Abstract
Objective: To analyze the effect of variation of Na2O content on the compressive strength and water absorption of geopolymer paste and mortar specimens. Method: Alkali Activator solution was prepared by mixing sodium silicate solution and sodium hydroxide pellets in appropriate proportions 1 day before its use. The prepared solution was mixed with fly ash (FA) for 5 minutes in Hobart Mixer for geopolymer paste preparation and further sand was mixed to obtain geopolymer mortar. These specimens were placed in a mold and kept in an oven at 48oC for 48 hours. Compressive strength and water absorption tests were conducted on the specimens afterward. In this study, Na2O with 5%, 6.5% & 8.0% was analyzed for its effect on geopolymer paste and mortar.Findings: This research helped in determining the appropriate quantity of NaOH pellets required for geopolymer composite preparation and reducing the cost of construction, as NaOH pellets are more expensive than sodium silicate solution. Maximum compressive strength was achieved by using 8% Na2O content and water absorption was observed maximum at 6% of Na2O content. Novelty: This study is the first of its kind, which has analyzed the effect of Na2O content variation on water absorption and compressive strength of geopolymer paste and mortar specimens. Keywords: Geopolymer composite; compressive strength; water absorption; Sodium Oxide; fly ash
Highlights
Fly ash (FA) obtained from biomass and coal combustion in thermal power plants has been extensively used for the preparation of alkali-activated materials and geopolymer[1]
It is evident from the figure that the compressive strength increases with an increase in Na2O content for both the geopolymer paste and mortars
A significant increase in compressive strength is recorded when the Na2O content is increased to 6.5%
Summary
Fly ash (FA) obtained from biomass and coal combustion in thermal power plants has been extensively used for the preparation of alkali-activated materials and geopolymer[1]. To obtain other binding properties similar to that of the Portland cement (PC), FA is generally mixed with basic alkaline activators such as Na2SiO3, CaO, and NaOH[2] These are a class of mineral binders synthesized by activation of the source materials that could be natural or by-products of the Shukla et al / Indian Journal of Science and Technology 2020;13(38):3994–4002 industries, which has a high content of alumina and silica with an alkali metal hydroxide/ silicate solution at moderate temperatures[3]. These binders have been reported to possess better properties than ordinary Portland cement (OPC) based binders[4]. Molar ratios of Al2O3/ SiO2 if not equals to 3.8 an increase in Na2O content supports the transformation [15]
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