geopolymer concrete (GPC) made from fly ash (FA) containing 10% paper sludge ash (PSA) by weight under three curing conditions, namely oven curing (OC) at 60°C, external exposure curing(EEC), and curing at ambient temperature (AC). The investigation was carried out on the GPC using linear polarization resistance and Tafel plot techniques. All of the reinforced lollipop specimens were stored in a 3.5% NaCl solution with a steady anodic electrical potential of about 12 V applied to accelerate the corrosion process. Both the bond strength loss percentage and the mass loss percentage of the corroded steel rebar embedded in the concrete cylinder specimens were calculated. The test results showed that the OC condition demonstrated best corrosion resistance in the FA-GPC specimen compared to the FA-PSA GPC specimen. The test results for FA-PSA GPC specimens showed that their corrosion resistance performance was better under AC condition compared to the other two curing conditions. © 2022 The Authors. Published by ESG (www.electrochemsci.org). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/4.0/).Item Effect of slag and solid activator on flowability and compressive strength of fly ash based one-part geopolymer pastes(Elsevier Ltd, 2023) Srinivasa, A.S.; Swaminathan, K.; Yaragal, S.C.The geopolymerization process has led to the transformation of industrial by-products into sturdy and long-lasting construction materials, such as geopolymer binders, which can be used to mitigate the massive CO2 emissions associated with the production of Ordinary Portland Cement (OPC). These binders are produced from aqueous solutions of alkali activators and alumina and silica rich industrial waste materials. Strong, caustic, and viscous aqueous solutions are used in alkali activation. Its handling, usability, and mass production are all tough, even transport and site difficulties compound these issues. The solid alumina-silica rich components, solid alkali activators, and free water are dry mixed in this work to create a unique “one-part” or “simply add water” geopolymer binder that is equivalent to OPC in its manufacture. Researchers looked at the flowability and compressive strength properties of fly ash based one-part geopolymer mixes while adding ground granulated blast furnace slag and a solid activator (anhydrous sodium metasilicate powder). At the 25 and 50% replacement levels, GGBS was used in place of fly ash. Solid activator content varied from 8 to 16% at an interval of 2% for each replacement level of GGBS. Microstructural and mineralogical alterations were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. According to the findings of the tests, the flowability and compressive strength improved with decreasing slag and solid activator concentration. It was found that activator content increments beyond 12% result in minor reduction in compressive strength, and that the highest compressive strength was measured at 50% GGBS and 12% activator content. Both flowability and compressive strength were improved by the 50% GGBS and 12% activator mixture, which also displayed symptoms of having a dense and compacted microstructure. © 2023