Faculty Publications
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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 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 Ltd