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Alkali-activated slag (AAS) paste: Correlation between durability and microstructural characteristics

Shariati, M ; Sharif University of Technology | 2021

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  1. Type of Document: Article
  2. DOI: 10.1016/j.conbuildmat.2020.120886
  3. Publisher: Elsevier Ltd , 2021
  4. Abstract:
  5. This study was aimed at evaluating the effects of alkali activator solution and utilization of silica fume (SF) on durability and microstructural characteristics of alkali-activated ground granulated blast furnace slag (GGBFS) pastes. The pastes were activated with sodium silicate (SS) blended with NaOH (SH) solution with molar concentrations of 8 M, 12 M, and 16 M and SS:SH ratios of 1.0, 2.5, and 4.0. The same mixes were prepared with SF as partial replacement of GGBFS at a dosage of 10% by weight. The initial and final water absorption as well as the electrical resistivity of the specimens were measured. The optimal paste fabricated with 12 M NaOH solution and SS:SH ratio of 2.5 showed the lowest water absorption and the highest electrical resistivity. Inclusion of SF reduced the final water absorption by 29% and increased the electrical resistivity by 62% compared to the same mix without SF. The observations were confirmed by the results of scanning electron microscopy (SEM) where the optimal paste showed a dense matrix with few pores. Furthermore, the chemical composition of the pastes was studied through energy-dispersive spectrometry (EDS) and X-ray diffraction (XRD) analyses. Moreover, the resistance to aggressive environment conditions of the pastes was examined through exposure to 5% hydrochloric acid and nitric acid up to 90 days. Generally, specimens were more resistant to nitrates. The specimens showed about 5–8% increase in their compressive strength compared to the unconditioned specimens during the first 28 days; however, up to 22% reduction in compressive strength was noticed after 90 days of exposure. It was shown that SS:SH ratio has a higher contribution to acid attack resistance of alkali-activated slag (AAS) pastes. © 2020
  6. Keywords:
  7. Acid resistance ; Atomic absorption spectrometry ; Blast furnaces ; Chemical analysis ; Compressive strength ; Durability ; Electric conductivity ; Hydrochloric acid ; Molar concentration ; Molar ratio ; Nitric acid ; Scanning electron microscopy ; Silica fume ; Silicates ; Slags ; Sodium hydroxide ; Aggressive environment ; Alkali activated slags ; Alkali activators ; Chemical compositions ; Energy dispersive spectrometry ; Ground granulated blast-furnace slag (GGBFS) ; Micro-structural characteristics ; Partial replacement ; Water absorption
  8. Source: Construction and Building Materials ; Volume 267 , 2021 ; 09500618 (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/abs/pii/S0950061820328919