Abstract
This study describes the synthesis at ambient temperature (25±3 °C) of binary geopolymer systems based on natural volcanic pozzolan and granulated blast furnace slag. Na2SiO3 and NaOH were used as alkaline activators. The effects of the SiO2/Al2O3, Na2O/Al2O3 ratio and the amount of slag added (from 0 to 30%) on the reaction kinetics, compressive strength and microstructure of the final product were studied. To characterise the geopolymer pastes, techniques such as X-ray diffraction (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used. The results indicate the possibility of obtaining a geopolymer cement with a compressive strength of up to 48.11 MPa after 28 days of curing at ambient temperature whose characteristics are comparable to those of commercial portland cement.
Highlights
Geopolymers are a group of cementing ceramic materials belonging to the family of inorganic polymers that are obtained from the reaction between an aluminosilicate and one alkaline activator
These challenges have incentivised the development of studies focused on the production of alkaline activation cements based on different natural resources, such as clays and natural pozzolans, which could be a more viable alternative from a commercial standpoint when adopting these materials on an industrial scale
The compressive strength increased proportionally to the quantity of granulated blast furnace slag (GBFS), reaching a strength of up to 48.11 MPa after 28 days of curing at ambient temperature (25 °C) when the SiO2/Al2O3 ratio and GBFS % were 6.5 and 30%, respectively. If this value is compared with that reported for the simple system (NP) after 28 days of curing (12.96 MPa), the increase is 73%, which confirms that the reaction kinetics are positively affected by the addition of GBFS to the system and agrees with the results reported by other researchers [6, 13, 16, 21]
Summary
Geopolymers are a group of cementing ceramic materials belonging to the family of inorganic polymers that are obtained from the reaction between an aluminosilicate (primary precursor) and one alkaline activator These materials have been widely developed and have gradually attracted the attention of the scientific and industrial world as revolutionary materials. Despite the excellent properties obtained from the activation of industrial by-products and waste as precursors, the nature of these materials leads to variability in their chemical and mineral compositions, which makes it more difficult to standardise an activation process to obtain specific mechanical and durability properties These challenges have incentivised the development of studies focused on the production of alkaline activation cements based on different natural resources, such as clays ( kaolinites and smectites) and natural pozzolans, which could be a more viable alternative from a commercial standpoint when adopting these materials on an industrial scale
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