Abstract
In this study, an attempt has been made to study the effect of alkali activator on the standard consistency and setting times of low calcium fly ash (FA) and ground granulated blast furnace slag (GGBS)‐ based sustainable geopolymer pastes. Different proportions of FA and GGBS were blended into mixes of geopolymer paste using sodium hydroxide (SH) and sodium silicate (SS) as alkaline activator solution (AAS). Tests on geopolymer pastes for consistency and initial and final setting times were carried out for three different SH : SS ratios of 1 : 1, 1 : 2, and 1 : 3 for both 2.5 M (molarity) and 5.0 M of SH concentration. While increasing the molarity of SH, both consistency and setting time decreased. For all the blended binder mix, the setting time decreases with an increase in the quantity of SS in the alkali activator solution. An increase in the amount of GGBS content in the geopolymer blended binder mix increases the consistency and decreases the setting time. For both 2.5 M and 5 M blended geopolymer mixes, a decrease in the percentage of GGBS and an increase in the percentage of FA increased the setting time. Microstructural studies such as X‐ray fluorescence analysis (XRF), X‐ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT‐IR) analyses were carried out, and the results are presented. The FT‐IR spectra for the blended binder mixes demonstrated the formation of geopolymerization and the presence of the functional groups.
Highlights
Cement as a binder material plays a vital role in building construction
This research addresses two issues: (i) effect of alkali activator on the standard consistency and setting times of geopolymer concrete and (ii) use of fly ash (FA) and ground granulated blast furnace slag (GGBS), the industrial by-products in producing geopolymer concrete
The mineral admixtures such as FA, GGBS, metakaolin, and rice husk ash can be used in concrete to replace the cement to obtain concrete with better performance and good engineering properties [11]
Summary
Cement as a binder material plays a vital role in building construction. Cement is used in all construction works either as a plaster or as an ingredient in producing concrete. This research addresses two issues: (i) effect of alkali activator on the standard consistency and setting times of geopolymer concrete and (ii) use of FA and GGBS, the industrial by-products in producing geopolymer concrete. Binders could be produced by a polymeric reaction of alkaline liquids with silicon and aluminium in source materials of the byproducts such as FA, GGBS, and rice husk ash [5, 10] The mineral admixtures such as FA, GGBS, metakaolin, and rice husk ash can be used in concrete to replace the cement to obtain concrete with better performance and good engineering properties [11]. Due to this alkaline solution, an aluminosilicate reaction has been triggered, leading to the formation of geopolymer concrete and corresponding hydroxides These products have undergone a polymerization reaction through gel formation, where hardening of materials takes place. Setting times of low calcium FA and GGBS- based sustainable geopolymer pastes
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