Faculty Publications
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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 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 Performance of eco-friendly mortar mixes against aggressive environments(Techno-Press info@techno-press.com, 2020) Saha, S.; C, C.; Gupta, P.Past research efforts already established geopolymer as an environment-friendly alternative binder system for ordinary Portland cement (OPC) and recycled aggregate is also one of the promising alternative for natural aggregates. In this study, an effort was made to produce eco-friendly mortar mixes using geopolymer as binder and recycled fine aggregate (RFA) partially and study the resistance ability of these mortar mixes against the aggressive environments. To form the geopolymer binder, 70% fly ash, 30% ground granulated blast furnace slag (GGBS) and alkaline solution comprising of sodium silicate solution and 14M sodium hydroxide solution with a ratio of 1.5 were used. The ratio of alkaline liquid to binder (AL/B) was also considered as 0.4 and 0.6. In order to determine the resistance ability against aggressive environmental conditions, acid attack test, sulphate attack test and rapid chloride permeability test were conducted. Change in mass, change in compressive strength of the specimens after the immersion in acid/sulphate solution for a period of 28, 56, 90 and 120 days has been presented and discussed in this study. Results indicated that the incorporation of RFA leads to the reduction in compressive strength. Even though strength reduction was observed, eco-friendly mortar mixes containing geopolymer as binder and RFA as fine aggregate performed better when it was produced with AL/B ratio of 0.6. © 2020 Techno-Press, Ltd.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 Compressive strength prediction of SCC containing fly ash using SVM and PSO-SVM models(Structural Engineering Research Centre, 2021) Rajeshwari, R.; Mandal, S.; C, C.Self-Compacting Concrete (SCC), is a highly workable material, compacted by its self weight without observable segregation and bleeding. In this study, Support Vector Machine (SVM) and particle swarm optimization based SVM models are employed to predict the 28 days compressive strength of individual SCC mix. A database of 62 no’s of SCC compressive strength from literature with cement partially replaced by fly ash is used for training the models. The test data consists of two groups, an individual study consisting of 9 datasets and other combination of three studies with 19 datasets tested separately. Similar input parameters from the train data is extended for testing the models prediction accuracy. Statistical parameters such as correlation coefficient, root mean square error and scatter index are used to evaluate the models’ prediction results. The particle swarm optimization based SVM model is capable of selecting appropriate SVM parameters to increase the prediction accuracy. From the results, it is seen that both SVM and particle swarm optimized SVM models have good capability in predicting the SCC compressive strength. © 2021, Structural Engineering Research Centre. All rights reserved.Item PERFORMANCE ASSESSMENT OF STEEL SLAG AGGREGATES AS PARTIAL REPLACEMENT OF RIVER SAND IN CONCRETE(Associated Cement Companies Ltd., 2023) Sundaramoorthi, S.; Hemalatha, T.; C, C.In order to bring sustainability in construction, nowadays, many industrial solid wastes are used as a partial replacement for cement as well as aggregates. Using industrial wastes in construction solves dual problem of waste disposal and depletion of natural resources. Steel aggregate is one such industrial solid waste having potential to replace the conventional river sand. In this study, an attempt has been made to investigate the performance of steel slag aggregates in concrete as a partial replacement for conventional river sand. Three mixes were made for this study, first mix made of ordinary Portland cement (OPC) and 100 % river sand (0M0), second mix (0M50) made of OPC and 50 % river sand replaced by slag aggregates and third mix (25M50) made of 25 % fly ash and 75 % OPC, and 50 % slag aggregates. Tests for assessing the mechanical and durability properties were conducted. The results showed that the strength and durability of concrete made with steel slag aggregate and river sand were comparable. This study shows the suitability of using 50% steel slag aggregates as a partial replacement for river sand in concrete. © 2023, Associated Cement Companies Ltd.. All rights reserved.Item Performance and microstructural investigations of processed lateritic fine aggregates in blended cement mortars exposed to elevated temperatures(Emerald Publishing, 2023) Basavana Gowda, S.N.; Yaragal, S.C.; C, C.; Goudar, S.K.Purpose: In recent years, fire accidents in engineering structures have often been reported worldwide, leading to a severe risk to life and property safety. The present study is carried out to evaluate the performance of Ground Granulated Blast Furnace Slag (GGBS) and fly ash–blended laterized mortars at elevated temperatures. Design/methodology/approach: This test program includes the replacement of natural river sand with lateritic fine aggregates (lateritic FA) in terms of 0, 50 and 100%. Also, the ordinary Portland cement (OPC) was replaced with fly ash and GGBS in terms of 10, 20, 30% and 20, 40 and 60%, respectively, for producing blended mortars. Findings: This paper presents results related to the determination of residual compressive strengths of lateritic fine aggregates-based cement mortars with part replacement of cement by fly ash and GGBS exposed to elevated temperatures. The effect of elevated temperatures on the physical and mechanical properties was evaluated with the help of microstructure studies and the quantification of hydration products. Originality/value: A sustainable cement mortar was produced by replacing natural river sand with lateritic fine aggregates. The thermal strength deterioration features were assessed by exposing the control specimens and lateritic fine aggregates-based cement mortars to elevated temperatures. Changes in the mechanical properties were evaluated through a quantitative microstructure study using scanning electron microscopy (SEM) images. The phase change of hydration products after exposure to elevated temperatures was qualitatively analyzed by greyscale thresholding of SEM images using Image J software. © 2023, Emerald Publishing Limited.Item Influence of the mix parameters on shrinkage properties of environment-friendly mortar(Taylor and Francis Ltd., 2024) Saha, S.; C, C.Cracks in concrete structures are generally initiated due to the shrinkage i.e. the volume change characteristics of the concrete structures. In this experimental study, effects of the mix parameters related to alkaline liquid (AL) and recycled fine aggregate (RFA) on the shrinkage behaviour of environment-friendly mortar mixes produced with fly ash (FA)-based geopolymer binder and RFA were investigated and reported. To find out the effects of AL, concentration of liquid sodium hydroxide (LSH) was varied from 6M to 16M, ratio of liquid sodium silicate (LSS) to LSH in AL was varied from 1.0 to 2.5 and AL/FA ratio was considered as 0.4 and 0.6. Different fly ash-based geopolymer mortar mix were produced depending on above-said combinations of mix parameters along with the RFA content (by weight) of 10%, 20%, 30%, 40% and 50% in lieu of natural fine aggregate. Prismatic specimens (25 mm × 25 mm × 285 mm) were cast and cured at ambient air temperature to determine the shrinkage behaviour. Higher RFA content in mix, higher LSS/LSH ratio in AL and higher AL/FA ratio resulted in higher shrinkage value. But, lesser shrinkage value was noticed for those specimens of mortar mix with the consideration of higher concentration of LSH in AL with varying RFA content. ©, Engineers Australia.