Factors influencing the compressive strength of fly ash based geopolymers

By M. Soutsos, A. Boyle, R. Vinai, Anastasis Hadjierakleous, S. Barnett. 2016

277 citations recorded by the source corpus.

Abstract Several factors affecting the reactivity of fly ash (FA) as a precursor for geopolymer concrete have been investigated. These include physical and chemical properties of various FA sources, inclusion of ground granulated blast furnace slag (ggbs), chemical activator dosages and curing temperature. Alkali-activated FA was found to require elevated curing temperatures and high alkali concentrations. A mixture of sodium hydroxide and sodium silicate was used and this was shown to result in high strengths, as high as 70 MPa at 28 days. The presence of silicates in solution was found to be an important parameter affecting strength. Detailed physical and chemical characterisation was carried out on thirteen FA sources from the UK. The most important factor affecting the reactivity was found to be the particle size of FA. The loss on ignition (LOI) and the amorphous content are also important parameters that need to be considered for the selection of FA for use in geopolymer concrete. The partial replacement of FA with ggbs was found to be beneficial in not only avoiding the need for elevated curing temperatures but also in improving compressive strengths. Microstructural characterisation with scanning electron microscope (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) was performed on FA/ggbs pastes. The reaction product of FA and ggbs in these binary systems was calcium aluminium silicate hydrate gel (C–A–S–H) with inclusion of Na in the structure.

Subfields: Building and Construction, Civil and Structural Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/7d6cd6370805fec96e08b89a96ca7adc006b50aa

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Citations in the corpus

Effect of slag content and activator dosage on the resistance of fly ash geopolymer binders to sulfuric acid attack (2018, background): “[117] when varying the alkaline activator dosages for fly ash GP mortars.”
Clean production and properties of geopolymer concrete; A review (2020, background): “H) gel for 100% FA can also improve the compressive strength of GeoPC (Soutsos et al., 2016).”
Guidelines for mix proportioning of fly ash/GGBS based alkali activated concretes (2017, methodology): “The relationship between strength and GGBS content has been reported to be almost linear [23].”
Use of Vietnamese rice husk ash for the production of sodium silicate as the activator for alkali-activated binders (2018, unknown): “Previous works suggested that the reactivity of FA is influenced mainly by average grain size, amorphous content and loss on ignition (Soutsos et al., 2016).”
Fly Ash-Based Geopolymer Binder: A Future Construction Material (2018, background): “[32], tentative mechanism of geopolymerization can be proposed by Scheme 2 [32].”
Sulfate and acid resistance of lithomarge-based geopolymer mortars (2018, background): “In terms of the precursor, the most common candidates are high purity kaolin [43, 44] and different types of clays [45-47], or waste/by-product materials, such as slags [40] and ashes [40, 48-50].”
Effects of slag substitution on physical and mechanical properties of fly ash-based alkali activated binders (AABs) (2019, background): “less free water is available for speciation of silica and alumina oligomers from the dissolution of fly ash [14].”
Production of sodium silicate powder from waste glass cullet for alkali activation of alternative binders (2019, unknown): “However, for room temperature cured mixes the reaction is driven by the GGBS and the relatively low sensitivity of GGBS to variations in M+ in the investigated range could explain this result [47].”