Faculty Publications
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Item 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 Multi-objective optimization of one-part geopolymer mortars adopting response surface method(Elsevier Ltd, 2023) Srinivasa, A.S.; Yaragal, S.C.; Swaminathan, K.; Rakesh Kumar Reddy, R.One-part geopolymers have immense potential in large-scale structures owing to their improved safety and convenience of handling over the conventional geopolymer mixing procedure. Thus, this study aims at optimizing the mixes by assessing the influence of binder content, activator dosage and water to geopolymer solids (W/GS) ratio on the flowability, strength, and shrinkage properties of one-part geopolymer mortars (OPGM). The test results were utilized to develop models that could predict the desired properties of mixes and optimize the mix proportions of OPGMs using the response surface method. The fly ash and slag-based OPGMs were developed. The GGBS substitution was chosen as 25, 50, and 75% by volume of fly ash. The activator dosage was taken as 8, 12, and 16% by mass of total binder content at varied W/GS ratios of 0.35, 0.40, and 0.45. The responses considered were flowability, compressive and flexural strengths at 7 and 28 days, and drying shrinkage of up to 180 days. Total of 504 specimen were cast to record the observations for this optimization study. The GGBS content, W/GS ratio, and combined effect of these factors were found to be the most influential factors affecting the responses. The optimal mix proportion obtained consists of 49.8% GGBS, 13.6% activator dosage, and 0.37 W/GS ratio. This mix achieved 170.4 mm flow, 57.8 MPa and 5.9 MPa compressive and flexural strengths, respectively and also 1626 microstrain of 180 days drying shrinkage. The microstructural characterization adopting techniques like SEM, XRD, TGA and FTIR was carried out to study microstructural changes, mineral phases, thermal mass loss and molecular bonding of OPGM mixes. This study revealed that mix with 50% GGBS, 12% activator dosage and 0.40 W/GS ratio can better be characterized compared to other mixes. © 2023 Elsevier LtdItem Assessment on the effectiveness of chemical admixture in processed laterite and copper slag based geopolymer mortar(Elsevier Ltd, 2025) Clement, D.; C, R.; Singh, S.K.; Tiwari, M.Geopolymer-based cementitious materials known for their robust durability and lower environmental impact make them an ideal choice for sustainable construction. The main focus of this study is to understand the influence of chemical admixtures which plays a pivotal role in improving the properties of geopolymer mortar (GM). This research integrates various chemical admixtures, including calcium chloride, sodium sulphate, sodium hexametaphosphate, and MasterGlenium SKY 8233 (SKY) which falls under the category of either accelerators, retarders, or superplasticisers. Assessments were conducted on the fresh and hardened states of flyash-based GM mixes with varying proportion of river sand (RS), laterite soil (LS) and copper slag (CS), encompassing flowability, setting times, compressive strength, durability study in aggressive environmental conditions and microstructural analyses after 56 days of ambient curing. Findings reveal that calcium chloride and sodium sulphate efficiently decrease the initial and final setting times of the geopolymer paste, highlighting their roles as accelerators, with calcium chloride showing greater efficacy than sodium sulphate. On the other hand, sodium hexametaphosphate serves as a retarder, substantially extending the initial setting time of the geopolymer paste. Introducing the modified polycarboxylic ether (PCE) based superplasticiser SKY into the mortar matrix caused the initial setting time to be extended and resulted in a slight drop in compressive strength compared to the other mixes. Durability tests confirmed the superior resistance of GM mixes to harsh environments like acid, sulphate, and marine water exposure. These findings highlight the potential for tailoring geopolymer blends to achieve desired properties under ambient curing conditions using chemical admixtures. © 2025 Elsevier LtdItem Microstructural insights of geopolymer mortar using binary blended sustainable fine aggregates(Elsevier Ltd, 2025) Clement, D.; C, R.; Agarwal, S.; Pratap, M.The socio-economic growth of a nation depends heavily on the availability of adequate infrastructure, which relies on essential materials like river sand (RS) and cement. However, the rising demand for RS, combined with its excessive extraction causing ecological damage, and its increasing cost, has raised significant concerns. At the same time, the production of cement contributes significantly to environmental damage, especially through CO2 emissions. In this scenario geopolymer technology has emerged as a sustainable alternative to cement, offering environmental benefits and reducing the carbon footprint of construction materials. This study investigates the impact of replacing RS with copper slag (CS) and laterite soil (LS) in geopolymer mortar (GM) on key properties such as setting time, flowability, compressive strength, and microstructure. The results showed that as LS content increased, setting time and flowability decreased considerably, while increasing CS content caused a reduction in these values. Unlike the other observed parameters, the compressive strength values showed no distinct upward or downward trend. Moreover, the microstructural analysis, including SEM, EDS, XRD, FTIR, TGA and BET, provided valuable insights to support the observed results across various mix designs. Overall, the findings highlight that optimised binary blends of CS, LS and RS not only improved the compressive strength but also enhanced the microstructural characteristics of geopolymer mortar, reinforcing their potential as sustainable and high-performance alternatives to conventional fine aggregates. © 2025 The Authors